An acoustic signal generator

专利摘要:
The present invention relates to an audio generator comprising, a first and a second transducer element, and the first transducer element has a first membrane having a surface which is non-flat, and a reflector, wherein the reflector has a surface with a non-flat contour and the reflector co-operating with directive guiding walls so as to lead and guide audio pressure waves to propagate in predetermined directions.
公开号:SE1250809A1
申请号:SE1250809
申请日:2012-07-10
公开日:2013-01-16
发明作者:Olle Ekedahl
申请人:Olle Ekedahl；
IPC主号:

专利说明:

An Acoustic Signal Generator Technical Field of the lnvention The present invention relates to an audio generator. The present invention also relates to a method for producing an audio generator.
Background Description of Related Art A common state of the art loudspeaker has a cone supporting a coil that can act as anelectromagnet, and a permanent magnet. The cone, which may be made by paper, istypically movable in relation to the permanent magnet. When an electric signal is deliveredto the coil, the coil acts as an electromagnet to generate a magnetic field acting on thepermanent magnet so as to cause the cone to move in relation to the permanent magnet.ln some sound reproduction systems, multiple loudspeakers may be used, eachreproducing a part of the audible frequency range. Miniature loudspeakers are found indevices such as radio and TV receivers, and many forms of music players. Largerloudspeaker systems are used for music reproduction e.g. in private homes, in cinemas and at concert arenas.
Summary lt is an object of the present invention to address the problem of achieving an improved audio generator for reproduction of sound waves.
According to an aspect of the invention, this problem is addressed by an audio generator(410, 190) comprising: a first transducer element (210A) being mounted such that the first transducer element(210A) can cause audio waves to propagate in a first direction (M); a second transducer element (210B) being mounted such that the second transducerelement (210B) may cause audio waves to propagate in a second direction which isdifferent to the first direction (M); an enclosure (310) adapted to enclose a space (320) betvveen the first transducer element(210A) and the second transducer element (210B); wherein the first transducer element (21 OA) has a first membrane (240A) having a surface (242A)which is non-flat, and wherein the first membrane (240A) has an outer perimeter (270) which is flexibly attached to a portion (282) of a transducer element body (280); said outer perimeter (270) 2 defining a first aperture (315) having a first aperture plane (314) ; and wherein, inoperation, the first membrane (240A) is adapted to cause said audio pressure waves topropagate in the first direction (M, 300, 300A,) orthogonal to said first aperture plane(314); wherein said audio generator (410, 190) further comprises a reflector (400), the reflector (400) having a surface (442) adapted to reflect acousticsignals; and directive guiding walls (510,520,530,540) the reflector (400) co-operating with the directive guiding walls so as to lead and guidesaid audio pressure waves to propagate in a second direction (300'); said seconddirection (300') being different from said first direction; and wherein the acoustically reflective surface (442) has a non-flat contour (242').
Since the two membranes will move in the same direction at the same time they willeffectively interact in a co-operative manner so as to defeat any mechanical resistance tomembrane movement. Advantageously, air trapped in between the membranes will movewith the movement of the membranes. Moreover, this solution eliminates or significantlyreduces any air pressure variations in the space within the enclosure. Air being acompressible medium, such air pressure variations in the space 320 within the enclosure310 may othenNise lead to a spring-like force acting on the membrane, which could leadto slower response and hence to distortion. Hence, whereas state of the art transducersfor transforming an electric speaker drive signal into an acoustic signal inherently cause adistortion such that the acoustic signal generated by a state of the art transducer fails totruly represent the electric speaker drive signal, this solution advantageously enables thefirst transducer element membrane to provide an improved degree of fidelity in the senseof correctly representing the electric speaker drive signal. Accordingly, when the electricspeaker drive signal is such as to provide a high degree of fidelity in the sense of correctlyrepresenting an original acoustic signal this solution advantageously enables the firsttransducer element membrane to provide an improved degree of fidelity in the sense of correctly representing the original acoustic signal.
The non-flat contour of the reflector may cooperate with the non-flat membrane so as tocause reflection of the sound such that tNo acoustic waves W1' and W2', being created atmutually different positions on the membrane will have travelled substantially the same distance when they reach the plane of the second aperture. Hence, the sound waves delivered from the second aperture of the audio generator may advantageously be truly plane sound waves.
Accordingly, the provision of two cooperating transducer elements advantageouslyinteract with the provision of a reflector having non-flat contour so as to enable the audiogenerator to provide an improved degree of fidelity in the sense of correctly representingthe original acoustic signal, when the electric speaker drive signal is such as to provide ahigh degree of fidelity in the sense of correctly representing an original acoustic signal.According to an embodiment, the enclosure is a sealed enclosure.
Additional aspects of the invention are discussed below in this document, and various embodiments, as well as advantages associated thereto are disclosed.
Brief Description of the Drawinqs For simple understanding of the present invention, it willbe described by means of examples and with reference to the accompanying drawings, of which Figure 1 shows a schematic block diagram of a first embodiment of a system 100 according to the present invention.
Figure 2A is a schematic side view of an embodiment of an electro-audio transducer.
Figure 2B is a schematic side view of another embodiment of an electro-audio transducer.
Figure 2C is a schematic side view of another embodiment of an electro-audio transducer.
Figure 2D is a schematic cross-sectional view taken along line A-A of FIG 2C.Figure 3 is a schematic side view of an embodiment of a transducer element.Figure 4 is a schematic side view of an embodiment of a transducer element.Figures 5 and 6 are schematic side views of embodiments of an audio generator.Figure 7A is also a schematic side view of an embodiment of an audio generator.Figure 7B is a top view of an embodiment of a transducer element.
Figure 7C is a side view of an embodiment of an audio generator 410 including atransducer element 210, as illustrated in Figure 7B, and an embodiment of acorresponding reflector 400.
Figure 7D is a perspective side view of the audio generator illustrated in Figure 7C.Figures 8A-8F illustrated an embodiment of a process for the design of an audio reflector.
Figure 8G is another sectioned lateral view of an audio generator. 4 Figure 9 illustrates an audio generator including plural electro-audio transducers 410|, 410.., and 410m for correctly transforming an electrical signal to a series of pressure waves.
Figure 10A is an illustration of yet an embodiment of an audio generator.Figure 10B is a cross-sectional top view taken along line A-A of FIG 10A.
Figure 11A is an illustration of yet an embodiment of an audio generator.
Detailed Description of Embodiments Fig. 1 shows a schematic, exemplifying system 100 according to the present invention.The system 100 is adapted to reproduce sound waves. The system comprises a soundsource 105 adapted to emit an original acoustic signal 110. The original acoustic signal isformed by sound waves. One example of a sound source 105 is a vocalist. The vocalistemits an original acoustic signal 110 while singing a song. Another example of the soundsource 105 emitting an original acoustic signal 110 is a speaker giving a speech. Yetanother example of a sound source 105 emitting an original acoustic signal 110 is anorchestra performing a piece of music. This description will discuss sound sources 105emitting an original acoustic signal 110 audible to human beings and the reproduction ofsuch sounds, but the present invention could also be applied to systems 100 comprisingsound sources 105 emitting other acoustic signals, such as e.g. acoustic signals formed by subsonic sound waves or ultrasonic sound waves.
The system 100 further comprises a transducer 115, such as e.g. a microphone 115,adapted to transform the original acoustic signal 110 into a microphone signal. Themicrophone is adapted to receive the original acoustic signal 110 by letting the soundwaves exert a force on the microphone's 115 moving element. The microphone 115 isfurther adapted to create the microphone signal 120 formed by an electrical voltage signalbased on the vibrations of the microphones moving element. The level or amplitude of themicrophone signal 120 is normally very low, typically in the microvolt range, for example0-100 pV. The microphone 115 may be a capacitor microphone having a flat plate which may be set in motion in response to air pressure deviations caused by acoustic waves.
The system 100 may further comprise a microphone preamplifier 125 adapted to output a microphone line level signal 130 with a greater level than the microphone signal 120. The level of the microphone line level signal 130 is typically in the volt range, for example 0-10V. 5 The system 100 may optionally comprise a signal treater 135. The signal treater 135 mayinclude an analogue-to-digital converter, ADC, adapted to generate a first digital signal140 in response to the microphone signal 120 so that the first digital signal 140 is a digitalrepresentation of the microphone signal 120. The signal treater 135 may also includedigital processing of the microphone line level signal 130. The signal treater135 is further adapted to output the first digital signal 140.
The system 100 may also comprise a signal storage device 145 adapted to store eitherthe analogue microphone line level signal 130, or if a signal treater 135 is present in thesystem 100, the first digital signal 140. The first digital signal 140 may be stored on a datacarrier 142, such as a non-volatile memory. The non-volatile memory may be embodiedas a magnetic tape, hard-drive, or compact disc. The signal storage device 145 may alsohave an output for delivery of a signal 150 retrieved from the data carrier 142.Alternatively the stored signal may be retrieved by a separate device for retrieval of astored signal from the data carrier 142. Such a separate device may be embodied e.g. by a tape player or compact disc player.
The system further comprises a preamplifier 155 adapted to prepare either themicrophone line level signal 130, or if a signal treater 135 is present the processedmicrophone signal 140, or if a signal storage 145 is present the stored signal 150 forfurther processing or amplification. The preamplifier is further adapted to adjust the levelof the input signal (130, 140 or 150). The preamplifier 155 is further adapted to output aline signal 160 based on the input signal (130, 140 or 150).
The system may optionally comprise a signal handler 165 adapted to process the line signal 160. The signal handler may include an optional D/A-converter, when the system100 is adapted for digital sound. The signal handler may also optionally include a signalprocessor, which may be implemented in a mixer board. The signal handler165 has an output for delivery of a second line level signal 170.
The system further comprises a amplifier 175 adapted to generate an electric speakerdrive signal 180 for delivery on an amplifier output 178. According to an embodiment ofthe invention the amplifier175 is a power amplifier 175. The speaker driver signal 180may be generated in response to the line level signal 160, or if a signal processor 165 ispresent in the system 100, in response to the processed second line level signal 170. ln this manner, the power amplifier may generate an analogue electric signal 180 such that a time portion of the analogue electric signal 180 has the same, or substantially the same,wave form as the corresponding time portion of the microphone signal 120. According toan embodiment the electric speaker drive signal 180 may be delivered to an input 185 ofan electro-audio transducer 190. The electro-audio transducer 190 operates to generatean acoustic signal 200 in response to the electric speaker drive signal 180 received on theinput 185. The acoustic signal 200, which may include e.g. music, may be heard by a user205.
As mentioned above, an audio/electric transducer 115, such as a microphone, mayoperate to transform an acoustic signal 110 (Se Fig 1) into an electric microphone signal120. There exist state of the art transducers which are capable of transforming anacoustic signal 110 into an electric microphone signal 120 such that the electricmicrophone signal 120 has a high fidelity in the sense of correctly representing theacoustic signal 110. However, state of the art transducers for transforming an electricspeaker drive signal 180 into an acoustic signal inherently cause a distortion such that theacoustic signal generated by a state of the art transducer fails to truly represent theelectric speaker drive signal 180. ln effect, state of the art sound reproductionsystems inherently fail to generate an acoustic signal which truly represents theoriginal acoustic signal 110. Hence, even when the electric speaker drive signal 180is such as to provide a high degree of fidelity in the sense of correctly representingthe acoustic signal 110, state of the art loud speakers inherently introducedistortion such that sound generated by the state of the art loud speaker has alower degree of fidelity in the sense of correctly representing the acoustic signal 110 than the electric speaker drive signal 180.
Figure 2A is a schematic side view of an embodiment of an electro-audiotransducer190.The electro-audio transducer 190 includes a first transducer element 210A and a secondtransducer element 210B, and a baffle 230.
Figure 3 is a schematic side view of an embodiment of a transducer element 210 whichmay be used in the electro-audio transducers discussed in this document. The transducerelement 210 has a membrane 240 including means 250 for causing the membrane 240 tomove in dependence on an electric input signal. The membrane movement generator 250may include a coil 250 adapted to generate a magnetic field in response to reception of adrive signal, such as drive signal 180, Which may be delivered via drive terminals 252 and 254. The transducer element 210 may also include a permanent magnet 260 which is firmly attached to a transducer element body 280. The membrane 240 has an outerperimeter 270 which may be flexibly attached to a portion 282 of the transducer elementbody 280. The flexibility may be attained by a flexible member 284 being adapted tophysically connect the outer perimeter 270 of the membrane 240 with the portion 282 ofthe transducer element body 280. The drive terminals 252 and 254 may be electricallyconnected to the coil 250 by electrical conductors 256 and 258, respectively, beingadapted to allow the desired movement of the membrane 240 while allowing the terminals252 and 254, respectively, to remain immobile in relation to the transducer element body280. The transducer element body 280 may be attachable to the baffle 230.
The membrane 240 is movable in relation to the transducer element body 280 in responseto the drive signal 180. When the electric signal 180 is delivered to the coil, the coil actsas an electromagnet to generate a magnetic field which, when interacting with themagnetic field of the permanent magnet 260, generates force such that the membrane240 moves in relation to the permanent magnet 260. The transducer element 210 isadapted to cause the membrane 240 to move only, or substantially only, in the direction ofarrow 300 in Figure 2, while holding membrane 240 immobile, or substantially immobile, inall directions perpendicular to the direction of arrow 300. ln this manner the membrane240 may cause audio waves to propagate in the direction of arrow 300 (See Figure 3), away from membrane 240, when a variable electric signal 180 is delivered to the coil 250.
The direction of arrow 300, in Figure 3, may be orthogonal to the plane 314 of a firstaperture 315. The first aperture 315 may be defined by the outer perimeter 270 of themembrane 240. When the membrane 240 is cone shaped, the first aperture plane 314 may be defined by the base of the membrane cone 240.
Hence, the transducer element 210 may be adapted to cause the membrane 240 to moveonly, or substantially only, in a direction 300 orthogonal to the plane 314 of a first aperture315, while holding the membrane 240 immobile, or substantially immobile, in all directions parallel to the plane 314 of a first aperture 315.
According to an embodiment the membrane 240 is made of a light weight material havinga certain degree of stiffness. According to an embodiment membrane 240 is cone-shaped,as illustrated in Figure 3. The material, of which the cone-shaped light weight membrane 240 is made, may include paper.
Referring to Figure 2A, the electro-audio transducer 190 includes the first transducerelement 21 OA being mounted to the baffle 230 such that the first transducer element 21 OAmay cause audio waves to propagate in the direction of arrow 300A. Additionally theelectro-audiotransducer190 includes a second transducer element 210B being mountedsuch that the second transducer element 210B may cause audio waves to propagate in the direction of arrow 300B, that is in the direction opposite to the direction of arrow 300A.
The electro-audio transducer 190 includes an enclosure 310 adapted to enclose a space320 between the first transducer element 21 OA and the second transducer element 210B.According to an embodiment the enclosure 310 is a sealed enclosure. Hence, theenclosure 310 has a body 312 so that the body 312 cooperates with the membranes 240Aand 240B so as to prevent air from flowing freely between the air volume within the enclosure 310 and the ambient air.
The two transducer elements 210A and 210B may advantageously be connected inreverse phase, as illustrated in Figure 2A. Accordingly, a positive terminal 330 of amplifieroutput 178 may be connected to the positive terminal 252A of transducer elements 210Aand to the negative terminal 254B of transducer element 210B; and a negative terminal340 of amplifier output 178 may be connected to the negative terminal 254A of transducerelement 210A and to the positive terminal 252B of transducer element 210B. This reversephase connection has the effect that when membrane 240 A moves in the direction ofarrow 300A, then also membrane 240B moves in the direction of arrow 300A. When theenclosure 310 is a sealed enclosure 310, and the two transducer elements 210A and210B are connected in reverse phase, then the air trapped in between the membranes willmove with the movement of the membranes 240A and 240B. Since the two membraneswill move in the same direction at the same time they will effectively interact in a co-operative manner so as to defeat any mechanical resistance to membrane movement.Moreover, this solution eliminates or significantly reduces any air pressure variations inthe space 320 within the enclosure 310. Air being a compressible medium, such airpressure variations in the space 320 within the enclosure 310 may otherwise lead to aspring-like force acting on the membrane, which could lead to slower response and hence to distortion.
When the transducer element210 is designed so that the coil can move between positionswith mutually different magnetic field amplitude, the force, generated by a certain electric current amplitude in the coil, may be weaker when the coil is in a position where it experiences weaker magnetic field amplitude, as compared to the force, generated by thatcertain electric current amplitude in the coil when the coil is in a position where it experiences stronger magnetic field amplitude.
Advantageously, when the tNo transducer elements 210A and 210B are connected inreverse phase, as illustrated in Figure 2, the coils 250A and 250B will be in mutuallydifferent positions, i.e. if coil 250A experiences weaker magnetic field amplitude then coil250B will be in a position to experience a stronger magnetic field amplitude. Accordingly,the electro-audio transducer 190 including first transducer element 21 OA and secondtransducer element 210B such that when membrane 240A moves in the direction of arrow300A, then also membrane 240B moves in the direction of arrow 300A, advantageouslyrenders an electro-magneto-mechanical interaction between the transducer elements210A and 210B. According to an embodiment, referring to figure 3 in conjunction with Fig2 for example, when the coil 250A is far away from the magnet 260A so as to experiencea relatively weak magnetic field amplitude then coil 250B will be close to the magnet 260B so as to experience a stronger magnetic field amplitude.
Figure 2B is a schematic side view of another embodiment of an electro-audio transducer190. The Figure 2B embodiment may be substantially as described in connection withFigure 2A, but with the following modifications: According to the Figure 2B embodiment,the enclosure 310 may be a sealed enclosure, wherein a body 312 of the enclosure 310includes means 318 for air pressure equalization. According to an embodiment, themeans 318 for air pressure equalization may include a valve 318, the valve beingopenable so as to allow an equalization of air pressure between the air volume within theenclosure 310 and the ambient air, and closeable so as the make the enclosure 310 is a sealed enclosure. ln this context it is noted that the ambient air pressure may vary due to weather conditions,causing e.g. so called low pressures or high pressures. Also, when the electro-audiotransducer 190 has been transported between different geographical places or altitudes,such as e.g. from a place near sea level to another place a couple of hundred meters above sea level, the ambient air pressure will have changed.
The means 318 for air pressure equalization advantageously allows for an equalization ofthe air pressures to be performed, e.g, prior to use of the electro-audio transducer 190 for production of of acoustic signals 200 (See Fig 1 in conjunction with Fig 2B). Accordingly, the provision of a means 318 for air pressure equalization advantageously allows foroptimum operation of the electro-audio transducer 190, irrespective of weather and geographical position.
According to another embodiment, the means 318 for air pressure equalization may include a throttling means 318, adapted to allow a very slow equalization of air pressurebetween the air volume within the enclosure 310 and the ambient air. ln this context it isnoted that the throttling means 318 may include a minute passage adapted to allow for a very slow equalization of air pressure As mentioned in connection with Figure 2A, the two transducer elements 210A and 210Bmay advantageously be connected in reverse phase. Whereas Figure 2A illustrates anembodiment wherein the two transducer elements (210A, 210B) are connected in parallel,Figure 2B illustrates an embodiment wherein the two transducer elements (210A, 210B) are connected in series.
The sound waves exciting via the aperture 315A of transducer element 21 OA maypropagate into the surrounding space primarily in the direction 300A. However, the natureof sound waves is such that they may spread somewhat also in other directions than thedesired direction 300A, in a constellation as illustrated in Figure 2A or 2B. According to anembodiment of the invention, however, the audio generator 410 may also include directive guiding walls so as to cause an increased sound propagation focus in the direction 300A.
Figure 2C is a schematic side view of another embodiment of an electro-audio transducer190. The Figure 2c embodiment may be substantially as described in connection with Figure 2A and/or 2B, but with the following modifications: The electro-audio transducer 190 according to the Figure 2C embodiment may include abox structure 502. The box structure 502 holds the enclosure 310, which may be asdescribed above. Moreover, box structure 502 includes directive guiding walls 510, 520,530 and 550 adapted to lead and guide said audio pressure waves so as to focus thedirection of propagation of the audio pressure waves caused by the transducer element210A in the direction M, 300A. 11 The box structure 502 may also be provided with a means 318 for air pressureequalization, as described above, and it may have an opening 319 or so called slave base element 319.
Figure 2D is a schematic cross-sectional view taken along line A-A of FIG 2C.
Hence, when movement of the membrane 240A causes a momentary increase in airpressure, i.e. a pressure pulse, having a direction of propagation vin the direction M,orthogonal to the plane of the first aperture plane 315, the pressure pulse is maintainedand directed by the directive guiding walls 510, 520, 530 and 550 so as to focus thedirection of movement of the pressure pulse in the direction 300A' towards a plane P at a distance from the audio generator 410.
Since a listener 205 will typically enjoy music at a distance D3 of more than one meter, orso, from the audio generator 410, it is advantageous to have the sound (which is composed of successive controlled pressure pulses) directed.
When a plane wave front of narrow width leaves a source, it will inherently spreadsideways in a manner that causes the resulting wave front to be curved at a large distancefrom the source. ln this connection, the directive guiding walls operate to lead and guide the successive pressure pulses as they propagate from the first aperture.
A PHASE ADJUSTING REFLECTOR Figure 4 is a schematic side view of an embodiment of a transducer element 210. Thetransducer element 210 illustrated in Fig. 4 may be designed e.g. as described withreference to Fig. 3 above. This transducer element 210 may be used in the electro-audiotransducer 190 of Fig.2. As mentioned above, the transducer element 210 is adapted tocause the membrane 240 to move only, or substantially only, in the direction of arrow 300(See Fig 4 and Fig 3) so as to cause audio waves to propagate in the direction of arrow300, away from membrane 240, when a variable electric signal 180 is delivered to themembrane movement generator 250. The membrane movement generator 250 may include a coil 250, as mentioned above.
Hence, the direction of sound propagation is in the direction of arrow 300, which is thenormal vector to the plane P in Figure 4, i.e. the direction of sound propagation is primarilyin the direction of membrane movement. Accordingly, when: the spatial shape of the membrane is not parallel to the plane P, then: two acoustic waves W1 and W2, 12 respectively, may be created at mutually different distances D1 and D2, respectively,from the plane P. The inventor realized that the two acoustic waves W1 and W2, beingcreated at mutually different positions 360 and 370, respectively, will lead to distortion ofthe sound, as experienced by a user having an ear at a position along the plane P (SeeFig 4). ln fact, the inventor realized that when the spatial shape of the audio generatingmembrane 240 is not parallel to a plane P at a distance Ds from the from the front portion282 of a transducer element 210, some frequencies may be suppressed and otherfrequencies may be accentuated, as experienced at any distance D3 from the front portion282 of a transducer element 210 (See Fig. 4 and/or Fig. 2).
According to the Figure 4 embodiment, the membrane 240 is, at least in part, cone-shaped. Hence, the spatial shape of the membrane is not parallel to a plane P (See Fig 4)which is orthogonal to the direction of sound propagation. With reference to Figure 4, thearrow 300 may be normal to the plane P, as illustrated by the angle at reference 350 inFig 4, being a 90 degree angle. Hence, two acoustic waves W1 and W2, respectively, ofthe same frequency f1 being created at mutually different positions 360 and 370,respectively, will be offset in phase in relation to each other. This phase offset, or phasedeviation, is indicated as cp. The inventor realized that, for each particular constituentfrequency in the generated audio signal 200 (See Fig 1) the phase deviation cp dependson the distance deviation dD= D2-D1 (See Figure 4 in conjunction with Figure 1). This isdue to the fact that a signal having a certain frequency f1will exhibit a corresponding wavelength A1 as it travels through air (See Figure 4). For example, a 10 kHz acoustic signaltravelling through air exhibits a wave length of about 34 mm, whereas a 100 Hz signal travelling through air exhibits a wave length of about 3400 mm, i.e. about 3,4 meters.
When the membrane 240 is in the shape of a truncated cone, as illustrated in Figure 4,the maximum distance deviation dD= D2-D1 varies in dependence on the radius R of the cone-shaped membrane 240.
Accordingly, the inventor devised a solution addressing the problem of achieving an improved electro-audio transducer.
With reference to Figure 1, the inventor devised a solution addressing the problem ofachieving an improved electro-audio transducer having a higher degree of fidelity in the sense of correctly representing the original acoustic signal 110 when the electric speaker 13 drive signal 180 is such as to provide a high degree of fidelity in the sense of correctly representing the original acoustic signal 110. ln particular, the inventor devised a solution addressing the problem of achieving animproved electro-audio transducer which eliminates, or substantially reduces distortion ofthe sound, as experienced by a user having an ear at a position along a plane P at a distance D3 from the electro-audio transducer 190 (See Fig 1, 3 or 4).
An original acoustic signal 110 may include plural signal frequencies, each of which ismanifested by a separate wave length as the acoustic signal 110 travels through air. lnorder to regenerate an acoustic signal 200 which truly represents the original acoustic signal 110 (See Fig.1) the following conditions apply: A) The mutual temporal order of appearance, between any two signals in the originalacoustic signal 110 must be maintained in the reproduced acoustic signal 200.
B) The mutual amplitude relation, between any two signals in the original acoustic signal110 must be maintained in the reproduced acoustic signal 200.
The above condition A) may be scrutinized for at least two cases: A1) The mutual temporal order of appearance, between any two siqnals havinq the samesignal freguency in the original acoustic signal 110, must be maintained in the reproducedacoustic signal 200 (compare Figure 4 and 6). lf condition A1 is n_otfulfilled, the effect istwo-fold: Firstly, the duration of that particular reproduced acoustic signal frequencyf1200 will be extended as compared to the original acoustic signal f1110. The temporalextension TEXT will be approximately TEXT = dD/v wherein dD = D2-D1, andv= the speed of the acoustic signalFor sound reproduction, the speed v of the acoustic signal in air at room temperature andat normal air humidity is about 340 metres per second. This temporal extension TEXT iscaused since a single electrical drive signal 180 having a frequency f1 with a distinct starttime tSTART, and a distinct end time tEND, will cause the state of the art loud speaker toproduce plural acoustic signals (See Figure 4). lt can be deduced, e.g. from theillustration of Figure 4, that a front edge of a wave W1, will reach the plane P earlier than the front edge of another wave W2, since the wave W1 started from a position closer to 14 the plane P. This may be experienced, by a listener at plane P, as a smearing of theacoustic signal.
Secondly, the phase deviation cp, as illustrated in Figure 4, may cause thewave W1 to interact with the wave W2 at the plane P under the principle of superposition.ln very brief summary, the superposition principle, also known as superposition property,states that, for all linear systems, the net response at a given place and time caused bytwo or more stimuli is the sum of the responses which would have been caused by eachstimulus individually. Acoustic waves are a species of such stimuli. Waves are usuallydescribed by variations in some parameter through space and time-for example, heightin a water wave, or the pressure in a sound wave. The value of this parameter is referredto as the amplitude of the wave, and the wave itself is a function specifying the amplitudeat each point in a space filled with air, such as e.g. a room. An arbitrary point in the plane P (See Figure 4) is an example of such a point in space.
When the superposition principle is applied to the pressure in a sound wave, thewaveform at a given time is a function of the sources and initial conditions of the system.An equation describing a sound wave may be regarded as a linear equation, and hence,the superposition principle can be applied. That means that the net amplitude caused bytwo or more waves traversing the same space, is the sum of the amplitudes which wouldhave been produced by the individual waves separately. Hence, the superposition ofwaves causes interference between the waves. ln some cases, the resulting sum variationhas smaller amplitude than the component variations. ln other cases, the summedvariation will have higher amplitude than any of the components individually. Hence, abreach of the above condition A1 may result also in a breach of the above condition B.A2) The mutual temporal order of appearance, between any two signals having thedifferent signal frequencv in the original acoustic signal 110, must be maintained in thereproduced acoustic signal 200. When an original acoustic signal 110 includes twoseparate signal component frequencies f1 and f2, e.g. one treble signal componentincluding a frequency f1 of 10 000 Hz and another signal component including afrequency f2 of 50 Hz, a system for reproduction of acoustic signals may attempt toreproduce this multi-component acoustic signal 110, using separate transducer elements,such as a tweeter transducer element for reproducing the high frequency component f1and a base transducer element for reproducing the low frequency component f2. ln this connection, please see discussion below in connection with Fig 9.
When the membrane 240 is in the shape of a truncated cone, as illustrated in Figure 4,the maximum distance deviation dD= D2-D1 depends on the radius R of the cone-shapedmembrane 240, as mentioned above. When the membrane 240 is cone-shaped, the outerperimeter 270 of the membrane 240 is circular with a radius R1 defining the base of the membrane cone.
With reference to Figure 5, there is provided an audio generator 390 having amembrane 240 including a membrane movement generator 250 for causing themembrane 240 to move in dependence on an input signal. The surface 242 of themembrane 240 is such that there exists a vector V which is normal to the membranesurface while said vector V is unparallel to the primary direction M of movement ofthe membrane 240. Hence, the primary direction M of movement of the membrane 240 coincides with the direction 300 of propagation of audio waves away from membrane 240, when a variable electric signal 180 is delivered to the membrane movement generator 250.
This is fundamental, of course, since the audio waves are created by the movement of the membrane 240.
The audio generator 390 includes a reflector 400 adapted to cause reflection of the soundsuch that two acoustic waves W1' and W2', being created at mutually different positions360' and 370', respectively, on the membrane 240 will have travelled substantially thesame distance when they reach a plane P at a distance D3 from audio generator 390.According to an embodiment, the distance D3 is much larger than the largest distance from the surface of the membrane to the surface of the reflector.
The audio generator 390 may also include a baffle, schematically illustrated with reference230 in Fig 5. ln this manner the audio generator 390, 410 may cause audio waves to propagate in thedirection of arrow 300' towards the plane P (See Figure 5 and/or 6), when a variableelectric drive signal 180 is delivered to the membrane movement generator 250. Theouter perimeter 270 of the membrane 240 defines the first aperture 315 through which theacoustic signal will flow, when the transducer element 210 is in operation. ln effect, a rayof the acoustic signal generated at point 360' of the membrane 240 may travel in thedirection of arrow M (See Figure 5), i.e. in a direction orthogonal to the plane 314 of the first aperture 315. 16 When reflected in the direction towards plane P, the wave will pass a second aperture 415of the audio generator 390, 410 (See Figure 5). With reference to figure 5, the plane 416of second aperture 415 is perpendicular to the plane of the paper and perpendicular to thedirection of arrow 300”. The second aperture 415 stretches from a point 450 substantiallyat the perimeter 270 of membrane 240 to a point 450”. As illustrated by Figure 5, thesound ray W1' as well as the sound ray W2' pass through the second aperture 415. Theref|ector 400 may be “tailor-made” to cooperate with membrane 240 so as to causereflection of the sound such that tvvo acoustic waves W1' and W2', being created atmutually different positions 360' and 370', respectively, on the membrane 240 will havetrave|ed substantially the same distance when they reach the plane 416 of the second aperture 415. Hence, the sound waves delivered from the second aperture 415 of the audio generator 390, 410 (See Figure 5) may advantageously be truly plane sound waves.
Moreover, directive guiding walls 510, 520, 530, 540, similar to, or of same design asdescribed above in connection with Figure 2C and D may be provided. The directiveguiding walls are schematically illustrated in Figure 5 by the guiding wall 520 extending beyond the upper edge 450' of the second aperture 415.
Figure 6 is a schematic side view of an embodiment of an audio generator 390, 410. Theaudio generator 390, 410 of Figure 6 may be as described with reference to Figure 5above. The audio generator 390, 410 may include a transducer element 210, as describedin connection with Figure 3 above. The audio generator 410 may include a membrane 240having a surface 242 which is non-flat, a baffle 230; and a ref|ector 400, wherein the ref|ector 400 has a surface shape adapted to reflect audio waves propagating from themembrane surface such that a phase deviation cp, between two audio waves, caused bysaid non-flat surface 242 is substantially eliminated at an arbitrary distance D3 from theaudio generator 410. This advantageous effect, attained by the audio generator 390 ofFigure 5 and the audio generator 410 of Figure 6, may be readily understood by looking atFigure 6, and comparing with Figure 4. Hence, the phase deviation cp, between two audiowaves W1' and W2', respectively, caused by the non-flat surface 242, may besubstantially eliminated at an arbitrary distance D3 from the audio generator 410. This isdue to the fact that the two acoustic waves W1' and W2', being created at mutuallydifferent positions 360' and 370', respectively, on the membrane 240, will have trave|ed substantially the same distance when they reach a plane P at a distance D3 from audio 17 generator 390 when the reflector 400 has a surface 442 adapted to reflect acousticsignals and the acoustically reflective surface 442 has a non-flat contour which has been defined in dependence on the contour of the non-flat surface 242 of the membrane 240.
As clearly shown in Figure 6, when an audio wave W1' travels along a straight line A1 inthe direction M (See Figure 6 in conjunction with Figure 5) from the position 360' on themembrane surface 242, it will hit the surface 442 of reflector 400 at a point denoted 360",where it may be reflected in a direction 300' towards plane P. A user/listener 205 may bepositioned at plane P, as schematically indicated by an ear in Figure 6. The distancetravelled by audio wave W1' from the position 360' to the plane P is the sum of distancesA1 + A2. ln a corresponding manner, the distance travelled by audio wave W2' from theposition 370' to the plane P is the sum of distances B1 + B2. Hence, audio wave W1' willtravel a first distance DW1- = A1 + A2, and audio wave W2' will travel a second distanceDWZ- = B1 + B2.
According to an embodiment of the invention, the contour of the non-flat reflector surface442 may be such that the first distance DW1- is substantially equal to the second distance DWZ, as clearly shown in Figure 6. ln this connection it is to be noted that the substantially straight lines A1 and A2, in figure6, illustrate a path travelled by a ray W1' of sound whose starting point on the surface 242of membrane 240 is the point denoted 360'. Similarly, the substantially straight lines B1and B2, in figure 6, illustrate a path travelled by another ray W2' of sound whose starting point on the surface 242 of membrane 240 is the point denoted 370'.
Moreover, as mentioned above, a sound wave travelling through air may be described byvariations in the air pressure through space and time. The air pressure value may bereferred to as the amplitude of the sound wave, and the wave itself is a function specifyingthe amplitude at each point in the space filled with air. An arbitrary point in the plane P(See Figure 6) is an example of such a point in space. With reference to figure 6, the sinewave-shaped line W1A' provides a schematic illustration of the spatial variation of theamplitude of the sound ray W1' originating at the point denoted 360' on the surface 242 ofmembrane 240, and the sine wave-shaped line WZA' provides a schematic illustration ofthe spatial variation of the amplitude of the sound ray W2' originating at the point denoted370' on the surface 242 of membrane 240. Hence, a signal having a certain frequency f1will exhibit a corresponding wave length A1 as it travels through air (See Figure 6 in 18 conjunction with Figure 4). For example, a 10 kHz acoustic signal travelling through airexhibits a wave length of about 34 mm, whereas a 100 Hz signal travelling through airexhibits a wave length of about 3400 mm, i.e. about 3,4 meters. As illustrated in Figure 6,the audio generator 390, 410 may provide the advantageous effect of reducing orsubstantially eliminating distortion of sound caused by interference. This advantageouseffect may be attained because, according to some embodiments of the invention, thecontour of the non-flat reflector surface 442 is adapted to compensate for the non-flatsurface (242) of the membrane 240 by substantially equalizing the distance of travel formutually different rays of acoustic signals. This equalization may thus ensure that e.g.when plural rays, such as W1' and W2', of the acoustic signal has a certain frequency f1, hence exhibiting a corresponding wave length A1, the amplitudes W1A' and W1B' of the acoustic signal rays will be substantially in phase with each other, as illustrated in Figure 6.
As mentioned above, the contour of the non-flat reflector surface 400 may be adapted tocompensate for the non-flatness of the surface 242 such that the first distance DW1- issubstantially equal to the second distance DW2. Hence, a phase deviation cp, between tNoaudio waves W1' and W2', respectively, caused by the non-flat surface 242, may besubstantially eliminated at an arbitrary distance D3 from the audio generator 410, sincetwo acoustic waves W1' and W2', being created at mutually different positions 360' and370', respectively, on the membrane 240 will have travelled substantially the same distance when they reach a plane P at a distance D3 from audio generator 390.
Hence, the phase deviation cp, between two audio waves W1' and W2', respectively,caused by the non-flat surface 242, may be substantially eliminated at an arbitrarydistance D3 from the audio generator 410, since two acoustic waves W1' and W2', beingcreated at mutually different positions 360' and 370', respectively, on the membrane 240will have travelled substantially the same distance when they reach a plane P at adistance D3 from audio generator 390.
Thus, the audio generator 390, 410 (See figure 5 and/or 6) may advantageously ensurethat when the electric drive signal 180 includes a single electric frequencycomponent fmgo having a certain amplitude Amgo for a certain duration tmgo, thenthe acoustic signal 200, as it appears at an arbitrary point at the plane P at a distance D3 from the baffle 230, will exhibit a corresponding single acoustic frequencycomponent fnzoo having a certain acoustic amplitude Anzoo for a certain acoustic duration tnzoo; wherein 19 the single acoustic frequency component fnzoo will be equal to, or substantially equal tothe single electric frequency component fmgo, and the certain acoustic amplitude Anzoo will correspond to, or substantially correspond tothe certain amplitude An180, and the certain acoustic duration tnzoo will be equal to, or substantially equal to the certainduration tmgo. Hence, interference caused by superposition which inherently result from astate of the art loudspeaker having a non-flat surface may be reduced, or substantiallyeliminated by the use of an embodiment of an audio generator 390, 410 as described inconnection with figure 5 and/or 6.
Figures 7-11 illustrate and describe further embodiments and details of embodiments of the invention.
Figure 7A is also a schematic side view of an embodiment of an audio generator 410.The audio generator 410 may include a transducer element 210, as described inconnection with Figure 3 above. The audio generator 410 comprises a membrane 240having a surface 242 which is non-flat, and a reflector 400, wherein the reflector 400 has asurface shape adapted to reflect audio waves propagating from the membrane surface242 such that a phase deviation, between two audio waves, caused by said non-flatsurface 242 is substantially eliminated at an arbitrary distance D3 from the audio generator 410.
Figure 7B is a top view of an embodiment of a transducer element 210. The transducerelement 210 illustrated in Figure 7B may be designed substantially as described inconnection with Figure 3 above. Hence, transducer element 210 may have a membrane240 which is movable in dependence on an electric drive signal 180. The membrane 240has an outer perimeter 270 which may be flexibly attached to a portion 282 of the transducer element body 280. ln the embodiment of Figure 7B, the outer perimeter 270 of the membrane 240 is circular,having a radius R1. Hence, the flexible member 284, which may be adapted to physicallyconnect the outer perimeter 270 of the membrane 240 with a portion 282 of the transducerelement body 280, may have an inner radius R1, and an outer radius R2.
Accordingly, the portion 282 of the transducer element body 280 may have an inner radius R2 and an outer radius R3, as illustrated in Figure 7B.
Figure 7C is a side view of an embodiment of an audio generator 410 including atransducer element 210, as illustrated in Figure 7B, and an embodiment of a corresponding reflector 400.
Figure 7D is a perspective side view of the audio generator 410 illustrated in Figure 7C.A PROCESS FOR DESIGNING A PHASE ADJUSTING REFLECTOR An embodiment of a process for the design of an audio reflector 400 is described withreference to Figures 8A to 8F Figure 8A is a schematic side view of a transducer element 210 having a membrane 240and a first aperture 315. The first aperture 315 may be as discussed above in connectionwith figures 3 and/or 5 and/or 6. Hence, the first aperture 315 may be defined by the outerperimeter 270 of the membrane 240. The membrane 240, according the Figure 8Aembodiment, is substantially cone shaped. Accordingly, the upper surface 242 of themembrane 240, as illustrated in Figure 8A, may substantially have the shape of an innersurface of a truncated cone, i.e. the membrane surface 242 is curved. Hence, the curvedmembrane surface 242, as illustrated in Figure 8A, is a species of a non-flat surface 242.ln effect, the transducer element 210 of figure 8A could have a shape as illustrated in e.g.Figure 7B.
Figure 8B is an illustration of the surface 242 of the membrane 240, shown in Figure 8A,when seen in the direction of arrow 420.
An embodiment of a process for the design of an audio reflector 400 may start by a stepS110 of establishing information describing the contour of the surface 242 of themembrane 240. This process, or parts of it, may be performed by means of a computer operating to execute a computer program.
The step S110 of establishing information describing the contour of the surface 242 mayinclude measuring the contour of the surface 242. Such measuring of the contour of thesurface 242 may include automatic measurement by means of optical scanner equipment,such as e.g. a laser scanner. Alternatively the measuring of the contour of the surface 242may include manual measurement of the surface 242, and/or a combination of automaticmeasurement and manual measurement. Based on the information established in stepS110, the contour of the surface 242 may be described as a number of points in a three-dimensional space. Hence, the surface 242 of the membrane 240 may be described by aplurality of points Ps, = (Xi, yi, zi). ln this context, please refer to Figure 8A which alsoillustrates a co-ordinate system having three axes representing three orthogonal dimensions x, y and z in three dimensional space. 21 ln a subsequent step, S120, a single first selected point 430 near the outer perimeter 270of the surface 242, or at the outer perimeter 270 of the surface 242, may be identified (seeFig 8A). ln this connection, a second point 450 is also identified. The second point 450may be a point at a distance DR from the first selected point 430 along a straight line (SeeFig 8D). According to an embodiment, the second point 450 may be a point on themembrane 240 near the outer perimeter 270 of the surface 242, or at the outer perimeter270 of the surface 242, when the membrane 240 is cone-shaped. When the membrane240 is cone-shaped having a substantially circular cone base, the distance DR may besubstantially twice the radius R1 of the base of the membrane 240. The membraneembodiment 240 illustrated in Figure 8D is cone-shaped, substantially as the membrane242 of Figures 7B, 7C and 7D, and hence the second point 450 may be a point on the farleft hand side of the cone base, as shown in Figure 8D, when the first selected point 430 is on the far right hand side of the cone base. ln a subsequent step, S130, the points describing the contour of the surface 242 may becopied so that a plurality of points PS2 = (XR, y',, zfi) represent a mirror surface 242'; themirror surface 242' as represented substantially being identical but mirror-inverted ascompared to the original surface 242 (see Fig 8C). This process may be performed bymeans of a computer operating to execute a computer program. The first selected point430 is mirrored by a first mirror point 430', and the second point 450 is mirrored by asecond mirror point 450”. With reference to Figures 8C and 8D, a line 460 may be drawnso as to connect the first mirror point 430' with the second mirror point 450”. ln actual fact, the line 460 may represent a back plane of the reflector-to-be. ln a subsequent step, S140, the points describing the contour of mirror surface 242' may,optionally, be moved by a certain amount Ay in the direction of the y-axis, as illustrated inFigure 8D. Hence, the moved mirror image, as shown in Fig 8D, may have a coordinatesPS2 = (xfi, y',, z',) = (Xi, yi+ Ay, zi). The certain amount Ay of movement in the direction of the y-axis may be set to zero. ln a step, S150, the points making up the mirror surface 242' are rotated by a certainangle oi around the first selected mirror point 430', as illustrated in Figure 8E, so thatsubstantially all points describing the contour of mirror surface 242'are moved in thedirection of the y-axis. ln this step, S150, only the selected point 430' may remain atsubstantially unchanged position, since all other coordinate points making up the mirror surface are rotated around it. According to an embodiment, this step may be performed 22 such that during the rotation of the mirror surface 242', the mirror surface is stretchedsuch that an arbitrary point PS'i = (x'i, y'i, z'i) of the mirror surface 242' will remain at an unchanged x-position while being moved in the y-direction.
Figure 8F is a sectioned lateral view of an embodiment of an audio generator 410 wherein the points PS'i = (XR, y'i, z'i) making up the mirror surface 242' have been rotatedby a certain angle oi around the selected mirror point 430'. ln the Figure 8F embodiment,the certain angle oi is about 45 degrees, and the certain amount Ay is zero, i.e. there has been no uniform translation in the y-direction.
With reference to Figure 8F, an embodiment of the audio generator 410 may comprise afirst aperture 315 which is defined by the plane of the base of the substantially coneshaped membrane 240. The first aperture 315 may be as discussed above in connectionwith figures 3 and/or 5 and/or 6 and /or Figure 8A. Hence, in Figure 8F the first aperture isillustrated by the line stretching from point 430 to point 450. The audio generator 410according to the Figure 8F embodiment also includes a second aperture 415. The plane416 of second aperture 415 is illustrated to stretch along a straight line connecting thepoint 450' and the point 450, in Figure 8F.
Sound generated by the membrane 240 may travel in the direction M, via the first aperture315, so as to be reflected by the surface 242' of the reflector 400. Sound reflected by thesurface 242' of the reflector 400 may thereafter leave the audio generator 410 via thesecond aperture 415 so as to travel in the direction of arrow 300' towards a plane P at adistance D3 from the plane 416 of second aperture 415. According to an embodiment, theplane P may coincide with the plane 416 of second aperture 415, when the distance D3 isvery short, or substantially zero. During a typical listening session, however, the plane Pwhere a user is likely to be positioned, may be at a distance D3 of more than one meter from the plane 416 of second aperture 415.
Figure 8G is another sectioned lateral view of the audio generator 410 of the Figure 8Fembodiment. With reference to Figure 8G, the geometry of embodiments of the audio generator 410 will be described.
According to embodiments of the invention, the geometry of the audio generator 410 issuch that a route R comprises two constituent distances: a first constituent distance R1 and a second constituent distance R2. The first constituent distance R1 is defined by a 23 straight line (parallel to arrow 300') being orthogonal to the plane 416 of second aperture415, and its value is the distance, along that straight line, from an arbitrary point on theplane 416 of second aperture 415 to a corresponding point PC on the non-flat surface 242'of the reflector 400 (See Fig 8G). The second constituent distance R2 is defined by asecond straight line (parallel to arrow M) being orthogonal to the plane 314 of firstaperture 315, and its value is the distance, along that second straight line, from the pointPC (referred to as “corresponding point”) on the non-flat surface 242' of the reflector 400 toa second corresponding point on the non-flat surface 242 of the membrane 240.According to some embodiments, the audio generator 410 is such that for any two suchroutes RA and RB it is true that the distance RA is substantially equal to the distance RB.Hence, the distance of the route RA is substantially equal to the distance of the route RB,both of which are substantially equal to a constant value C. Thus, the value of theconstant C may be determined by the geometry of the non-flat surface 242 of themembrane 240. According to an embodiment, the value of the constant C depends on thelongest distance, along a route R as described above, from a point on the plane 416 ofsecond aperture 415 to a corresponding point on the non-flat surface 242 of themembrane 240. When the non-flat surface 242 of the membrane 240 is substantially coneshaped, the value of the constant C may depend on the radius R1 of the membrane 240.Moreover, the value of the constant C may depend on the value of the certain amount Ayof movement, as selected in connection with step S140 of the design of the reflector, as described above.
According to some other embodiments, the audio generator 410 is such that for any tvvosuch routes RA and RB it is true that the distance RA is substantially equal to the distanceRB, except for routes originating or terminating substantially at the perimeter 270 of thefirst aperture 315. These descriptions of the geometry of the the audio generator 410, 390may be valid for a large range of angles q and for various sizes of the respective first andsecond apertures, and for various mutual relations of size between the first and second apertures.
The above described geometry of the audio generator 410 does not require the firstconstituent distance R1 and a second constituent distance R2 to be mutually orthogonal.However, according to some embodiments of the audio generator 410 the first constituentdistance R1 and a second constituent distance R2 are orthogonal to each other. With reference to Figure 8G, a number of first constituent distances R1 are illustrated as 24 distances Ax in the direction of an x axis, and a number of second constituent distancesR2 are illustrated as distances Ay.More particularly, a number of lines Ay1, Ay2, Ay3,... Ayi, Ay9 and Ay10 illustraterespective distances from the non-flat surface 242 of the membrane 240 to the non-flatsurface 242' of the reflector 400. A number of correspondingly referenced lines Ax1, Ax2,Ax3,... Axi, Ax9 and Ax10 illustrate the respective distances from the points of incidenceof the lines Ay1, Ay2, Ay3,... Ayi, Ay9 and Ay10 on the surface 242' to the plane 416 ofthe second aperture 415. According to embodiments of the invention the geometry of theaudio generator 410 is such that the sum Si of the distances xi and yi is constant: Si = Axi + Ayi = C, wherein C is a constant; and the index i is a positive integer, or zero.Whereas high quality of sound may be produced using a single audio generator 410 asdescribed above, it may sometimes be desired to provide p|ura| separate electro-audiotransducers for p|ura| frequency bands included in the drive signal 180. ln case two ormore separate electro-audio transducers are used in an audio generator 410, theseseparate electro-audio transducers should be arranged so as to maintain the above mentioned conditions A) and B), according to an embodiment of the invention. ln case two or more separate electro-audio transducers having non-flat surfaces, are used: The value of the above mentioned constant C may depend on the electro-audiotransducer having the largest membrane 240, or on the electro-audio transducer whose membrane 240 has the largest variation of surface non-flatness.
Figure 9 is a schematic side view of audio generator 410 comprising an example of p|ura|electro-audio transducers of mutually different geometrical constitution. There is a firstelectro-audio transducer 410| having a first large non-flat membrane 240|, a secondelectro-audio transducer 410.. having a non-flat membrane 240" which is smaller than thefirst large membrane 240| _ Finally, there is a third electro-audio transducer 410m having a flat membrane 240m.
An audio generator 410 having p|ura| electro-audio transducers , each adapted foroptimum reproduction of different frequency bands, may advantageously improve theperformance of the electro-audio transducer 410 in terms of correctly reproducing a wide spectrum of frequencies that may be included in the drive signal 180. ln this connection please refer to the discussion above (in connection with Fig. 5) aboutconditions for regenerating an acoustic signal 200 so that it truly represents the originalacoustic signal 110 (See Fig.1)with a minimum of distortion. ln particular, it is noted that the mutual temporal order of appearance, between any two siqnals havinq the different signal freguency in the original acoustic signal 110, must be maintained in the reproducedacoustic signal 200 (referred to as condition A2 above). When an original acoustic signal110 includes two separate signal component frequencies f1 and f2, e.g. one treble signalcomponent including a frequency f1 of 10 000 Hz and another signal component includinga frequency f2 of 50 Hz, a system for reproduction of acoustic signals may attempt toreproduce this multi-component acoustic signal 110, using separate transducer elements,such as a tweeter transducer element for reproducing the high frequency component f1 and a base transducer element for reproducing the low frequency component f2.
As mentioned above, the value of the above mentioned constant C may depend on theelectro-audio transducer having the largest membrane 240, or on the electro-audiotransducer whose membrane 240 has the largest variation of surface non-flatness, whentwo or more separate electro-audio transducers are used. Hence, with reference to Figure9, the inventor realized that in order for an audio generator 410, including plural electro-audio transducers 410., 410.., and 410..., to correctly transform an electrical signal to aseries of pressure waves (which may constitute an acoustic signal), the value of the abovementioned constant C is decided by the electro-audio transducer 410. having the largestmembrane 240, or on the electro-audio transducer whose membrane 240 has the largestvariation of surface non-flatness. ln the case illustrated in Figure 9, the decisive membrane is membrane 240. of the electro-audio transducer 410.. ln a typical commercial electro-audio transducer 410 there may be provided a bassmembrane 240., a midrange speaker membrane 240.. and a treble speaker membrane240.... ln such a commercial electro-audio transducer 410 the decisive membrane 240. willtypically be the membrane for producing the lowest audio signals, i.e. typically referred toas bass speaker membrane, or woofer membrane. Hence, in a typical installation themembrane 240. of the bass speaker or woofer will be the decisive membrane 240..Hence, a method for producing an audio generator 410 comprising plural electro-audiotransducers having membranes 240 of mutually different geometrical constitution may include the following steps: 26 S310: ln a first step: provide plural electro-audio transducers having membranes 240 ofmutually different geometrical constitution.
S320: Determine which one of the provided electro-audio transducers has the largestmembrane 240, or on the electro-audio transducer whose membrane 240 has the largestvariation of surface non-flatness. The selected electro-audio transducer will, in this text,be referred to as the decisive electro-audio transducer 410. having a decisive membrane240..
S330: Determine the value of the constant C, for the decisive membrane 240.. This maybe done as discussed above in connection with Figures 8A to 8G. The constant thusdetermined will, in this text, be referred to as the decisive constant C..
S340: Select one of the remaining electro-audio transducers 410.. from among the electro-audio transducers provided in step S310 having a non-flat membrane 240ll. The selectedelectro-audio transducer will now be referred to as electro-audio transducer 410.. having anon-flat membrane 240...
S350 Determine the value of the constant C.., for the selected electro-audio transducer410... This may also be done as discussed above in connection with Figures 8A to 8G.The constant thus determined will, in this text, be referred to as a dependent constant C..and the corresponding electro-audio transducer is referred to as the dependent electro-audio transducer 410... The value of the dependent constant C.. should be smaller than thevalue of the decisive constant C..
S360: Determine a difference value AC.-..: The difference value may be Åci-u = Ci ' Cu S370: When designing the audio generator 410 comprising plural electro-audiotransducers, the plane 416.. of the dependent electro-audio transducer 410.. should bepositioned at a larger distance from the plane P than the plane 416. of the decisiveelectro-audio transducer 410., the difference being the determined difference value AC.-...This is schematically illustrated in Figure 9. Hence, the difference value AC... may beexpressed as a distance, e.g. in millimeters.
S380: lf there is yet another electro-audio transducer provided in step S310 having a non-flat membrane 240ll: then repeat steps S340 to S370.
S390: Select one of the remaining electro-audio transducers 410., from among the electro-audio transducers provided in step S310, having a flat membrane 240.... The selectedelectro-audio transducer will now be referred to as flat membrane transducer 410.... Theflat membrane 240... of a flat membrane transducer 410... is such that S400: When designing the audio generator 410 comprising plural electro-audio transducers, the flat membrane 240... of a flat membrane transducer 410... should be 27 positioned at a position so that the distance C.-... of propagation from flat membrane 240...to the extended plane 416. of second aperture 415 of the decisive electro-audiotransducer 410. is substantially equal to the value of the decisive constant C. (See See Fig9 and/or Fig 11A). This may also be termed as follows: The flat membrane transducer410... has its second aperture 415 substantially at the plane of the flat membrane 240...,since the flat membrane 240... operates to generate a plane wave front. Hence, the constant C will have value zero (0) for the flat membrane transducer 410....
Figure 10A is an illustration of yet an embodiment of an audio generator 410 according tothe invention. The figure 10A embodiment includes the advantageous features of theaudio generator 190 described with reference to figures 2C and/or 2D with guiding walls510, 520, 530, 540 adapted so as to cause an increased sound propagation focus in thedirection 300A' towards the plane P at a distance D3 from the audio generator 410.However, the Figure 10 embodiment differs from the Figure 2A-2D embodiments in thatthe box structure 502 holds the enclosure 310, so that movement of the first membrane240A causes sound propagation in a first direction different to the direction 300', and theupper guide means 510 has been tilted so as to cause reflection of the sound exciting from first aperture 315.
Hence, with reference to Figure 10A, the audio generator 410 may comprise an aperture415, a reflector 560 and directive guiding walls 510, 520, 530, 540. The reflector 560 mayhave a surface adapted to reflect acoustic signals. The reflector co-operates with thedirective guiding walls so as to lead and guide said audio pressure waves to propagate inthe direction 300' so as to propagate in a direction orthogonal to the plane of the aperture415.
Figure 10B is a schematic cross-sectional view taken along line A-A of FIG 10A.
Hence, when movement of the membrane 240A causes a momentary increase in airpressure, i.e. a pressure pulse, having a direction of propagation vin the direction M,orthogonal to the plane of the first aperture plane 315, the pressure pulse is reflected inthe desired direction by reflector 560. The pressure pulses may also be maintained anddirected by the directive guiding walls 510, 520, 530 and 550 so as to focus the directionof movement of the pressure pulse in the direction 300A' towards a plane P at a distance from the audio generator 410. 28 Since a listener 205 will typically enjoy music at a distance D3 of more than one meter, orso, from the audio generator 410, it is advantageous to have the sound (which iscomposed of successive controlled pressure pulses) directed.
When a plane wave front of narrow width leaves a source, it will inherently spreadsideways in a manner that causes the resulting wave front to be curved at a large distancefrom the source. ln this connection, the directive guiding walls operate to lead and guide the successive pressure pulses as they propagate from the first aperture.
Figure 10B is a cross-sectional top view taken along line A-A of FIG 10A.
The sound waves exciting via the second aperture 415A. may propagate into thesurrounding space primarily in the direction 300A' which is orthogonal to the plane 416A|of the second aperture 415A.. However, the nature of sound waves is such that they mayspread somewhat also in other directions than the direction 300A'. According to anembodiment of the invention, the audio generator 410 may also include directive guidingwalls so as to cause an increased sound propagation focus in the direction 300A' which isorthogonal to the plane 416A| of the second aperture 415A|.
Hence, when movement of the membrane 240 causes a momentary increase in airpressure, i.e. a pressure pulse, having a direction of propagation vin the direction M,othogonal to the plane of the first aperture plane, the pressure pulse is maintained anddirected by the directive guiding walls so as to focus the direction of movement of thepressure pulse in the direction 300A' towards a plane P at a distance from the audio generator 410.
Since a listener 205 will typically enjoy music at a distance D3 of more than one meter, orso, from the audio generator 410, it is advantageous to have the sound (which iscomposed of successive controlled pressure pulses) directed.
When a plane wave front of narrow width leaves a source, it will inherently spreadsideways in a manner that causes the resulting wave front to be curved at a large distancefrom the source. ln this connection, the directive guiding walls operate to lead and guidethe successive pressure pulses as they propagate from the first aperture. Hence, the directive guiding walls, in the desired direction 300' whereas focused Figure 11A is an illustration of yet an embodiment of an audio generator 410 according tothe invention. The figure 10 embodiment combines the advantageous features of theaudio generator 190 described with reference to figures 10A and and 10B with the additional advantageous features of the audio generator 390, 410 described with 29 reference to figures 5-9. Accordingly, Figure 10B is also an illustration of a cross-sectional top view taken along line A-A of FIG 11A.
The Figure 11A audio generator 410 includes an enclosure 310 adapted to enclose aspace 320 between the first transducer element 210A and the second transducer element210B. According to an embodiment the enclosure 310 is a sealed enclosure. Hence, theenclosure 310 has a body 312 so that the body 312 cooperates with the membranes 240Aand 240B so as to prevent air from flowing freely between the air volume within the enclosure 310 and the ambient air.
The tvvo transducer elements 210A and 210B may advantageously be connected inreverse phase, as illustrated in Figure 2A and/or as illustrated in Figure 2B and as in Fig10. The Figure 11A audio generator 410 differs from the audio generator 190 of Figures2A and 2B in that it includes a first reflector 400A. The reflector 400A may be designed asdescribed above with reference to figures 5-9. Hence, Figure 11A audio generator 410may include a second aperture 415A, wherein the reflector 400A co-operates with the firsttransducer element 210A so that sound waves leaving the second aperture 415A in adirection 300A' orthogonal to the plane 416A. of the second aperture 415A are plane WGVGS.
Various embodiments and various parts of audio generators are disclosed below.An embodiment 1 of the invention comprises: a transducer element (210) having a membrane (240); and means (250) for causing the membrane (240) to move in dependence on aninput signal so as to cause audio waves to propagate in a direction (300, 300A, 300B) away from said membrane.
Embodiment 2. The transducer element (210) according to embodiment 1, whereinthe transducer element (210) includes a permanent magnet (260) which is firmly attachedto a transducer element body (280); and whereinthe membrane movement generator (250) includes a coil (250) adapted togenerate a magnetic field in response to reception of a drive signal.Embodiment 3. The transducer element (210) according to embodiment 1 or 2; whereinthe membrane (240) has an outer perimeter (270) which is flexibly attached to a portion (282) of the transducer element body (280).
Embodiment 4. The transducer element (210) according to any preceding embodiment;whereinThe drive signal (180) may be delivered via first drive terminals (252, 252A, 252B) and second drive terminals (254, 254A, 254B); the drive terminals being electricallyconnected to the coil (250) by first (256) and second (258) electrical conductors,respectively.
Embodiment 5. The transducer element (210) according to embodiment 4; wherein the first (256) and second (258) electrical conductors are adapted to allow the desiredmovement of the membrane (240) while allowing the first drive terminals (252, 252A,252B) and second drive terminals (254, 254A, 254B), respectively, to remain immobile inrelation to the transducer element body (280).
Embodiment 6. The transducer element (210) according to any preceding embodiment;wherein the transducer element body (280) is attachable to a baffle (230).
Embodiment 7. An audio generator (410, 190) comprising: a first transducer element (210A) being mounted such that the first transducer element(210A) can cause audio waves to propagate in a first direction (300A); a second transducer element (210B) being mounted such that the second transducerelement (210B) may cause audio waves to propagate in a second direction (300B) whichis different to the first direction (300A); an enclosure (310) adapted to enclose a space (320) between the first transducer element (210A) and the second transducer element (210B).
Embodiment 8. The audio generator (410, 190) according to embodiment 7; wherein the first transducer element (210A) and/or the second transducer element (210B) is/are asdefined in any of embodiments 1-6.
Embodiment 9. The audio generator (410, 190) according to embodiment 7 or 8; wherein the second direction (300B) is opposite to the first direction (300A).
Embodiment 10. An audio generator (410, 190) comprising:a membrane (240) having a surface (242) which is non-flat, anda reflector (400), whereinthe reflector (400) has a surface shape adapted to reflect audio waves propagating from the membrane surface such that a phase deviation, between two audio waves, 31 caused by said non-flat surface (242) is substantially eliminated at an arbitrary distance (D3) from the audio generator (410).Embodiment 11. An audio generator (410, 190) comprising: a transducer element (210)according to any preceding embodiment, wherein the membrane (240) has a surface (242) which is non-flat; the audio generator (410,190) further comprising: a reflector (400), wherein the reflector (400) has a surface shape adapted to reflect audio waves propagating from the membrane surface such that a phase deviation, between two audio waves, caused by said non-flat surface (242) is substantially eliminated at an arbitrary distance (D3) from the audio generator (410).Embodiment 12. The audio generator (410, 190) according to any preceding embodiment,further comprising: a baffle (230).Embodiment 13. The audio generator (410, 190) according to any preceding embodimentwhen dependent on embodiment 7; wherein the enc|osure (310) is a sea|ed enc|osure.Embodiment 14. The audio generator (410, 190) according to any preceding embodiment,wherein the tvvo transducer elements (210A, 210B) are connected in reverse phase.Embodiment 15. The audio generator (410, 190) according to any preceding embodiment,wherein the two transducer elements (210A, 210B) are connected in series.
Embodiment 16. The audio generator (410, 190) according to any preceding embodiment,whereinthe two transducer elements (210A, 210B) are connected in parallel.
Embodiment 17. The audio generator (410, 190) according to any preceding embodiment,wherein the two transducer elements (210A, 210B) are connected such that when the firstmembrane (240A) moves in the first direction (300A), then also second membrane (240B)moves in the first direction (300A).Embodiment 18. An audio generator (410) comprising: a membrane (240) having a surface (242) which is non-flat, a baffle (230); and a reflector (400), wherein the reflector (400) has a surface shape adapted to reflect audio waves propagating from the membrane surface such that a phase deviation, between two audio waves, caused by said non-flat surface (242) is substantially eliminated at an arbitrary distance (D3) from the audio generator (410). 32 Embodiment 19. The audio generator (410, 190) according to any preceding embodiment,further comprising a reflector (400), wherein the reflector (400) has a surface shape adapted to reflect audio waves (W1', W2')propagating from the membrane surface such that when said ref|ected audio waves (W1',W2') reach a plane (P) at a distance (D3) from the audio generator (410) said ref|ectedaudio waves (W1', W2') have trave|ed a substantially equal distance irrespective of fromwhich parts of the membrane surface the audio waves (W1', W2') originate.Embodiment 20. The audio generator (410, 190) according to any preceding embodiment,further comprising: a treble unit adapted to generate at least one treble audio wave.
Embodiment 21. The audio generator (410, 190) according to embodiment 20, wherein:said treble unit being adapted to generate said treble audio wave so thatsaid treble audio wave is in phase with said tvvo audio waves caused by said non-flat surface (242) at a distance (D3) from the audio generator (410).
Embodiment 22. The audio generator (410, 190) according to embodiment 20 or 21,wherein: said treble unit is positioned at certain distance behind said baffle.Embodiment 23. The audio generator (410, 190) according to any preceding embodiment,wherein said distance (D3) is a distance much larger than the surface deviation of said non-flat surface.

权利要求:
Claims (28)
[1] 1. Claims1. An audio generator (410, 190) comprising: a first transducer element (210A) being mounted such that the first transducer element(210A) can cause audio waves to propagate in a first direction (M); a second transducer element (210B) being mounted such that the second transducerelement (210B) may cause audio waves to propagate in a second direction which isdifferent to the first direction (M); an enc|osure (310) adapted to enc|ose a space (320) between the first transducerelement (210A) and the second transducer element (210B); wherein the first transducer element (210A) has a first membrane (240A) having a surface (242A) which is non-flat, and wherein the first membrane (240A) has an outer perimeter (270) which is flexiblyattached to a portion (282) of a transducer element body (280); said outer perimeter (270)defining a first aperture (315) having a first aperture plane (314) ; and wherein, inoperation, the first membrane (240A) is adapted to cause said audio pressure waves topropagate in the first direction (M, 300, 300A,) orthogonal to said first aperture plane(314); wherein said audio generator (410, 190) further comprisesa reflector (400), the reflector (400) havinq a surface (442) adapted to reflectacoustic signals; and directive guiding walls (510,520,530,540)the reflector (400) co-operatinq with the directive guiding walls so as to lead and guidesaid audio pressure waves to propagate in a second direction (300'); said seconddirection (300') being different from said first direction; and wherein the acoustically reflective surface (442) has a non-flat contour (242').
[2] 2. An audio generator (410, 190) comprising:a first transducer element (210) comprisinga membrane (240, 240A) having a surface (242, 242A) which isnon-flat,; andmeans (250) for causing the membrane (240) to move independence on an input signal so as to cause audio waves to propagate in afirst direction (M, 300, 300A, 300B) away from said membrane; and whereinthe membrane (240A) has an outer perimeter (270) which is flexibly attachedto a portion (282) of a transducer element body (280); said outer perimeter (270) defining a first aperture (315) having a first aperture plane (314) ; and wherein, in operation, the 34 membrane (240) is adapted to cause said audio pressure waves to propagate in the firstdirection (M, 300, 300A,) orthogonal to said first aperture plane (314); whereinsaid audio generator (410, 190) further comprisesa second aperture (415), a reflector (400) and directive guiding walls(510,520,530,540); the reflector (400) having a surface (442) adapted to reflectacoustic signals; and whereinthe reflector (400) co-operates with the directive guiding walls so as to lead and guide saidaudio pressure waves to propagate in a second direction (300') orthogonal to a plane ofsaid second aperture (415); said second direction (300') being different from said firstdirection; and wherein the acoustically reflective surface (442) has a non-flat contour (242').
[3] 3. The audio generator according to claim 1 or 2; wherein the non-flat contour (242') of the acoustically reflective surface (442, 242') isshaped such that a point (PC) on the surface (442, 242') is positioned at a first distance (DR1, Axi), along a first straight line in said second direction(300') orthogonal to the plane (416) of the second aperture (415), from the plane (416) ofsaid second aperture (415); and at a second distance (DR2, Ayi), along a second straight line orthogonal tothe plane (314) of the first aperture (315), from a corresponding point (Xi) on the non-flatsurface (242) of the membrane (240).
[4] 4. The audio generator according to claim 3; wherein the sum (Si) of the first distance (Dm, Axi) and the second distance (DRZ, Ayi)is a substantially constant value (C) for any a corresponding point (xi) on the non-flatsurface (242) of the membrane (240).
[5] 5. The audio generator according to claim 3 or 4; wherein said corresponding point (xi) on the non-flat surface (242) of the membrane(240) is a point on the surface (242) of the membrane (240) within the outer perimeter(270).
[6] 6. The audio generator according to claim 3 or 4; whereinsaid membrane has a substantially circular perimeter; said perimeter beingdescribable my means of a radius (R1) of said circular perimeter; and wherein the value of said constant (C) depends on said membrane perimeter radius (R1).
[7] 7. The audio generator according to any preceding claim, wherein said reflector (400) is arranged so that one part (430') of the reflector (400) ispositioned a large distance (Ax1) from said second aperture, and at a shorter distance(Ay1)from the non-flat surface (242) of the membrane (240); and another part (450') of the reflector (400) is positioned a shorter distance(Ax10) from the plane (416) of said second aperture (415) , and at a longer distance(Ay10) from the non-flat surface (242) of the membrane (240).
[8] 8. The audio generator according to any preceding c|aim when dependent on c|aim 3,whereinsaid first straight line in said second direction (300') is substantially orthogonal to the direction (M,) of the second straight line.
[9] 9. An audio generator (410, 190) comprising: a first membrane (240) having a surface (242) which is non-flat, anda reflector (400), wherein the reflector (400) has a surface (442) adapted to reflect acoustic signals;and wherein the acoustically reflective surface (442) has a non-flat contour (242')which has been defined in dependence on the contour of the non-flat surface(242) of the membrane (240).
[10] 10. The audio generator (410, 190) according to c|aim 9, whereinthe first membrane (240) has an outer perimeter (270) which is flexibly attached to a portion (282) of a transducer element body (280).
[11] 11. The audio generator (410, 190) according to c|aim 10, wherein said outer perimeter (270) defines a first aperture (315) having a firstaperture plane (314) ; and wherein, in operation, the membrane (240) is adapted to causesaid audio waves to propagate in a direction (M, 300, 300A,) orthogonal to said first aperture plane (314).
[12] 12. An audio generator (410, 190) comprising:a membrane (240) having a surface (242) which is non-flat, and a reflector (400), wherein 36 the reflector (400) has a surface shape adapted to reflect audio waves propagatingfrom the membrane surface such that a phase deviation, between two audio waves,caused by said non-flat surface (242) is substantially eliminated at an arbitrary distance (D3) from the audio generator (410).
[13] 13. The audio generator (410, 190) according to any preceding claim, whereinthe contour of the non-flat reflector surface (442) is adapted to compensatefor the non-flat surface (242) of the membrane (240) by substantially equalizing distances of propagation for mutually different rays of acoustic signals.
[14] 14. An audio generator (410, 190) comprising: a first transducer element (210A) being mounted such that the first transducer element(210A) can cause audio waves to propagate in a first direction (M); a second transducer element (210B) being mounted such that the second transducerelement (210B) may cause audio waves to propagate in a second direction which isdifferent to the first direction (M); an enclosure (310) adapted to enclose a space (320) between the first transducerelement (210A) and the second transducer element (210B); wherein the first transducer element (210A) has a first membrane (240A); and wherein the first membrane (240A) has an outer perimeter (270) which is flexiblyattached to a portion (282) of a transducer element body (280); said outer perimeter (270)defining a first aperture (315) having a first aperture plane (314); and wherein, inoperation, the membrane (240) is adapted to cause said audio pressure waves topropagate in said first direction (M, 300, 300A,) orthogonal to said first aperture plane(314); wherein said audio generator (410, 190) further comprisesdirective guiding walls (510,520,530,540) adapted to lead and guide said audio pressurewaves so as to focus the direction of propagation of the audio pressure waves in said first direction.
[15] 15. An audio generator (410, 190) comprising: a first transducer element (210A) being mounted such that the first transducer element(210A) can cause audio waves to propagate in a first direction (M); a second transducer element (210B) being mounted such that the second transducerelement (210B) may cause audio waves to propagate in a second direction which is different to the first direction (M); 37 an enclosure (310) adapted to enclose a space (320) between the first transducerelement (210A) and the second transducer element (210B); whereinthe first transducer element (210A) has a first membrane (240A); and whereinthe first membrane (240A) has an outer perimeter (270) which is flexiblyattached to a portion (282) of a transducer element body (280); said outer perimeter (270)defining a first aperture (315) having a first aperture plane (314); and wherein, inoperation, the membrane (240) is adapted to cause said audio pressure waves topropagate in said first direction (M, 300, 300A,) orthogonal to said first aperture plane(314); whereinsaid audio generator (410, 190) further comprisesa second aperture (415), a reflector and directive guiding walls(510,520,530,540); the reflector having a surface adapted to reflect acoustic signals;and whereinthe reflector co-operates with the directive guiding walls so as to lead and guide saidaudio pressure waves to propagate in a second direction (300') so as to propagate in adirection orthogonal to the plane of said second aperture (415); said second direction (300') being different from said first direction.
[16] 16. The audio generator according to claim 15, wherein the first membrane (240A) has a surface (242A) which is non-flat, andwherein the reflector surface (442) is non-flat; the contour of the non-flat reflectorsurface (442) being adapted to compensate for the non-flat surface (242) of themembrane (240) by substantially equalizing distances of travel for mutually different rays of acoustic signals.
[17] 17. The audio generator according to claim 2 or 16; wherein the non-flat contour (242') of the acoustically reflective surface (442, 242') isshaped such that a point (PC) on the surface (442, 242') is positioned at a first distance (DR1, Axi), along a first straight line in said second direction(300') orthogonal to the plane (416) of the second aperture (415), from the plane (416) ofsaid second aperture (415); and at a second distance (DR2, Ayi), along a second straight line orthogonal tothe plane (314) of the first aperture (315), from a corresponding point (Xi) on the non-flatsurface (242) of the membrane (240). 38
[18] 18. The audio generator according to claim 17; wherein the sum (SH) of the first distance (DRH, AxH) and the second distance (DRZ, AyH)is a substantially constant value (C) for any a corresponding point (xH) on the non-flatsurface (242) of the membrane (240).
[19] 19. An electro-audio transducer comprising at least a first and a second audio generatoraccording to any preceding claim when including claim 2 or 16; wherein the first audio generator (410H) has a larger membrane than the secondaudio generator (410H), and the first audio generator (410H) has a decisive secondaperture (415H); and the second audio generator (410H) has a dependent second aperture (415H) ;and the plane (416H) of the dependent second aperture (415H) iS positioned inrelation to the plane (416H) of the decisive second aperture (415H) so that the plane (416H)of the dependent second aperture (415H) is substantially parallel to the plane (416H) of thedecisive second aperture (415H), and the plane (416H) of the dependent second aperture (415H) iS displaced inrelation to the plane (416H) of the decisive second aperture (415H).
[20] 20. The electro-audio transducer according to claim 19, wherein the distance of displacement (ACHH, ACHHH) depends on a relation between the membranes of the first and a second audio generator.
[21] 21. The electro-audio transducer according to claim 19 when dependent on claim 18,wherein the first audio generator (410H) has a decisive sum value (SH, CH), and the second audio generator (410H) has a dependent sum value (SHH, CH); andwherein the distance of displacement (ACHH, ACHHH) depends on a relation or adifference between said decisive sum value (SH, CH) and said dependent sum value (SHH,CH).
[22] 22. The electro-audio transducer according to any of claims 1 or 14 or 15; wherein said enclosure comprises means for air pressure equalization.
[23] 23. A method for designing a reflector for use in an audio generator (410H) having a membrane (240) with a first non-flat surface (242); the method comprising 39 establishing (S110) information describing a contour of a first non-flatsurface (242); generating (S130) a plurality of points (PS',; x',, y',, z',) so as to represent areversed version (242') of said first non-flat surface (242) in three-dimensional space; saidplurality of points (PS',; x',, y',, z',) being generated in dependence on said establishedinformation; rotating (S150) said plurality of points (PS',; xfi, y',, z',), by a certain angle (d) around a selected point of rotation (430').
[24] 24. The method according to claim 23; wherein said rotation step is performed such that the representation of said reversednon-flat version surface (242') is stretched such that an arbitrary point PS2 = (x',, y',, z',) ofthe reversed non-flat version surface (242') remains at a substantially unchanged positionin at least one first dimension (x) while being moved in a second dimension (y), said second dimension being orthogonal to said first dimension.
[25] 25. A method according to claim 23 or 24, wherein,said information establishing step (S110) includes use of an optical scanner so as to establish measurement data describing a contour of a first non-flat surface (242).
[26] 26. A method according to claim 23, 24 or 25, further comprising: storing position values representing the position of said contour of said firstnon-flat surface (242), and storing position values representing the position of saidreversed non-flat version surface (242'); or storing information indicative of a relative positioning of said contour of said first non-flat surface (242) and said reversed non-flat version surface (242').
[27] 27. A method according to any of claims 23 - 25, further comprising:storing said representation of said reversed non-flat version surface (242') as a templet for an audio signal reflector.
[28] 28. A method for producing a reflector for use in an audio generator (410|) having amembrane (240) with a first non-flat surface (242); the method comprising:using an audio signal reflector templet as a model for the manufacture of an audio reflector.

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法律状态:

优先权:

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申请号 | 申请日 | 专利标题

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SE1150707|2011-07-15|

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SE1250809A|SE536652C2|2011-07-15|2012-07-10|An acoustic signal generator|SE1250809A| SE536652C2|2011-07-15|2012-07-10|An acoustic signal generator|