• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The headset includes active noise control, with an internal ANC microphone (28) placed inside the acoustic cavity (22) and delivering a signal having an acoustic noise component. A digital DSP signal processor (50) comprises a feedback ANC branch (54) applying a filter transfer function (54, HFB2) to the signal delivered by the microphone ANC, and signal mixing means (46) of the branch feedback with an audio signal to be reproduced (M). The headset includes a motion sensor (64) mounted on one of the headphones. The DSP includes means (68) for concurrently analyzing i) the signal delivered by the internal microphone (28) and ii) the signal delivered by the motion sensor (64), and to check whether current characteristics of these signals verify or not a battery of predetermined criteria. Upstream of the feedback ANC filter (54), an anti-saturation filter (70, HFB1) is selectively switched according to the result of this check. The filtering of an equalization branch (58, HEQ2) of the signal to be reproduced (M) is also modified by a similar anti-saturation filter (72, HEQ1).
    公开号:FR3021180A1
    申请号:FR1454406
    申请日:2014-05-16
    公开日:2015-11-20
    发明作者:Co Thuy Vu Hoang；Benoit Pochon；Phong Hua；Pierre Guiu
    申请人:Parrot SA；
    IPC主号:
    专利说明:

    [0001] The present invention relates to an audio headset comprising an "active noise control" system. Such headphones can be used for listening to an audio source (eg music) from a device such as an MP3 player, radio, smartphone, etc. to which it is connected by a wired connection or by a wireless link, in particular a connection of the Bluet ooth type (registered trademark of the Bluetooth SIC). If it is equipped with a microphone unit capable of picking up the voice of the wearer of the headset, it is also possible to use this headset for communication functions such as "hands-free" telephony functions, in addition to the listen to the audio source. The headset transducer then reproduces the voice of the remote speaker with which the wearer of the headset is in conversation. The headset usually includes two headphones joined by a hoop.
    [0002] Each earpiece comprises a closed shell housing a sound reproduction transducer (hereinafter simply referred to as a "transducer") and intended to be applied around the user's ear with the interposition of a circumaural pad isolating the ear of the ear. external sound environment.
    [0003] There are also earpieces of the type called "intra-auricular" with an element to be placed in the ear canal, thus having no cushion surrounding or covering the ear. In the following, reference will mainly be made to headphones of the "headphone" type with a transducer housed in a shell surrounding the ear ("circum-aural" headphones) or in support of it (headphones "supra-aurai"). "), but this example should not be considered as limiting, the invention being able to be applied, as will be understood, to intra-ear headphones. When the headset is used in a noisy environment (metro, street, train, airplane, etc.) the wearer is partially protected from noise by the headphones headphones, which isolate it with the closed shell and the circumaural pad. However, this purely passive protection is only partial, a part of the sounds, especially in the lower part of the frequency spectrum, which can be transmitted to the ear through the shell of the earphones, or via the cranial box of the wearer.
    [0004] It is for this reason that techniques have been developed called "active noise control" or ANC (Active Noise Control), the principle of which is to capture the incident noise component and superpose, temporally and spatially, this noise component an acoustic wave which is ideally the inverted copy of the pressure wave of the noise component. This is to create in this manner a destructive interference with the noise component and reduce, ideally neutralize, the pressure variations of the parasitic acoustic wave. EP 2 597 889 A1 (Parrot) describes such a headset, equipped with an ANC system combining feedback-type, closed-loop, and feedforward, open-loop filtering. The feedback filtering channel is based on a signal collected by a microphone placed inside the acoustic cavity delimited by the shell of the earphone, the circumaural pad and the transducer. In other words, this microphone is disposed near the ear of the user, and mainly receives the signal produced by the transducer and the residual noise signal, unneutralized, still noticeable in the front cavity. The signal from this microphone, from which the audio signal of the music source to be reproduced by the transducer is subtracted, constitutes an error signal for the feedback loop of the ANC system. The feedforward filtering channel uses the signal picked up by the external microphone to collect the spurious noise in the helmet wearer's immediate environment. Finally, a third filtering channel processes the audio signal from the music source to be reproduced. The output signals of the three filter channels are combined and applied to the transducer to reproduce the signal of the music source associated with a surrounding noise canceling signal. The VVO 2010/129219 A1 (EP 2 425421 AO) describes another ANC system, of adaptive type, that is to say using filters whose transfer function is dynamically modified, continuously, by an analysis algorithm. in real time signal. An external microphone placed on the shell of the earphones of the headset collects ambient noise, the level of which is analyzed to adjust the transfer function of the feedback filter to adapt to the noise prevailing in the external environment of the headphones. Existing ANC systems are subject to a phenomenon that occurs when the internal acoustic cavity of the earpiece undergoes sudden, inaudible but excessive decompression and decompression, the amplitude of which is so great that the microphone diaphragm crashes sharply and produces an electrical signal exceeding its nominal limit. This phenomenon occurs in particular when handling the helmet, or when the user is walking heavily or short. The movements of the helmet then create excessive overpressures and depressions in the front cavity, which results in a strong electrical peak in the low frequencies. The excessive signal picked up by the microphone creates in the ANC feedback filter a saturation leading to an audible signal or "plop" produced at the output by the transducer and unpleasant for the user. This phenomenon can even occur under normal walking conditions, where pitch noise resonances in low frequencies below 100 Hz are heard and sometimes annoying. The feedback ANC filter can attenuate these pitch noise resonances by amplifying the internal microphone signal but, when the steps become stronger, the electrical level of the microphone signal can exceed the limits of its normal operation and cause, here again, a saturation ANC filter and transducer. This saturation can occur at several points in the signal processing chain: electrical overshoot of the input dynamics of the analog / digital converter, exceeding of the maximum digital value in the digital signal processor DSP, or output saturation. if the signal reproduced by the transducer exceeds the maximum value that can be produced by the digital / analog converter, each of these phenomena can cause a "plop" unpleasant. The object of the invention is to propose a new ANC noise reduction technique making it possible to overcome these phenomena by: - compensating for pneumatic overpressure / pressure phenomena in the acoustic cavity of the earpiece, in particular because of the movements of not the user of the helmet; - without degradation of ANC noise-canceling performance, that is to say that the residual noise perceived by the user will always be reduced at best, especially with i) a strong attenuation of the low frequencies and ii) a large bandwidth suppression frequency; - all, without the audio signal from the music source (or the voice of the remote speaker, in a telephony application) being distorted, and without the spectrum of this signal is reduced by the ANC processing - although the noise canceling signal and the audio signal to be reproduced are amplified by the same channel and reproduced by the same transducer. Another object of the invention is to implement a digital technology (and not analog as in the EP 2,597,889 A1 cited above) for such an ANC system, particularly implementable within a digital signal processor (DSP). To achieve these goals, the invention provides an audio headset as disclosed by the VVO 2010/129219 Al supra, with an ANC active noise control system. Such a headset comprises two earphones each with a sound reproduction transducer of an audio signal to be reproduced, this transducer being housed in an acoustic ear cavity. The ANC active noise control system comprises an ANC microphone adapted to deliver a captured signal comprising an acoustic noise component, and a digital signal processor DSP. The DSP comprises a closed-loop feedback branch comprising an ANC feedback filter capable of applying a filter transfer function to the signal delivered by the ANC microphone, and mixing means receiving as input the signal delivered by the output feedback branch. ANC filter feedback and an audio signal to reproduce and outputting a signal capable of driving the transducer.
    [0005] In a characteristic manner of the invention, the microphone ANC is an internal microphone placed inside the acoustic cavity, and the headset further comprises a motion sensor mounted on at least one of the headphones and capable of delivering an accelerometric signal. The DSP further comprises means for preventing effects on the feedback branch of a saturation of the signal delivered by the internal microphone, these means comprising: means capable of analyzing concurrently i) the microphone signal delivered by the internal microphone and ii) the accelerometer signal delivered by the motion sensor, and checking whether current characteristics of these microphonic and accelerometric signals verify or not a first set of predetermined criteria; and, in the feedback branch upstream of the feedback filter ANC, a selectively switchable feedback antisattering filter according to the result of the verification of the first set of criteria. According to various advantageous subsidiary characteristics: the feedback saturation filter is one of a plurality of selectively switchable preconfigurable filters, and the DSP further comprises means capable of selecting one of the preconfigured anti-saturation filters in function the result of the verification of the first set of criteria; the DSP further comprises: an equalization branch, comprising an equalization filter able to apply an equalization transfer function to the audio signal to be reproduced before it is applied to the mixing means; and, in the equalization branch upstream of the equalization filter, a selectively mutable anti-saturation filter at the same time as the feedback saturation filter; the equalization anti-saturation filter is one of a plurality of selectively switchable preconfigurable equalization filters, and the DSP further comprises means capable of selecting one of the preconfigured equalization filters as a function of the result of the verification of the first set of criteria; the current characteristics of the accelerometric signal comprise an energy value of the accelerometric signal, and the predetermined criteria comprise a threshold at which said energy value is compared. These may include energy values in a plurality of respective frequency bands, the predetermined criteria comprising a series of respective thresholds at which these energy values are compared if the energy value of the accelerometer signal exceeds the threshold; the feedback filter ANC is one of a plurality of preconfigured, selectively switchable ANC filters, and the DSP further comprises: means for analyzing the signal delivered by the internal microphone, able to verify whether current characteristics of the signal delivered by the internal microphone or not verify a second set of predetermined criteria; and selection means, adapted to select one of the preconfigured feedback ANC filters according to the result of the verification of the second set of criteria; the DSP further comprises an equalization branch, comprising an equalization filter able to apply an equalization transfer function to the audio signal to be reproduced before it is applied to the mixing means. The equalization filter is one of a plurality of preconfigured, selectively switchable equalization filters, and the selection means are also able to select one of the preconfigured equalization filters, depending on the ANC filter feedback current selected. An embodiment of the invention will now be described with reference to the appended drawings in which the same references designate elements that are identical or functionally similar from one figure to another. Figure 1 generally illustrates an audio headset resting on the head of a user. Figure 2 is a schematic representation showing the various acoustic and electrical signals as well as the various functional blocks involved in the operation of an active noise control headphones. Figure 3 is an elevational section of one of the earphones of the helmet according to the invention, showing the configuration of the various mechanical elements and electromechanical members thereof.
    [0006] FIG. 4 illustrates an example of a typical waveform of the electrical signal delivered before amplification by the internal microphone of an ANC helmet, in two jumps by the helmet wearer. Figure 5 schematically illustrates, in the form of functional blocks, the manner in which the denoising treatment according to the invention is carried out. FIG. 6 illustrates more precisely the elements implementing the function of analyzing the microphone signal and selecting the filters to be applied to the signals to be delivered to the headphone transducer. Figure 7 is a flowchart describing the operation of the state machine of the analysis and selection function of Figure 6.
    [0007] FIG. 8 represents, in amplitude and in phase, the transfer functions of the ANC filter with and without the anti-saturation filtering according to the invention, selected automatically according to the movements detected. FIG. 9 illustrates attenuation examples obtained in the two cases exemplified in FIG. 8. FIG. 1 shows an audio headset placed on the head of its user. This headset comprises, in a conventional manner, two earphones 10, 10 'joined by a holding bar 12. Each of the earphones 10 comprises an outer shell 14 which is applied to the contour of the ear of the user. , with interposition between the shell 14 and the periphery of the ear of a flexible circumaural pad 16 for providing a sound seal, acoustically, between the region of the ear and the external sound environment. As indicated in the introduction, this example configuration of "headphone" type with a transducer housed in a shell surrounding the ear or resting on it should not be considered as limiting, the invention can also be well applied to earphones in-ear including an element to place in the ear canal, so headphones without shell and cushion surrounding or covering the ear. Figure 2 is a schematic representation showing the various acoustic and electrical signals as well as the various functional blocks involved in the operation of an active noise control headphones. The earphone 10 encloses a sound reproduction transducer 18, hereinafter referred to simply as a "transducer", carried by a partition 20 defining two cavities, namely a front cavity 22 on the side of the ear and a rear cavity 24 on the opposite side. . The front cavity 22 is defined by the inner partition 20, the wall 14 of the earpiece, the pad 16 and the outer face of the user's head in the region of the ear. This cavity is a closed cavity, with the exception of the inevitable acoustic leaks in the region of contact of the pad 16.
    [0008] The rear cavity 24 is a closed cavity, with the exception of an acoustic vent 26 for obtaining low frequency enhancement in the front cavity 22 of the earpiece. Finally, for active noise control, there is provided an internal microphone 28 arranged as close as possible to the auditory canal of the ear, in order to capture the residual noise present in the internal cavity 22, which noise will be perceived by the user. - By ignoring the audio signal of the music source reproduced by the transducer (or the voice of the remote speaker, in a telephony application), the acoustic signal picked up by this internal microphone 28 is a combination of: - the residual noise 32 coming from the transmitting the surrounding external noise 30 through the shell 14 of the earpiece, and - a sound wave 34 generated by the transducer 18, which is, ideally according to the principle of destructive interference, the inverted copy of the residual noise 32, that is to say the noise to be deleted at the point of listening. The neutralization of the noise by the sound wave 34 is never perfect, the internal microphone 28 collects a residual signal which is used as an error signal e applied to a feedback filter branch 36 closed loop. Optionally, an external microphone 38 may be placed on the shell of the earphones of the headset, to capture the surrounding noise outside the earpiece, schematized by the wave 30. The signal collected by this external microphone 38 is applied to a feedforward 40 filter stage of the active noise control system. The signals coming from the feedback branch 36 and, if present, from the feedforward branch 40 are combined at 42 to drive the transducer 18. In addition, the transducer 18 receives an audio signal to be reproduced from a musical source (player , radio, etc.), or the voice of the remote speaker, in a telephony application. Since this signal experiences the effects of the closed loop distorting it, it will have to be preprocessed by an equalization so as to present the desired transfer function, determined by the gain of the open loop and the target response without active control. The helmet may optionally carry, as shown in Figure 1, another external microphone 44 for communication functions, for example if the headset is provided with "hands-free" telephony functions.
    [0009] This additional external microphone 44 is intended to pick up the voice of the wearer of the helmet, it does not intervene in the active control of the noise and, in the following, it will be considered as an external microphone possibly used by the ANC system that the microphone 38 dedicated active noise control. Figure 3 illustrates, in section, an embodiment of the various mechanical and electroacoustic elements shown schematically in Figure 2 for one of the earphones 10 (the other earpiece 10 'being made identically). It contains the partition 20 dividing the inside of the shell 14 into a front cavity 22 and a rear cavity 24 with, mounted on this partition, the transducer 18 and the internal microphone 28 carried by a gate 48 maintaining it nearby. of the ear canal of the user. The object of the invention is to overcome the phenomenon, explained in the introduction, resulting from the sudden surges / depressions in the front cavity 22 which are likely to produce, especially in the low frequencies below 100 Hz, extreme overruns in the value of the signal delivered by the internal microphone 28. Thus, FIG. 4 illustrates an example of a signal delivered by the internal microphone 28, in this case an electret microphone which delivers a signal not exceeding 100 mV for a sound pressure of 110 dB SPL (Sound Pressure Level). However, as illustrated in FIG. 4, in the case of two small successive jumps, it is found that this value can be very largely exceeded (in the example, it reaches and exceeds 600 mV), which can produce, after amplification, saturation effects. in several places in the processing chain. The basic idea of the invention is to detect upstream of the feedback filter, with a very low latency time, the situations likely to produce such signal peaks, in order to avoid all saturation phenomena during sudden movements. helmet, especially while the user is walking or running. FIG. 5 schematically illustrates, in the form of functional blocks, the ANC active noise control system incorporating, according to the invention, an anti-saturation function making it possible to compensate for this phenomenon.
    [0010] It is a digital type ANC system implemented by a DSP digital signal processor 50. It will be noted that, although these diagrams are presented in the form of interconnected circuits, the implementation of the various functions is essentially software, this representation being only illustrative. We find the feedback branch whose principle was described above with reference to Figure 2, after scanning by means of an ADC converter 52 of the error signal e picked up by the internal microphone 28. The digitized error signal is it is processed by a feedback filter 54, then converted into an analogue by the DAC 56 in order to be reproduced by the transducer 18 in the cavity of the receiver 10. The reproduced signal is optionally combined with a music signal M which, after equalization at 58, is combined at 60 with the noise cancellation signal for conversion by the DAC 56 and reproduction by the transducer 18.
    [0011] The filtering performed by the blocks 54 (HFB2 feedback transfer function on the microphone signal) and 58 (music equalization transfer function 11E02 of the music M) can be performed in particular in the manner described in the application FR 14 53284 of 11.04. 2014, in the name of the Applicant, entitled "Active noise control ANC noise headphones with electric breath reduction", which proposes to implement a plurality of predetermined filter configurations, selectively switchable according to the signal picked up by the internal microphone 28, so as to optimize the compromise between the more or less attenuation of the ambient noise and that of a more or less strong electric wind, depending on the level and the spectral content of the signal returned to the user, as collected by the microphone 28 placed in the front cavity 22 of the earpiece. This particular technique of anti-blast filtering is however in no way limiting, and the anti-saturation system according to the invention is equally applicable to feedback and equalization filtering operated by other techniques. In the illustrated example, the active noise control ANC is controlled by an ANC module 62 which analyzes the signal e and adapts accordingly the FIFE32 transfer functions of the feedback branch 54 and HEQ2 of the equalization branch 58 of the music signal. More specifically, the signal e picked up by the internal microphone 28 (which is assumed to be identical to the signal picked up by the ear of the headphone user) is (in the configuration of FIG. 5). ) given by: e = H ', 1 (1-Ha * HFB2) * B + Ha / (1-Ha * HFB2) * HE02 * MB being the external noise signal 30, M being the incoming music signal, H 'being the transfer function between an external noise source and the internal microphone 28, HFB2 being the transfer function of the feedback filter 54, HE02 being the transfer function of the equalizing filter 58, and H being the transfer function between the transducer 18 and the internal microphone 28. From this equation, it can be seen that a played music signal is subjected to a transfer function: Ha / (1-Ha * HFB 2) * HEo 2 20 so that if the HFB2 filter ANC branch feedback 54 is changed, the perception of music by the user is also changed. In order for the perception of the music to remain the same, the control algorithm ANC 62 modifies the HE-02 filter of the music equalization branch 58 at the same time as that of the ANC feedback branch 54 to re-balance the effects. filtering, of course if a music signal is present. In a manner characteristic of the invention, together with the signal of the internal microphone 28, the ANC active noise control processing uses an accelerometer 64 mounted on the helmet (FIGS. 2 and 5), the role of which will be to detect with a very low latency movements of the earphone likely to produce saturation effects of the signal picked up by the internal microphone 28, typically movements resulting from the movements of the user while it is running, running, jumping ... or again when he manipulates the headphones, for example to readjust their position on his ears. 3 02 1 1 80 12 EP 2 518 724 A1 (Parrot) describes a helmet comprising an accelerometer integrated into an earphone, but in this document the accelerometer is used as a physiological sensor to collect non-acoustic vocal components transmitted by bone conduction, therefore not noise, a speech signal emitted by the user, for example in the case where the headset is used as a "hands-free" device in combination with a mobile phone. In the case of the present invention, this same accelerometer can be used, but with a different role, namely the improvement of the ANC function of the headphones, in a configuration of listening (sound reproduction) and not of speech (voice of the user). The signal of the accelerometer 64, after scanning by means of an ADC converter 66, is applied to an "anti-saturation" module 68 which also receives the signal e collected by the internal microphone 28, after scanning by the ADC converter 52 The two acceleration and microphonic signals are analyzed jointly by the anti-saturation module 68, which controls a filter 70 (HFB / transfer function) placed in the feedback branch upstream of the actual feedback filtering ( block 54, transfer function HFB2), and likewise an equalization filter 72 (transfer function HEM placed in the equalization branch upstream of the equalization filter (block 58, transfer function HE02). , but in a nonlimiting manner, it is possible to provide, for the blocks 70 and 72 respectively defining the transfer functions of the feedback and equalization branches, a plurality of predefined filtering configurations. selectively switchable, with an intelligent rocking mechanism between these different filters based on the signals picked up jointly by the accelerometer 64 and the internal microphone 28. The anti-saturation module 68, from these signals, defines that of the X 30 filters of the block 70 of the feedback branch that should be selected and, likewise, that of the Y filters of the block 72 of the equalization branch of the music signal that should be selected (Y can be equal to X, but not necessarily).
    [0012] The selection between the X filters of the transfer function IIFBI of the block 70 (or Y filters of the transfer function HEol of the block 72) is done as follows. For each of the filters, one interpolates its parameters (central frequency fo, quality factor Q and gain G) and during a transition the coefficients are calculated with respect to these interpolated parameters between the initial state and the final state. Typically, it is possible to use an infinite impulse response (IIR) filter, ie a type of filter characterized by a response based on the values of the input signal as well as the previous values of the answer that this filter could have produced. It is possible to use in particular an IIR filter of order 2, called "biquad" whose transfer function gives the output signal y at time n as a function of the input signal x at times n, n-1 and n- 2 is given by: Y (n) = bex (n) + bi * x (n-1) + b2 *, c (n-2) - ai * y (n-1) - a2 * y (n-2) ), the coefficients al, a2, 1.0, blet b2 of the transfer function being derived from the parameters fo, Q and G of the filter. Figure 6 illustrates more precisely the elements implemented by the anti-saturation module 68 for the analysis of the signal and the selection of the filters of the blocks 70 and 72. The digitized signal e collected by the internal microphone 28 is subjected to a decomposition frequency by a battery of filters 74 in order to calculate at 76 the energy Rms, of this signal e in each of its N frequency components. For example, Rmsi may be the power of the microphone signal below 100 Hz, Rms2 the signal power around 800 Hz, etc. which allows via the spectral analysis to distinguish various significant situations: for example, for use of the headset in a noisy transport-type environment (aircraft, train), the ratio between low and high frequencies is much greater than in an envi - quieter environment such as in an office. The obtained values Rmsj, Rrns2 Rms are applied to a state machine 78, which compares these energy values with respective thresholds and determines, based on these comparisons, that of the X filters of the block 70 of the feedback branch and the case appropriate (if music is present) that of the Y filters of block 72 of the equalization branch to be selected. Figure 7 illustrates more precisely the manner in which this state machine 78 operates.
    [0013] The RMS power of the signal of the accelerometer present on the helmet is, possibly after pre-filtering, analyzed continuously. If this power exceeds a predetermined threshold Threshold a (test 80) then the state machine considers that the headset undergoes a movement that may result in saturation of the ANC control and triggers an anti-saturation control process, corresponding to the left side of the algorithm in Figure 7. On this algorithm, the Activity and Attenuation parameters are Boolean variables, while the Timeri and Timer2 parameters are count values of a timer that is reset by an action " Timer = 0 ", the notation" Timer ++ "indicates that the algorithm allows the timer to continue. In the presence of an acceleration exceeding the prescribed threshold, the state machine analyzes the signal of the internal microphone 28. If the power RMS / (power of the microphonic signal in a certain frequency range) exceeds a predetermined threshold Threshold ( test 82), then the state machine modifies the transfer function HFB1 of the feedback branch, for example by selecting one of the X filters which has the effect of reducing the attenuation ANC in the low frequencies, and also modifies the HE01 transfer function of the equalizer branch to keep the same perception of the music (block 84). In the opposite case, the power RMS2 of the microphonic signal in another frequency band is tested in the same way (block 82 ') with respect to a second threshold Threshold 2 (with Threshold _2 <Threshold I). If RMS2> Threshold 2, then a modification of the Hpgi and Hall transfer functions (block 84 ') is also applied, typically with an attenuation of the feedback ANC present, but less important than in the previous case. It is thus possible to test a number of successive thresholds (82 "test) iteratively with progressively lower thresholds, so as to choose, among the X selectable filters of the feedback branch HFB1, the one that will optimize the compromise between the attenuation. the ANC control and the protection against saturation of it (block 84 "). If in all the bands the signal strength of the internal microphone 28 is lower than the lowest threshold, it is considered that there is no risk of saturation and, after expiry of a time delay of X2 seconds (test 86) the state machine disables the anti-saturation modules 70 and 72 (block 88). Assuming that, in test 80, the signal analysis of the accelerometer indicates that it does not exceed the prescribed threshold, if the anti-saturation treatment was active (test 90), then at the expiration of a timer of X / seconds (test 92), this control is automatically deactivated by the state machine (block 94). Turning off the saturation control and "waking it up" only at the right time offers the advantage of a significant saving on the power consumption of the DSP 50, thus increasing the autonomy of the headphones. FIGS. 8 and 9 illustrate two examples of HFBI transfer functions applied to the feedback branch of the ANC control, without (A) and with (B) modification by the anti-saturation module 68: FIG. 8 represents, in amplitude and in phase , the transfer function HFBi in these two cases, while Figure 9 illustrates the corresponding attenuations obtained. It is found that the detection of an acceleration triggers an attenuation of the gain of the feedback ANC branch of the order of 12 to 15 dB at 40 Hz between the curve A (without anti-saturation control) and the curve B (with anti-control -saturation). The change is mainly made in the low frequencies, below 150 Hz, because it is in this range of frequencies that the resonances of footsteps, etc. are located. usually encountered in practice. The anti-saturation control decreases, certainly, the attenuation performance of the ANC control but, in return, avoids the production of a very unpleasant "plop" output by the transducer due to the saturation of the control branch ANC feedback.
    权利要求:
    Claims (8)
    [0001]
    REVENDICATIONS1. An audio headset, comprising two earphones (10) each comprising a transducer (18) for reproducing sound of an audio signal to be reproduced, this transducer being housed in an acoustic ear cavity (22), this headset comprising a control system noise asset, ANC, with: an ANC microphone, able to deliver a sensed signal comprising an acoustic noise component; a digital signal processor, DSP, (50) comprising: a closed loop feedback branch (36), comprising a feedback ANC filter (54) adapted to apply a filter transfer function (HFB) to the signal delivered by the ANC microphone; and mixing means (46), receiving as input the signal delivered by the feedback branch at the output of the feedback filter ANC (54) and an audio signal to be reproduced (S), and outputting a signal capable of driving the transducer (18), characterized in that: - the microphone ANC is an internal microphone (28) placed inside the acoustic cavity (22); the helmet furthermore comprises a movement sensor (64) mounted on at least one of the earphones and capable of delivering an accelerometric signal; the DSP furthermore comprises means for preventing effects on the feedback branch of a saturation of the signal delivered by the internal microphone (28), comprising: means (68) capable of concurrently analyzing i) the microphone signal delivered by the internal microphone (28) and ii) the accelerometer signal delivered by the motion sensor (64), and checking whether current characteristics of these microphonic and accelerometer signals verify or not a first set of predetermined criteria; and in the feedback branch upstream of the feedback filter ANC (54), a feedback saturation filter (70) selectively switchable depending on the result of checking the first set of criteria.
    [0002]
    The headset of claim 1, wherein: the feedback saturation filter (70) is one of a plurality of selectively switchable preconfigurable filters; and the DSP (50) further comprises: means (68) capable of selecting one of the preconfigured anti-saturation filters as a function of the result of the verification of the first set of criteria.
    [0003]
    3. The headset of claim 1, wherein: the DSP (50) further comprises: an equalization branch, comprising an equalization filter (58) capable of applying an equalization transfer function ( HE0) to the audio signal to be reproduced (M) before application thereof to the mixing means (60); and in the equalization branch upstream of the equalization filter (58), an equalization anti-saturation filter (72) selectively switchable at the same time as the feedback saturation filter (70).
    [0004]
    The headset of claim 1, wherein: the equalization anti-saturation filter (72) is one of a plurality of selectively switchable preconfigurable equalization filters; and the DSP (50) further comprises: means (68) capable of selecting one of the preconfigured equalization filters as a function of the result of the verification of the first set of criteria.
    [0005]
    The headset of claim 1, wherein the current characteristics of the accelerometer signal include an energy value (Rms, '') of the accelerometer signal, and the predetermined criteria include a threshold (Threshold a) which is compared with said energy value.
    [0006]
    The headset of claim 5, wherein the current characteristics of the microphone signal include energy values (Rms1, Rms2 ...) of the microphone signal in a plurality of respective frequency bands (Filter1, Filter2 ...). and the predetermined criteria comprise a series of respective thresholds (Threshold, Threshold2 Sez, d1N) to which said energy values of the microphonic signal are compared if the energy value (Rms, ') of the accelerometer signal exceeds said threshold ( Threshold a).
    [0007]
    The headset of claim 1, wherein: the feedback ANC filter (54) is one of a plurality of preconfigured, selectively switchable ANC feedback filters; and the DSP (50) furthermore comprises: means (62) for analyzing the signal delivered by the internal microphone, able to check whether the current characteristics of the signal delivered by the internal microphone satisfy a second set of criteria or not. predetermined; and selection means (62), able to select one of the preconfigured ANC feedback filters according to the result of the verification of the second set of criteria.
    [0008]
    The headset of claim 7, wherein: the DSP (50) further comprises: an equalization branch, comprising an equalization filter (58) adapted to apply an equalization transfer function ( HE0) to the audio signal to be reproduced (M) before application thereof to the mixing means (60); the equalization filter (58) is one of a plurality of preconfigurable, selectively switchable equalization filters; and the selection means (62) are also able to select one of the preconfigured equalization filters, as a function of the ANC current feedback filter selected.
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    FR3109687A1|2021-10-29|Acoustic System
    FR3039310A1|2017-01-27|ACTIVE NOISE CONTROL DEVICE
    FR2921747A1|2009-04-03|Portable audio signal i.e. music, listening device e.g. MPEG-1 audio layer 3 walkman, for e.g. coach, has analyzing and transferring unit transferring external audio signal that informs monitoring of sound event to user, to listening unit
    同族专利:
    公开号 | 公开日
    EP2945399A1|2015-11-18|
    EP2945399B1|2016-10-12|
    CN105100990A|2015-11-25|
    FR3021180B1|2016-06-03|
    JP2015219527A|2015-12-07|
    US9466281B2|2016-10-11|
    US20150332662A1|2015-11-19|
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    法律状态:
    2015-05-26| PLFP| Fee payment|Year of fee payment: 2 |
    2015-11-20| PLSC| Search report ready|Effective date: 20151120 |
    2016-05-24| PLFP| Fee payment|Year of fee payment: 3 |
    2016-11-11| TP| Transmission of property|Owner name: PARROT DRONES, FR Effective date: 20161010 |
    2017-05-16| PLFP| Fee payment|Year of fee payment: 4 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1454406A|FR3021180B1|2014-05-16|2014-05-16|AUDIO ACTIVE ANC CONTROL AUDIO HELMET WITH PREVENTION OF THE EFFECTS OF A SATURATION OF THE MICROPHONE SIGNAL "FEEDBACK"|FR1454406A| FR3021180B1|2014-05-16|2014-05-16|AUDIO ACTIVE ANC CONTROL AUDIO HELMET WITH PREVENTION OF THE EFFECTS OF A SATURATION OF THE MICROPHONE SIGNAL "FEEDBACK"|
    US14/692,541| US9466281B2|2014-05-16|2015-04-21|ANC noise active control audio headset with prevention of the effects of a saturation of the feedback microphone signal|
    EP15166492.7A| EP2945399B1|2014-05-16|2015-05-06|Audio headset with active noise control anc with prevention of the effects of saturation of a microphone signal feedback|
    JP2015099577A| JP2015219527A|2014-05-16|2015-05-15|Anc noise active control audio head set preventing influence of saturation of feedback microphone signal|
    CN201510253234.1A| CN105100990A|2014-05-16|2015-05-18|Audio headset with active noise control ANC with prevention of effects of saturation of microphone signal feedback|
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