Gain adjustment in an ANR system with multiple feedforward microphones

Abstract

The technology described in this document can be embodied in a method comprising: receiving a first input signal representing audio captured by a first sensor disposed in a signal path of an active noise reduction (ANR) device; and receiving a second input signal representing audio captured by a second sensor disposed in the signal path of the ANR device. The method also includes processing the first input signal and the second input signal by at least one compensator to generate a drive signal for an acoustic transducer of the ANR device. The gain applied to the signal path is reduced by at least 3 dB relative to an ANR signal path having a single sensor.

Description

Technical Field

[0001] The present disclosure generally relates to active noise reduction (ANR) devices having multiple feed-forward microphones. Background Art

[0002] Acoustic devices such as headphones may include active noise reduction (ANR) capabilities that block and constructively cancel at least a portion of ambient noise from reaching the user's ears. Thus, ANR devices produce an acoustic isolation effect, thereby isolating the user at least partially from the environment. Summary of the invention

[0003] In general, in one aspect, the document features a method comprising: receiving a first input signal representing audio captured by a first sensor disposed in a signal path of an active noise reduction (ANR) device; and receiving a second input signal representing audio captured by a second sensor disposed in the signal path of the ANR device. The method also includes processing the first input signal and the second input signal by at least one compensator to generate a drive signal for an acoustic transducer of the ANR device. A gain applied to the signal path is reduced by at least 3 dB relative to an ANR signal path having a single sensor.

[0004] In another aspect, the document features an active noise reduction (ANR) device that includes a first sensor disposed in a signal path of the device and configured to generate a first audio input signal. The ANR device also includes: a second sensor disposed in a signal path of the ANR device and configured to generate a second audio input signal; and at least one compensator configured to receive and process the first audio input signal and the second audio input signal to generate a drive signal for an acoustic transducer of the ANR device. The gain of the signal path is reduced by at least 3 dB relative to an ANR signal path having a single sensor.

[0005] In another aspect, the document features one or more machine-readable storage devices having computer-readable instructions encoded thereon for causing one or more processing devices to perform various operations. The operations include: receiving a first input signal representing audio captured by a first sensor disposed in a signal path of an active noise reduction (ANR) device; and receiving a second input signal representing audio captured by a second sensor disposed in the signal path of the ANR device. The operations also include processing the first input signal and the second input signal to generate a drive signal for an acoustic transducer of the ANR device. The gain of the signal path is reduced by at least 3 dB relative to an ANR signal path having a single sensor.

[0006] Specific implementations of the above aspects may include one or more of the following features.

[0007] Processing the first input signal and the second input signal to generate a drive signal may include: combining the first input signal and the second input signal to generate a combined input signal, applying a gain to the combined input signal using an amplifier, and filtering the output of the amplifier by the at least one compensator to generate a drive signal for the acoustic transducer. The amplifier may be provided as part of the at least one compensator. Processing the first input signal and the second input signal to generate a drive signal may include: applying a first gain to the first input signal using a first amplifier to generate a first amplified input signal, and filtering the first amplified input signal by the first compensator to generate a first processed signal for the acoustic transducer of the ANR device. The processing also includes: applying a second gain to the second input signal using a second amplifier to generate a second amplified input signal, and filtering the second input signal by the second compensator to generate a second processed signal for the acoustic transducer of the ANR device. The processing also includes combining the first processed signal and the second processed signal to generate the drive signal for the acoustic transducer. The first compensator may apply one or more filters to the first amplified input signal, and the second compensator may apply one or more filters to the second amplified input signal. The one or more filters applied to the second amplified signal may be different from the one or more filters applied to the first amplified signal. Processing the first input signal and the second input signal to generate a drive signal may include: processing the first input signal by a first compensator to generate a first processed signal for the acoustic transducer of the ANR device, processing the second input signal by a second compensator to generate a second processed signal for the acoustic transducer of the ANR device, and combining the first processed signal and the second processed signal to generate a drive signal for the acoustic transducer. The first compensator may apply a first gain and use one or more filters to generate the first processed signal. The second compensator may apply a second gain and use one or more filters to generate the second processed signal. Processing the first input signal and the second input signal to generate a drive signal may include: applying a first gain to the first input signal using a first amplifier, applying a second gain to the second input signal using a second amplifier, combining the first input signal and the second input signal to generate a combined input signal, and filtering the combined input signal by the at least one compensator to generate a drive signal for the acoustic transducer. The first amplifier and the second amplifier may be part of the at least one compensator.

[0008] Two or more features described in this disclosure, including those described in the Summary of the Invention, may be combined to form embodiments not specifically described herein. The details of one or more specific implementations are discussed in the accompanying drawings and the following description. Other features, objects, and advantages will be apparent in the specification, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 An example of an active noise reduction (ANR) system deployed in headphones is shown.

[0010] Figure 2 is a block diagram of an exemplary configuration of an ANR system.

[0011] Figure 3 is a block diagram of a feed-forward compensator having an ANR signal flow path arranged in parallel with a through signal flow path.

[0012] Figure 4 is a block diagram of an ANR system with multiple feed-forward sensors.

[0013] Figure 5 is a block diagram of an ANR system with multiple feedforward sensors having independently controllable gains.

[0014] Figure 6 is a block diagram of an ANR system having multiple feedforward sensors with independently controllable gains and independent compensators.

[0015] Figure 7 is a flow chart of an exemplary process for generating a drive signal in an ANR system having a plurality of sensors disposed in a signal path.

[0016] Figure 8 is a block diagram of an example of a computing device. DETAILED DESCRIPTION

[0017] This document describes a technique for using multiple feed-forward microphones in an active noise reduction (ANR) system to improve ANR performance, noise performance, and reduce the possibility of unstable conditions. When, for example, an ANR system is deployed in a noise cancellation headset, certain unstable conditions may cause the headset to produce acoustic artifacts (e.g., loud noises) that are uncomfortable for the user. By providing multiple feed-forward microphones in an ANR system, the techniques described herein reduce the gain through each feed-forward signal path relative to the case of using a single feed-forward microphone. Since the gain through a separate signal path is lower, there is more headroom in the system, resulting in a reduced chance of clipping, and there is more margin to handle instabilities that may be generated, for example, due to coupling between one of the feed-forward microphones and the transducer. In addition, the individual gains of multiple feed-forward microphones can be allocated according to the possibility of their coupling, so that the total target gain is not affected compared to the single microphone case. For example, if one of the microphones is located in a position where the microphone is easily coupled to a driver (and, by extension, susceptible to instability), a lower gain can be applied to the microphone to reduce the possibility of coupling. However, the gain of the other microphone can be adjusted accordingly so that the target total gain of the feed-forward microphone is not reduced. In one example, the overall target gain can be distributed between the two feedforward paths so that the first microphone that is more easily coupled has a gain of 0.25, while the second microphone that is less easily coupled has a gain of 0.75. Therefore, although the gain of the individual signal paths is reduced compared to the overall (for example, in order to make the ANR system tolerant to non-ideal microphone positions, such as microphone positions closer to the earmuff periphery or near the port, where there may be greater coupling between the microphone and the transducer), the overall feedforward gain is not affected due to the weighted distribution of gains between multiple feedforward paths. In some specific implementations, the weighting can also be done on a frequency-by-frequency basis so that the gain distribution between two or more feedforward paths is different for different frequencies (or frequency ranges).

[0018] Active noise reduction (ANR) systems can be deployed in various acoustic devices to eliminate or reduce unwanted or unpleasant noise. For example, ANR headphones can provide a potential immersive listening experience by reducing the impact of ambient noise and sound. As used herein, the term headphones include various types of such personal acoustic devices, such as in-ear, circum-ear or hanging ear headphones, earplugs and hearing aids. ANR systems can also be used in automobiles or other transportation systems (e.g., for cars, trucks, buses, airplanes, ships or other vehicles) to eliminate or attenuate unwanted noise such as generated by mechanical vibrations or engine harmonics.

[0019] In some cases, the ANR system may include an electroacoustic or electromechanical system that may be configured to eliminate at least some of the undesirable noise (commonly referred to as the main noise) based on the principle of superposition. For example, the ANR system can identify the amplitude and phase of the main noise and generate another signal (commonly referred to as an anti-noise signal) of approximately the same amplitude and anti-phase. The anti-noise signal can then be combined with the main noise so that both are substantially eliminated at the desired location. As used herein, the term substantially eliminated may include reducing the "eliminated" noise to a specified level or to within an acceptable tolerance, and does not require complete elimination of all noise. The ANR system can be used to attenuate a wide range of noise signals, including, for example, broadband noise and / or low-frequency noise, which may not be easily attenuated using passive noise control systems.

[0020] Figure 1 An example of an ANR system 100 deployed in a headset 102 is shown. The headset 102 includes an earmuff 104 on each side that fits on, around, or over a user's ear. The earmuff 104 may include a layer 106 of soft material (e.g., soft foam) to comfortably fit over the user's ear. The ANR system 100 may include or otherwise be coupled to a feedforward sensor 108, a feedback sensor 110, and an acoustic transducer 112. The feedforward sensor 108 may be a microphone or another acoustic sensor and may be disposed on or near the exterior of the earmuff 104 to detect ambient noise. The feedback sensor 110 may be a microphone or another acoustic sensor and may be deployed proximate to the user's ear canal and / or the transducer 112. The transducer 112 may be an acoustic transducer that transmits audio signals from an audio source device (not shown) to which the headset 102 is connected and / or other signals from the ANR system 100. Although Figure 1 An example of an ANR system being deployed in a circumaural headphone is shown, but the ANR system may also be deployed in other form factors, including in-ear headphones, over-ear headphones, or off-ear personal acoustic devices (e.g., devices designed not to contact the wearer's ears, but to be worn near the wearer's ears on the wearer's head or body).

[0021] The ANR system 100 may be configured to process the signal detected by the feedforward sensor 108 and / or the feedback sensor 110 to generate the anti-noise signal provided to the transducer 112. The ANR system 100 may be of various types. In some implementations, the ANR system 100 is based on feedforward noise elimination, wherein the main noise is sensed by the feedforward sensor 108 before the noise reaches the secondary source such as the transducer 112. In some implementations, the ANR system 100 may be based on feedback noise elimination, wherein the ANR system 100 eliminates the main noise based on the residual noise detected by the feedback sensor 110 and without the beneficial effect of the feedforward sensor 108. In some implementations, both feedforward noise elimination and feedback noise elimination are used. The ANR system 100 may be configured to control noise in various frequency bands. In some implementations, the ANR system 100 may be configured to control broadband noise such as white noise. In some implementations, the ANR system 100 may be configured to control narrowband noise such as harmonic noise from a vehicle engine.

[0022] In some implementations, the ANR system 100 may include a configurable digital signal processor (DSP) and other circuitry to implement various signal flow topologies and filter configurations. Examples of such DSPs are described in U.S. Patents 8,073,150 and 8,073,151, which are incorporated herein by reference in their entirety. Various signal flow topologies may be implemented in the ANR system 100 to implement functions such as audio equalization, feedback noise cancellation, and feedforward noise cancellation. For example, Figure 2 As shown, the signal flow topology of the ANR system 100 may include a feedforward signal flow path 114 that drives the transducer 112 (using, for example, a feedforward compensator 116) to generate an anti-noise signal to reduce the effects of a noise signal picked up by the feedforward sensor 108. As another example, the signal flow topology may include a feedback signal flow path 118 that drives the transducer 112 (using, for example, a feedback compensator 120) to generate an anti-noise signal to reduce the effects of a noise signal picked up by the feedback sensor 110. The signal flow topology may also include an audio path 122 that includes circuitry (e.g., an equalizer 124) for processing an input audio signal 126 such as a music or communication signal for playback on the transducer 112.

[0023] In some implementations, the headset 102 may include a feature that may be referred to as a "transparent mode" or "hear-through mode". In this mode, the feedforward sensor 108 or other detection device may be used to detect external sounds that the user may want to hear, and the ANR system 100 may be configured to transmit such sounds reproduced by the transducer 112. In some cases, the sensor for the transparent feature may be a sensor separate from the feedforward sensor 108, such as a microphone. In some implementations, signals captured by multiple sensors may be used (e.g., using a beamforming process) to, for example, focus on another source of the user's voice or ambient sound. In some implementations, the headset 102 may allow multi-mode operation including a hear-through mode, in which the ANR function may be turned off or at least reduced within at least a certain frequency range (e.g., the voice band) to allow relatively wideband ambient sounds to reach the user. In some implementations, the ANR system 100 may also be used to shape the frequency response of the signal passing through the headset. For example, the feedforward compensator 116 and / or the feedback compensator 120 may be used to change the acoustic experience of an earbud blocking the ear canal to an acoustic experience in which ambient sounds (eg, the user's own voice) sound more natural to the user.

[0024] In some implementations, the ANR system 100 can allow a user to control the amount of ambient noise passing through the device while maintaining ANR functionality, such as described in U.S. Patent No. 10,096,313, which is incorporated herein by reference in its entirety. For example, to allow for an intermediate target insertion gain between 0 and 1 and to enable a user to control the amount of ambient noise passing through the device, the feedforward compensator 116 can include an ANR filter 302 and a pass-through filter 304 arranged in parallel, wherein the gain of the pass-through filter can be adjusted by a coefficient C, such as Figure 3 The adjustable gain C can be implemented using a variable gain amplifier (VGA) disposed in the through signal flow path of the feedforward compensator 116 .

[0025] In an implementation where the earphone 102 includes a hear-through mode, some conditions may lead to the onset of an unstable condition. For example, if the output of the transducer 112 is fed back to the feedforward sensor 108, and the ANR system 100 transmits a signal back to the transducer 112, a rapidly deteriorating unstable condition may occur, resulting in undesirable sound emanating from the transducer 112. This condition may be demonstrated, for example, by cupping a hand over the earphone to facilitate a feedback path between the transducer 112 and the feedforward sensor 108. Such a feedback path may be established during use of the earphone, for example, if a user wears a hat (e.g., a hood or winter cap) over the earphone 102.

[0026] In some implementations, an unstable condition may occur even when the earphone 102 does not include a hear-through mode. For example, an unstable condition may occur due to a change in the transfer function of a secondary path of the ANR system 100 (e.g., an acoustic path between the feedback sensor 110 and the transducer 112). For example, such a condition may occur if the acoustic path between the transducer 112 and the feedback sensor 110 changes in size or shape. Such a condition may be demonstrated, for example, by blocking an opening through which sound is emitted from the earphone 102 (e.g., using a finger or palm). In the case of an earphone having a nozzle with an acoustic channel that acoustically couples the front cavity of the acoustic transducer to the ear canal of the user, such a condition may be referred to as a blocked nozzle condition. In practice, such a condition may occur, for example, during placement / removal of the earphone into / from the ear. This effect may be particularly observable in smaller earphones (e.g., in-ear earphones) or in-ear hearing aids, where the secondary path may change if the earphone or hearing aid moves while being worn. For example, moving in-ear headphones or hearing aids can cause the volume of air in the corresponding secondary path to change, causing the ANR system to become unstable. In some cases, pressure fluctuations in the ambient air may also cause the ANR system to become unstable. For example, when a vehicle door or window (e.g., a bus door) is closed, the accompanying pressure changes may cause the ANR system to become unstable. Another example of a pressure fluctuation that can lead to an unstable condition is a significant change in the ambient pressure of the air relative to the normal atmospheric pressure at sea level.

[0027] Unless the unstable condition is detected and resolved quickly, the unstable condition may cause the transducer 112 to produce acoustic artifacts (e.g., loud audible noise) that may be uncomfortable to the wearer. The technology described herein uses multiple feedforward sensors such as microphones to improve ANR performance and reduce the possibility of unstable conditions. In some specific implementations, when multiple feedforward sensors are used in the ANR system 100, the gain through each feedforward path can be lower than when a single feedforward sensor is used. Therefore, the compensators, filters, and other circuits in any individual signal path can have a lower total gain than when a single feedforward sensor is used. In addition, since the gain of any individual signal path is lower than when a single sensor is used, there is more headroom in the system, resulting in a reduced chance of clipping, and providing more margin to prevent instability, such as may be caused by coupling between the feedforward sensor and the transducer. As used herein, the term headroom refers to the difference between the signal processing capability of an electrical component and the maximum level of a signal in a signal path (such as a feedforward signal path). The reduced gain applied to any individual signal path may also make the ANR system better tolerant of non-ideal sensor locations, such as sensor locations closer to the periphery of the ear cup 104 where the likelihood of coupling between the sensor and the transducer may be higher than for sensors located at greater distances from the periphery of the ear cup 104.

[0028] Figure 4 It is a block diagram of an ANR system 400 having a plurality of feedforward sensors 402a, 402b, ..., 402N arranged along a feedforward path 114. Each of the feedforward sensors 402a, 402b, 402N can be an analog microphone, a digital microphone, or another acoustic sensor, and can be arranged on or near the outside of the earmuff 104 to detect ambient noise. In some specific implementations, each of the feedforward sensors 402a, 402b, ..., 402N can be positioned to detect ambient noise incident from a specific direction and / or detect certain types or frequencies of ambient noise, such as the voice of a user. The number of feedforward sensors included in the ANR system 400 can be as few as two sensors. Typically, there is no upper limit to the number of feedforward sensors that can be included in the ANR system 400. In some specific implementations, practical considerations, such as space and cost, can create an upper limit for the number of sensors included in the system. In some specific implementations, technical limitations of other circuits (such as compensators or transducers) in the feedforward path 114 can create an upper limit for the number of sensors included in the system. Although the ANR system 400 is described in the context of being deployed within the headset 102, the techniques described herein are equally applicable to ANR systems deployed in other contexts, such as an automobile or other transportation system.

[0029] The ambient noise signals generated by each of the feedforward sensors 402a, 402b, ..., 402N in the ANR system 400 can be combined using a combining circuit 404, such as a summing circuit. It should be understood that the combining circuit 404 can perform the summing in the digital or analog domain, and the position of the combining circuit 404 can vary along the feedforward signal path 114. Although not shown, it should also be understood that the feedforward signal path 114 can include additional circuits, such as amplifiers and analog-to-digital converters. The gain of the combined signal can be adjusted using a variable gain amplifier (VGA) 406 or other amplification circuit disposed in the feedforward path 114 by a gain factor G. ff To adjust. Gain factor G ff The gain factor may be a reduced gain factor relative to a gain factor applied in an ANR system having a single feedforward sensor, as described in detail below. The feedforward compensator 116 may process the combined ambient noise signal to generate, for example, an anti-noise signal. In some implementations, the feedforward compensator 116 may include an ANR signal flow path arranged in parallel with the through signal flow path to provide at least a portion of the ambient noise to the user, as described in reference to FIG. Figure 3 In some implementations, the VGA 406 can be included in the feed-forward compensator 116. The signal generated by the feed-forward compensator 116 can be combined with other signals in the ANR system 400 (such as signals from the feedback path 118 and / or the audio path 122), and the resulting signal can be provided to the transducer 112.

[0030] In some implementations, the gain factor G ff can be selected by the ANR system 400 based on the number of feedforward sensors 402a, 402b, ..., 402N present in the system. For example, if the ANR system 400 includes two feedforward sensors, the gain factor G ff The gain factor G can be reduced by up to 50% relative to an ANR system with a single feedforward sensor, which can be about 6 decibels (dB) in one example. In other cases, if the ANR system 400 includes three feedforward sensors, the gain factor G ff The gain factor G can be reduced by up to 67% relative to an ANR system with a single feedforward sensor, which can be about 9dB to 10dB in one example. In other cases, if the ANR system 400 includes four feedforward sensors, the gain factor G ff The reduction can be up to 75% relative to an ANR system with a single feed-forward sensor, which in one example can be approximately 12 dB.

[0031] In some cases, the ANR system 400 may adjust the gain factor G based on the intended application of the system, the requirements of other parts of the system, or other practical considerations. ffFor example, if the ANR system 400 includes two feedforward sensors, the gain factor G ff Relative to an ANR system with a single feedforward sensor, the gain can be reduced by up to 50%, as described above. However, the ANR system 400 may reduce the gain by an amount less than 50% relative to an ANR system with a single feedforward sensor to account for, for example, the signal level requirements of the feedforward compensator 116.

[0032] The lower overall gain reduces the likelihood that coupling between, for example, the transducer 112 and one or more of the feedforward sensors 402a, 402b, ..., 402N will result in instability. This in turn allows for non-ideal placement of one or more of the feedforward sensors 402a, 402b, ..., 402N (e.g., near a location where acoustic leakage may result in coupling with the driver, such as near the periphery of an ear cup or near an acoustic port). In addition, combining the ambient noise signals detected by multiple feedforward sensors can produce a combined ambient noise signal having a higher signal-to-noise ratio than the ambient noise signal from a single sensor. For example, when the random noise generated by each feedforward path is uncorrelated with each other feedforward path, the total combined noise can be reduced by a certain amount (e.g., 3dB) per pair of combinations while obtaining a higher total signal amount (e.g., 6dB) per pair of combinations. This improves the performance of the ANR system 400 by, for example, reducing the background noise and providing a more reliable signal for processing to generate an anti-noise signal.

[0033] Figure 5 1 shows a block diagram of an ANR system 500 having a plurality of feedforward sensors 402a, 402b, ..., 402N arranged along a feedforward signal path 114. Figure 5 As shown, each feedforward sensor 402a, 402b, ..., 402N can be coupled to a corresponding VGA 502a, 502b, ..., 502N. Each of the VGAs 502a, 502b, ..., 502N can be configured to apply a corresponding gain factor G to the ambient noise signal generated by the corresponding feedforward sensor. ff1 , G ff2 , …, G ffN For example, VGA 502a may be coupled to feedforward sensor 402a and may apply a gain factor G to the signal generated by feedforward sensor 402a. ff1, and so on. This in turn allows the gains of different feedforward microphones to be adjusted individually, so that a microphone that is more easily coupled to the driver has a lower gain than another microphone that is less easily coupled. Additionally, the overall target gain can be distributed across the different microphones so that the overall feedforward gain is at a target level. For example, the overall target gain can be distributed between two feedforward microphones so that the first microphone that is more easily coupled has a gain of 0.25, while the second microphone that is less easily coupled has a gain of 0.75.

[0034] The signals output by each of the VGAs 502a, 502b, ..., 502N can be combined using a combining circuit 404 (e.g., a circuit including one or more adders). It should be understood that the combining circuit 404 can perform the summation in the digital or analog domain, and the location of the combining circuit 404 can vary along the feedforward signal path 114. Although not shown, it should also be understood that the feedforward signal path 114 can include additional circuits, such as amplifiers and analog-to-digital converters. The feedforward compensator 116 can process the combined signal to produce, for example, an anti-noise signal. In some embodiments, the feedforward compensator 116 can include an ANR signal flow path arranged in parallel with the through signal flow path to provide at least a portion of the ambient noise to the user, as shown in reference Figure 3 The signal generated by the feedforward compensator 116 may be combined with other signals in the ANR system 500 (such as signals from the feedback path 118 and / or the audio path 122), and the resulting signal may be provided to the transducer 112. Figure 5 The VGA 502 and the combining circuit 404 are shown as separate entities from the feed-forward compensator 116 , but in some implementations, the VGA 502 and the combining circuit 404 may be included as part of the feed-forward compensator 116 .

[0035] The individual gain applied by each of the VGAs 502a, 502b, ..., 502N may be reduced relative to the gain applied in an ANR system having a single feedforward sensor. This, in turn, reduces the likelihood of unstable conditions in the system and improves ANR performance. The amount of gain reduction may be determined by the ANR system 500 based on, for example, the number of feedforward sensors present in the system (e.g., reference 502). Figure 4 In addition, by providing a separate VGA 502a, 502b, ..., 502N for each of the feed-forward sensors 402a, 402b, ..., 402N, the ANR system 500 can individually adjust the gain applied to the ambient noise signal generated by the corresponding feed-forward sensor (e.g., by adjusting the G ff1 , G ff2 , …, G ffNIn this case, the ANR system 500 may apply control to the individual ambient noise signals before they are combined and processed by the feed-forward compensator 116, without affecting the target overall gain of the feed-forward path.

[0036] refer to Figure 6 In some implementations, the ANR system 600 may include a separate compensator 602a, 602b, ..., 602N for each of the feedforward sensors 402a, 402b, ..., 402N. Figure 6 As shown, each compensator 602a, 602b, ..., 602N can be coupled to a corresponding feedforward sensor 402a, 402b, ..., 402N via a VGA 502a, 502b, ..., 502N. In some implementations, a separate compensator for each feedforward sensor 402 allows for separate frequency-dependent filtering and / or gain allocation for different feedforward paths. For example, if a particular microphone is located near a periphery or port that may be coupled to a high-frequency driver, a digital filter may be placed in the corresponding compensator K. ff to reduce the likelihood of such coupling. Such digital filters can be configured to filter out a portion of the spectrum of the signal captured by a particular microphone to reduce the likelihood of coupling. In some cases, if the sensors / microphones 402 are far apart from each other on the ear cups or earpieces, the signals captured by the microphones may be uncorrelated with each other. In this case, the K filter can be applied to each microphone individually. ff To weight different frequencies differently.

[0037] In some implementations, each compensator 602a, 602b, ..., 602N may include a corresponding VGA 502a, 502b, ..., 502N. Each compensator 602a, 602b, ..., 602N may include one or more filters, controllers, or other circuits to process the signal generated by the corresponding feedforward sensor to generate, for example, an anti-noise signal. In some implementations, each compensator 602a, 602b, ..., 602N may include an ANR signal flow path arranged in parallel with the through signal flow path to provide at least a portion of the ambient noise to the user, as shown in FIG. Figure 3As described. The signals output by each compensator in compensators 602a, 602b, ..., 602N can be combined using a combining circuit 404. It should be understood that the combining circuit 404 can perform summation in the digital or analog domain, and the position of the combining circuit 404 can change along the feedforward signal path 114. Although not shown, it should also be understood that the feedforward signal path 114 may include additional circuits, such as amplifiers and analog-to-digital converters. The resulting signal can be combined with other signals in the ANR system 600 (such as signals from the feedback path 118 and / or the audio path 122), and the resulting signal can be provided to the transducer 112.

[0038] Figure 7 is a flow chart of an exemplary process for generating a drive signal in an ANR system having a plurality of acoustic sensors disposed in a signal path. At least a portion of process 700 may be implemented using one or more processing devices, such as the DSPs described in U.S. Patents 8,073,150 and 8,073,151, which are incorporated herein by reference in their entireties. Operations of process 700 include receiving a first input signal representing audio captured by a first sensor disposed in a signal path of the ANR device (702). Operations of process 700 also include receiving a second input signal representing audio captured by a second sensor disposed in a signal path of the ANR device (704). In some implementations, each of the first sensor and the second sensor includes a microphone, such as a feed-forward microphone of the ANR device. In some implementations, the ANR device may be a circumaural headphone, such as that of reference 1. Figure 1 In some implementations, the ANR device may include, for example, in-ear headphones, over-ear headphones, open-ear headphones, hearing aids, or other personal acoustic devices. In some implementations, the audio captured by the first sensor and / or the second sensor may be ambient noise associated with the ANR device. In some implementations, the signal path may be a feedforward signal path of the ANR device. In some implementations, the gain of the signal path may be reduced relative to an ANR signal path having only the first input signal, as described in reference to Figures 4 to 6 described.

[0039] The operation of process 700 also includes processing the first input signal and the second input signal by at least one compensator and / or a variable gain amplifier to generate a drive signal for an acoustic transducer of the ANR device (706). In some implementations, the at least one compensator may include a feedback compensator and / or a feedforward compensator, such as a reference Figure 2In some implementations, the at least one compensator may include a compensator having an ANR signal flow path arranged in parallel with the through signal flow path to provide at least a portion of the ambient noise to the user, as described in reference Figure 3 In some implementations, the drive signal can be combined with one or more additional signals (e.g., signals generated in the audio path of the ANR device) before being provided to the acoustic transducer. Thus, the audio output of the acoustic transducer can represent the noise-reduced audio combined with the audio representing the environment adjusted according to the user's preferences.

[0040] In some implementations, the processing in step 706 includes combining the first input signal and the second input signal to generate a combined input signal, applying a gain to the combined input signal using an amplifier, and processing an output of the amplifier using at least one compensator to generate a drive signal for the acoustic transducer, as described in reference to Figure 4 In some specific implementations, the processing includes applying a first gain to a first input signal using a first amplifier, applying a second gain to a second signal using a second amplifier, combining the first input signal and the second input signal to generate a combined input signal, and processing the combined input signal using at least one compensator to generate a drive signal for the acoustic transducer, as described in reference Figure 5 In some specific implementations, the processing includes processing a first input signal using a first variable gain amplifier and a compensator to generate a first processed signal for an acoustic transducer of the ANR device, processing a second input signal using a second variable gain amplifier and a compensator to generate a second processed signal for the acoustic transducer of the ANR device, and combining the first processed signal and the second processed signal to generate a drive signal for the acoustic transducer, as described in reference Figure 6 In each case, it will be appreciated that the variable gain amplifier may be included within a respective compensator associated with the respective feed-forward signal path.

[0041] Although Figures 4 to 6 A particular exemplary arrangement of components for implementing the techniques described herein is shown, but other components and / or arrangements of components may be used without departing from the scope of the present disclosure. In some implementations, the arrangement of components along the feedforward path may include an analog microphone, an amplifier, an analog-to-digital converter (ADC), a digital adder (in the case of multiple microphones), a VGA, and a feedforward compensator (in that order). This arrangement is similar to Figure 4, where an amplifier and ADC are added between each microphone 402 and the combining circuit 404 (in this example, including a digital adder). In some implementations, the arrangement of components along the feedforward path may include an analog microphone, an analog adder (in the case of multiple microphones), an ADC, a VGA, and a feedforward compensator. This arrangement is also similar to Figure 4 , wherein the combination circuit 404 includes an analog adder and an ADC disposed between the combination circuit 404 and the VGA 406. The arrangement of the components can be selected based on the target performance parameters. For example, in applications where limiting quantization noise is important, the latter arrangement can be selected because it only introduces a single noise source (ADC) before the gain stage. However, this may be at the expense of dynamic range issues (because the signals from all microphones pass through a single ADC), which in turn may result in clipping of the signals captured by some microphones. On the other hand, if avoiding clipping is more important at the expense of potentially more quantization noise, the former arrangement (where the amplifier and ADC are disposed between each microphone 402 and the combination circuit 404) can be used.

[0042] Figure 8 800 is a block diagram of an exemplary computer system 800 that can be used to perform the above operations. For example, at least a portion of the computer system 800 can be used to implement the above referenced Figure 4 , Figure 5 and Figure 6 Any of the systems 400, 500 and 600 described above. System 800 includes a processor 810, a memory 820, a storage device 830 and an input / output device 840. Each of the components 810, 820, 830 and 840 can be interconnected, for example, using a system bus 850. Processor 810 is capable of processing instructions for execution within system 800. In one specific implementation, processor 810 is a single-threaded processor. In another specific implementation, processor 810 is a multi-threaded processor. Processor 810 is capable of processing instructions stored in memory 820 or on storage device 830.

[0043] The memory 820 stores information within the system 800. In one implementation, the memory 820 is a computer readable medium. In one implementation, the memory 820 is a volatile memory unit. In another implementation, the memory 820 is a non-volatile memory unit.

[0044] The storage device 830 can provide mass storage for the system 800. In one implementation, the storage device 830 is a computer-readable medium. In various implementations, the storage device 830 may include, for example, a hard disk device, an optical disk device, a storage device shared on a network by multiple computing devices (e.g., a cloud storage device), or some other large-capacity storage device.

[0045] The input / output devices 840 provide input / output operations for the system 800. In one implementation, the input / output devices 840 may include one or more network interface devices (e.g., Ethernet cards), serial communication devices (e.g., RS-232 ports), and / or wireless interface devices (e.g., 802.11 cards). In another implementation, the input / output devices may include driver devices configured to receive input data and send output data to other input / output devices, such as keyboards, printers, and display devices 860 and acoustic transducers / speakers 870.

[0046] although Figure 8 An exemplary processing system has been described in the specification, but the specific implementation of the subject matter and functional operations described in this specification may be implemented in other types of digital electronic circuits, in computer software, firmware or hardware (including the structures disclosed in this specification and their structural equivalents), or in a combination of one or more of them.

[0047] This specification uses the term "configured" in conjunction with system and computer program components. For a system of one or more computers, being configured to perform a particular operation or action means that software, firmware, hardware, or a combination thereof has been installed on the system that causes the system to perform those operations or actions in operation. For one or more computer programs, being "configured to" perform a particular operation or action means that the one or more programs include instructions that, when executed by a data processing device, cause the device to perform the operation or action.

[0048] The embodiments of the subject matter and functional operations described in this specification may be implemented in digital electronic circuits, in tangibly embodied computer software or firmware, in computer hardware (including the structures disclosed in this specification and their structural equivalents), or in a combination of one or more of them. The embodiments of the subject matter described in this specification may be implemented as one or more computer programs, that is, one or more modules of computer program instructions encoded on a tangible non-transitory storage medium for execution by a data processing device or for controlling the operation of a data processing device. The computer storage medium may be a machine-readable storage device, a machine-readable storage substrate, a random or serial access memory device, or a combination of one or more of them. Alternatively or in addition, program instructions may be encoded on an artificially generated propagation signal, which (e.g., a machine-generated electrical signal, optical signal, or electromagnetic signal) is generated to encode information for transmission to a suitable receiving device for execution by a data processing device.

[0049] The term "data processing apparatus" refers to data processing hardware and encompasses all types of apparatus, devices and machines for processing data, including, for example, a programmable processor, a computer or multiple processors or computers. The apparatus may also be or include dedicated logic circuits, such as an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit). In addition to hardware, the apparatus may optionally include code that creates an execution environment for a computer program, such as code constituting processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them.

[0050] A computer program may also be referred to or described as a program, software, software application, application, module, software module, script or code, and may be written in any form of programming language, including compiled or interpreted languages, or declarative or procedural languages, and may be deployed in any form, including as a stand-alone program or as a module, component, subroutine or other unit suitable for use in a computing environment. A program may, but need not, correspond to a file in a file system. A program may be stored in a portion of a file that holds other programs or data, such as one or more scripts stored in a markup language document, in a single file dedicated to the program under consideration, or in multiple coordinated files, such as files that store portions of one or more modules, subroutines or code. A computer program may be deployed on one computer or executed on multiple computers distributed at one site or multiple sites and interconnected by a data communications network.

[0051] The processes and logic flows described in this specification can be performed by one or more programmable computers executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by a dedicated logic circuit (e.g., an FPGA or ASIC) or by a combination of a dedicated logic circuit and one or more programmed computers.

[0052] To provide interaction with a user, embodiments of the subject matter described in this specification may be implemented on a computer having a display device (e.g., a light emitting diode (LED) or liquid crystal display (LCD) monitor) for displaying information to the user and having a keyboard and pointing device (e.g., a mouse or trackball) through which the user can provide input to the computer. Other types of devices may also be used to provide interaction with a user; for example, the feedback provided to the user may be any form of sensory feedback, such as visual feedback, auditory feedback, or tactile feedback; and any form of input from the user may be received, including acoustic, voice, or tactile input. In addition, a computer may interact with a user by sending and receiving documents to and from a device used by the user; for example, by sending a web page to a web browser in response to a request received from a web browser on a user's device. In addition, a computer may interact with a user by sending a text message or other form of message to a personal device (e.g., a smartphone running a messaging application) and receiving a response message in return from the user.

[0053] Embodiments of the subject matter described in this specification may be implemented in a computing system that includes a back-end component (e.g., as a data server), or includes a middleware component (e.g., an application server), or includes a front-end component (e.g., a client computer with a graphical user interface, a web browser, or an application through which a user can interact with a specific implementation of the subject matter described in this specification), or any combination of one or more of such back-end components, middleware components, or front-end components. The components of the system may be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include local area networks (LANs) and wide area networks (WANs), such as the Internet.

[0054] The computing system may include a client and a server. The client and the server are usually far away from each other and usually interact through a communication network. The relationship between the client and the server is generated by means of a computer program that runs on a corresponding computer and has a client-server relationship with each other. In some embodiments, the server transfers data (e.g., an HTML page) to a user device, for example, in order to display data to a user interacting with the device and receive user input from the user, the user acting as a client. The data generated at the user device, for example, the result of the user interaction, can be received from the device at the server.

[0055] Other examples and applications not specifically described herein are also within the scope of the following claims. The elements of the different specific implementations described herein can be combined to form other examples not specifically set forth above. Some elements can be removed from the structure described herein without adversely affecting their operation. In addition, various independent elements can be combined into one or more separate elements to perform the functions described herein.

Claims

1. A method implemented in an active noise reduction (ANR) device, the method comprising: receiving a first input signal representing audio captured by a first sensor disposed in a signal path of the ANR device; receiving a second input signal representing audio captured by a second sensor disposed in the signal path of the ANR device; as well as processing the first input signal and the second input signal by at least one compensator to generate a drive signal for an acoustic transducer of the ANR device, Wherein a first gain applied to the first input signal and a second gain applied to the second input signal are selected based at least in part on a relationship between a number of sensors in the signal path and a likelihood that each of the first sensor and the second sensor will couple to the acoustic transducer, wherein the likelihood of coupling is determined based on a known position of each of the first sensor and the second sensor relative to an acoustic leakage point at an earcup or earpiece of the ANR device.

2. The method of claim 1 , wherein processing the first input signal and the second input signal to generate the drive signal comprises: combining the first input signal and the second input signal to generate a combined input signal; applying gain to the combined input signal using an amplifier; as well as The output of the amplifier is filtered by the at least one compensator to generate the drive signal for the acoustic transducer. The method of claim 2 , wherein the amplifier is part of the at least one compensator.

4. The method of claim 1 , wherein processing the first input signal and the second input signal to generate the drive signal comprises: applying the first gain to the first input signal using a first amplifier to generate a first amplified input signal; filtering the first amplified input signal by a first compensator to generate a first processed signal for the acoustic transducer of the ANR device; applying the second gain to the second input signal using a second amplifier to generate a second amplified input signal; filtering the second input signal by a second compensator to generate a second processed signal for the acoustic transducer of the ANR device; as well as The first processed signal and the second processed signal are combined to generate the drive signal for the acoustic transducer.

5. The method of claim 4, wherein the first compensator applies one or more filters to the first amplified input signal and the second compensator applies one or more filters to the second amplified input signal, the one or more filters applied to the second amplified input signal being different from the one or more filters applied to the first amplified signal.

6. The method of claim 1 , wherein processing the first input signal and the second input signal to generate the drive signal comprises: processing the first input signal by a first compensator to generate a first processed signal for the acoustic transducer of the ANR device; processing the second input signal by a second compensator to generate a second processed signal for the acoustic transducer of the ANR device; as well as The first processed signal and the second processed signal are combined to generate the drive signal for the acoustic transducer.

7. The method of claim 6, wherein the first compensator applies the first gain and one or more filters to generate the first processed signal, and the second compensator applies the second gain and one or more filters to generate the second processed signal.

8. The method of claim 1 , wherein processing the first input signal and the second input signal to generate the drive signal comprises: applying the first gain to the first input signal using a first amplifier; applying the second gain to the second input signal using a second amplifier; combining the first input signal and the second input signal to generate a combined input signal; as well as The combined input signal is filtered by the at least one compensator to generate the drive signal for the acoustic transducer.

9. The method of claim 8, wherein the first amplifier and the second amplifier are part of the at least one compensator.

10. An active noise reduction (ANR) device, the ANR device comprising: a first sensor disposed in a signal path of the device and configured to generate a first audio input signal; a second sensor disposed in the signal path of the ANR device and configured to generate a second audio input signal; and at least one compensator configured to receive and process the first audio input signal and the second audio input signal to generate a drive signal for an acoustic transducer of the ANR device, Wherein a first gain applied to the first audio input signal and a second gain applied to the second audio input signal are selected based at least in part on a relationship between a number of sensors in the signal path and a likelihood that each of the first sensor and the second sensor couples to the acoustic transducer, wherein the likelihood of coupling is determined based on a known position of each of the first sensor and the second sensor relative to an acoustic leakage point at an earcup or earpiece of the ANR device.

11. The device of claim 10, wherein the signal path is a feed-forward signal path, and each of the first sensor and the second sensor comprises a feed-forward microphone of the ANR device.

12. The device according to claim 10, comprising: a combining circuit configured to combine the first audio input signal and the second audio input signal to generate a combined input signal; and an amplifier configured to apply a gain to the combined input signal, Wherein the at least one compensator is configured to filter an output of the amplifier to generate the drive signal for the acoustic transducer.

13. The apparatus of claim 12, wherein the amplifier is part of the compensator.

14. The apparatus according to claim 10, comprising: a first compensator configured to process the first audio input signal to generate a first processed signal for the acoustic transducer of the ANR device; a second compensator configured to process the second audio input signal to generate a second processed signal for the acoustic transducer of the ANR device; and A combining circuit is configured to combine the first processed signal and the second processed signal to generate the drive signal for the acoustic transducer.

15. The apparatus of claim 14, wherein the first compensator applies the first gain and one or more filters to generate the first processed signal, and the second compensator applies the second gain and one or more filters to generate the second processed signal.

16. The apparatus according to claim 10, comprising: a first amplifier configured to apply the first gain to the first audio input signal to generate a first amplified input signal; a first compensator that filters the first amplified input signal to generate a first processed signal; a second amplifier configured to apply the second gain to the second audio input signal to generate a second amplified input signal; a second compensator that filters the second amplified input signal to generate a second processed signal; and A combining circuit is configured to combine the first processed signal and the second processed signal to generate the drive signal for the acoustic transducer.

17. The apparatus of claim 16, wherein the first compensator applies one or more filters to the first amplified input signal and the second compensator applies one or more filters to the second amplified input signal, the one or more filters applied to the second amplified input signal being different from the one or more filters applied to the first amplified signal.

18. The apparatus according to claim 10, comprising: a first amplifier configured to apply the first gain to the first audio input signal; a second amplifier configured to apply the second gain to the second audio input signal; and a combining circuit configured to combine the first audio input signal and the second audio input signal to generate a combined input signal, Wherein the at least one compensator is configured to process the combined input signal to generate the drive signal for the acoustic transducer.

19. The apparatus of claim 10, wherein the at least one compensator comprises a first filter disposed in parallel with a second filter configured to allow at least a portion of the first audio input signal to pass to the acoustic transducer in accordance with a variable gain amplifier.

20. One or more machine-readable storage devices having computer-readable instructions encoded thereon for causing one or more processing devices to perform operations comprising: Receiving a first input signal representing audio captured by a first sensor disposed in a signal path of an active noise reduction (ANR) device; receiving a second input signal representing audio captured by a second sensor disposed in the signal path of the ANR device; as well as processing the first input signal and the second input signal to generate a drive signal for an acoustic transducer of the ANR device, Wherein a first gain applied to the first input signal and a second gain applied to the second input signal are selected based at least in part on a relationship between a number of sensors in the signal path and a likelihood that each of the first sensor and the second sensor will couple to the acoustic transducer, wherein the likelihood of coupling is determined based on a known position of each of the first sensor and the second sensor relative to an acoustic leakage point at an earcup or earpiece of the ANR device.

Images