Active damping of resonant ear canal mode

Abstract

An active noise reduction (ANR) device includes an acoustic transducer, a first sensor, and a second sensor. The acoustic transducer is configured to generate output audio. The first sensor is configured to capture audio originating from an external environment of the ANR device. The second sensor is configured to generate a signal indicative of: (1) audio originating from an external environment; and (2) output audio generated by the acoustic transducer. The output audio generated by the acoustic transducer is modified based on a portion of the signal generated by the second sensor, the portion being attributable to a resonant mode of the ear canal of the user.

Description

Technical Field

[0001] This specification generally relates to active damping of audio attributable to resonant modes of a user's ear canal. Background Art

[0002] An acoustic device such as a headset may include an active noise reduction (ANR) capability that prevents at least a portion of ambient noise from reaching an eardrum of a user. The acoustic device may include one or more microphones, one or more output transducers, and a noise reduction circuit coupled to the one or more microphones and the output transducer to provide an anti-noise signal to the one or more output transducers based on a signal detected at the one or more microphones. The anti-noise signal cancels at least a portion of the ambient noise to reduce the amount of ambient noise that reaches the eardrum of the user. Summary of the invention

[0003] This document describes a method for damping audio that can be attributed to the resonant mode of the user's ear canal and an acoustic device that can implement this method. Many people's ear canals have one or more strong acoustic resonance modes (e.g., between 2000 Hz and 4000 Hz). However, when using an acoustic device such as an in-ear headphone that is inserted into the user's ear, the frequency of the resonant mode of a particular user may be significantly offset (e.g., between 3000 Hz and 10000 Hz). Compared to listening to audio without inserting the acoustic device into the user's ear, this shift in resonant frequency may cause the user to experience an unnatural listening experience when using the acoustic device. Therefore, it may be desirable to damp the audio signals at these unnatural resonant frequencies. In some specific implementations, the audio signal may correspond to audio output by one or more output transducers of the audio device and / or audio originating from an environment outside the acoustic device.

[0004] Existing acoustic devices with active noise reduction (ANR) capabilities (sometimes referred to as "ANR devices") typically use broadband control to eliminate audio signals. For example, broadband ANR control may include: capturing audio signals with one or more microphones; using an adaptive filter to generate an anti-noise signal; and driving an output transducer based on the anti-noise signal to eliminate the captured audio signal. ANR devices using broadband control can simultaneously eliminate audio over a wide frequency range, but such ANR solutions typically have an upper frequency limit of 1000Hz to 2000Hz.

[0005] At higher frequencies (e.g., 3000 Hz to 10000 Hz), the acoustic response is dominated by resonant modes. While this high frequency range has historically been out-of-band for ANR solutions, the techniques described herein use modal control to target this frequency range, actively damping audio that can be attributed to resonant modes of the user's ear canal.

[0006] Various implementations of the techniques described herein may provide one or more of the following advantages.

[0007] As previously described, unlike existing ANR solutions, the techniques described herein can damp audio at high frequencies (e.g., 3000 Hz to 10000 Hz) where the audio response may be dominated by a resonant mode. This can improve the user's listening experience by reducing noise and resulting in a more natural audio response (e.g., reducing audio peaks at unnatural resonant frequencies). In some cases, the techniques described herein can also reduce the head-to-head variability of the performance of ANR devices when used by individuals with differently shaped ear canals (and different resonant modes).

[0008] The techniques described herein may also have the advantage of being able to be implemented on hardware (e.g., microphones, output transducers, controllers, etc.) that already exists on many ANR devices. Importantly, the techniques described herein do not require an additional microphone to be inserted into the user's ear canal to measure the audio response within the user's ear canal. Instead, by using modal control and by exploiting the physical properties of resonant modes, the techniques described herein are able to reduce the response at the user's ear canal simply by damping the audio at the location of the ANR device's output transducer (sometimes referred to herein as a "driver").

[0009] In some implementations, the techniques described herein may also provide the advantage of being able to extend to multiple resonant modes and being able to be combined with existing ANR solutions (e.g., broadband control solutions) that can reduce the audio response in lower frequency regions (e.g., frequencies below 1000 Hz to 2000 Hz).

[0010] In one aspect, an active noise reduction (ANR) device includes an acoustic transducer, a first sensor, and a second sensor. The acoustic transducer is configured to generate output audio. The first sensor is configured to capture audio originating from an external environment of the ANR device. The second sensor is configured to generate a signal indicative of: (1) audio originating from the external environment; and (2) output audio generated by the acoustic transducer. The output audio generated by the acoustic transducer is modified based on a portion of the signal generated by the second sensor, the portion being attributable to a resonant mode of a user's ear canal.

[0011] Specific implementations may include examples described below and elsewhere herein. In some implementations, the portion of the signal generated by the second sensor that can be attributed to the resonant mode may include: a first sub-portion derived from the audio of the external environment originating from the ANR device; and a second sub-portion derived from the output audio generated by the acoustic transducer. In some implementations, the resonant mode may correspond to a resonant frequency between 3kHz and 10kHz. In some implementations, the output audio may be modified by feedback of the rate of the portion of the signal generated by the second sensor that can be attributed to the resonant mode. In some implementations, the output audio may be modified by adding a signal indicating the speed of the resonant mode to the output audio. In some implementations, the signal indicating the speed of the resonant mode may represent a multiple of the speed of the resonant mode. In some implementations, the signal indicating the speed of the resonant mode may represent a filtered version of the signal generated by the second sensor. In some implementations, the ANR device may be configured to be at least partially inserted into the ear of the user. In some implementations, the output audio generated by the acoustic transducer may be modified to attenuate the audio that arrives at the ear canal of the user from the external environment of the ANR device at the resonant frequency corresponding to the resonant mode. In some implementations, the output audio generated by the acoustic transducer may be modified to smooth the transfer function representing the user's ear canal at the resonant frequency corresponding to the resonant mode. In some implementations, the output audio generated by the acoustic transducer may be further modified based on a second portion of the signal generated by the second sensor, which second portion can be attributed to the second resonant mode. In some implementations, broadband noise reduction can be used at multiple frequencies below 2kHz to further modify the output audio generated by the acoustic transducer. In some implementations, the portion of the resonant mode that can be attributed to the user's ear canal can be identified by considering the user's personalized ear canal response. In some implementations, a phase-locked loop and / or a peak detection algorithm can be used to identify one or more resonant frequencies corresponding to the resonant mode. In some implementations, one or more resonant frequencies corresponding to the resonant mode can be tracked in real time.

[0012] In another aspect, a method is described. The method includes: capturing, at a first sensor of an active noise reduction (ANR) device, audio originating from an environment external to the ANR device; generating output audio at an acoustic transducer of the ANR device; and generating, at a second sensor of the ANR device, a signal indicative of: (1) audio originating from an environment external to the ANR device; and (2) output audio generated by the acoustic transducer. The method also includes: identifying a portion of the signal generated by the second sensor that is attributable to a resonant mode of an ear canal of a user of the ANR device; and modifying the output audio generated by the acoustic transducer based on the identified portion of the signal generated by the second sensor.

[0013] Specific implementations may include the examples described below and elsewhere herein. In some implementations, identifying the portion of the signal generated by the second sensor may include: deriving a first sub-portion of a resonant mode attributable to the user's ear canal from audio originating from an environment external to the ANR device; deriving a second sub-portion of a resonant mode attributable to the user's ear canal from output audio generated by the acoustic transducer; and combining the first sub-portion and the second sub-portion. In some implementations, modifying the output audio generated by the acoustic transducer may include modifying the output audio at a frequency between 3kHz and 10kHz, which corresponds to the resonant mode of the user's ear canal. In some implementations, modifying the output audio generated by the acoustic transducer may include performing rate feedback on a portion of the signal generated by the second sensor that is attributable to the resonant mode. In some implementations, modifying the output audio generated by the acoustic transducer may include: generating a signal indicating the speed of the resonant mode; and adding the signal indicating the speed of the resonant mode to the output audio. In some implementations, generating a signal indicating the speed of the resonant mode may include multiplying the speed of the resonant mode by a constant. In some implementations, generating a signal indicating the speed of the resonant mode may include filtering the portion of the signal generated by the second sensor. In some implementations, modifying the output audio generated by the acoustic transducer may include modifying the output audio to attenuate audio arriving at the ear canal of the user originating from the environment outside the ANR device at a resonant frequency corresponding to the resonant mode. In some implementations, modifying the output audio generated by the acoustic transducer may include modifying the output audio to smooth a transfer function representing the ear canal of the user at a resonant frequency corresponding to the resonant mode. In some implementations, the method may also include: identifying a second portion of a second resonant mode of the ear canal of the user in the signal generated by the second sensor; and modifying the output audio generated by the acoustic transducer based on the identified second portion of the signal generated by the second sensor. In some implementations, the method may also include modifying the output audio generated by the acoustic transducer using broadband noise reduction at multiple frequencies below 2kHz. In some implementations, identifying the portion of the resonant mode of the ear canal of the user in the signal generated by the second sensor may include taking into account the personalized ear canal response of the user. In some implementations, identifying the portion of the resonant mode of the ear canal of the user of the ANR device in the signal generated by the second sensor may include using a phase-locked loop and / or using a peak detection algorithm to identify one or more resonant frequencies corresponding to the resonant mode. In some implementations, identifying a portion of the signal generated by the second sensor that is attributable to a resonant mode of an ear canal of a user of the ANR device can also include tracking the one or more resonant frequencies in real time.

[0014] In another aspect, one or more machine-readable storage devices are featured. The one or more machine-readable storage devices have computer-readable instructions encoded thereon for causing one or more processing devices to perform operations. The operations include: capturing audio originating from an environment external to an active noise reduction (ANR) device at a first sensor of the ANR device; generating output audio at an acoustic transducer of the ANR device; and generating a signal at a second sensor of the ANR device indicating: (1) audio originating from an environment external to the ANR device; and (2) output audio generated by the acoustic transducer. The operations also include: identifying a portion of the signal generated by the second sensor that is attributable to a resonant mode of an ear canal of a user of the ANR device; and modifying the output audio generated by the acoustic transducer based on the identified portion of the signal generated by the second sensor.

[0015] Specific implementations may include the examples described below and elsewhere herein. In some implementations, identifying the portion of the signal generated by the second sensor may include: deriving a first sub-portion of a resonant mode attributable to the user's ear canal from audio originating from an environment external to the ANR device; deriving a second sub-portion of a resonant mode attributable to the user's ear canal from output audio generated by the acoustic transducer; and combining the first sub-portion and the second sub-portion. In some implementations, modifying the output audio generated by the acoustic transducer may include modifying the output audio at a frequency between 3kHz and 10kHz, which corresponds to the resonant mode of the user's ear canal. In some implementations, modifying the output audio generated by the acoustic transducer may include performing rate feedback on a portion of the signal generated by the second sensor that is attributable to the resonant mode. In some implementations, modifying the output audio generated by the acoustic transducer may include: generating a signal indicating the speed of the resonant mode; and adding the signal indicating the speed of the resonant mode to the output audio. In some implementations, generating a signal indicating the speed of the resonant mode may include multiplying the speed of the resonant mode by a constant. In some implementations, generating a signal indicating the speed of the resonant mode may include filtering the portion of the signal generated by the second sensor. In some implementations, modifying the output audio generated by the acoustic transducer may include modifying the output audio to attenuate audio arriving at the ear canal of the user originating from the environment outside the ANR device at a resonant frequency corresponding to the resonant mode. In some implementations, modifying the output audio generated by the acoustic transducer may include modifying the output audio to smooth a transfer function representing the ear canal of the user at a resonant frequency corresponding to the resonant mode. In some implementations, the operation may also include: identifying a second portion of a second resonant mode of the ear canal of the user in the signal generated by the second sensor; and modifying the output audio generated by the acoustic transducer based on the identified second portion of the signal generated by the second sensor. In some implementations, the operation may also include modifying the output audio generated by the acoustic transducer using broadband noise reduction at multiple frequencies below 2kHz. In some implementations, identifying a portion of the resonant mode of the ear canal of the user in the signal generated by the second sensor may include taking into account the personalized ear canal response of the user. In some implementations, identifying a portion of the resonant mode of the ear canal of the user of the ANR device in the signal generated by the second sensor may include using a phase-locked loop and / or using a peak detection algorithm to identify one or more resonant frequencies corresponding to the resonant mode. In some implementations, identifying a portion of the signal generated by the second sensor that is attributable to a resonant mode of an ear canal of a user of the ANR device can also include tracking the one or more resonant frequencies in real time.

[0016] Other features and advantages of the present specification will become apparent from the following description and claims. Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 An example of an in-ear active noise cancelling headphone is shown.

[0018] Figure 2 is a block diagram of a first example configuration of an acoustic device.

[0019] Figure 3 shows the corresponding Figure 2 A graph of experimental data for an acoustic device of an example configuration is shown.

[0020] Figure 4 is a block diagram of a second example configuration of an acoustic device.

[0021] Figure 5 shows the corresponding Figure 4 A graph of experimental data for an acoustic device of an example configuration is shown.

[0022] Figure 6 is a block diagram of a third example configuration of an acoustic device.

[0023] Figure 7 shows the corresponding Figure 6 A graph of simulated data for an acoustic device of the example configuration shown.

[0024] Figure 8 is a fourth example configuration representing an acoustic device Diagram of the model.

[0025] Fig. 9 shows the corresponding Figure 8 A graph of experimental data for an acoustic device of an example configuration is shown.

[0026] Fig.10 is a diagram of a hardware implementation of a portion of an acoustic device according to a fifth example configuration of the acoustic device.

[0027] Fig.11 is corresponding to Fig.10 Graphs of experimental data for a hardware implementation of an example configuration of an acoustic device are shown in FIG.

[0028] Fig.12 is a block diagram of a sixth example configuration of an acoustic device.

[0029] Fig.13 is a graph illustrating the modeling of multiple acoustic resonance modes in an acoustic response.

[0030] Fig.14 is a flow chart of a process for actively damping audio attributable to resonant modes of a user's ear canal.

[0031] Fig.15 is a diagram illustrating an example of a computing environment. DETAILED DESCRIPTION

[0032] In this document, we describe techniques that can improve the performance of acoustic devices such as active noise reduction (ANR) devices. Active noise reduction devices (such as active noise reduction headphones) are used to provide a potentially immersive listening experience by reducing the impact of ambient noise and sound. In some specific implementations, the active noise reduction device may include a feedforward microphone, a feedback microphone, an output transducer, and a noise reduction circuit that is coupled to the microphone and the output transducer to provide an anti-noise signal to the output transducer based on a signal detected at the microphone.

[0033] refer to Figure 1 The acoustic implementation of the in-ear active noise canceling headphone 100 includes a feedforward microphone 102, a feedback microphone 104, an output transducer 106 (which may also be referred to as an electroacoustic transducer or an acoustic transducer or a driver or a speaker), and a noise reduction circuit (not shown) coupled to the two microphones 102, 104 and the output transducer 106 to provide an anti-noise signal to the output transducer 106 based on signals detected at the two microphones 102, 104. Additional inputs to the circuit ( Figure 1 The in-ear active noise canceling headphone 100 may be provided with an additional audio signal (not shown), such as music or a communication signal, to be played back on the output transducer 106 independently of the noise reduction signal. Additional information about the in-ear active noise canceling headphone 100 may be found, for example, in U.S. Pat. No. 9,082,388, which is incorporated herein by reference in its entirety.

[0034] In some implementations, the feedforward microphone 102 can be disposed on an outward-facing surface of the in-ear active noise-cancelling headphone 100 and can capture audio from the environment outside the in-ear active noise-cancelling headphone 100. Therefore, the feedforward microphone 102 can sometimes be referred to as an "external microphone."

[0035] In some implementations, the feedback microphone 104 can be positioned closer to the user's ear canal than the feedforward microphone 102. The feedback microphone 104 can be configured to capture audio originating from the external environment as well as audio output by the output transducer 106. In some cases, the feedback microphone 104 may sometimes be referred to as a "system microphone."

[0036] The noise reduction circuit may include a configurable digital signal processor (DSP) that can implement various signal flow topologies and filter configurations. Examples of such digital signal processors are described in U.S. Patents 8,073,150 and 8,073,151, which are incorporated herein by reference in their entirety.

[0037] The term "headphones", which is used interchangeably with the term "earphones" herein, includes various types of personal acoustic devices, such as in-ear, circumaural, circumaural, or open-ear headphones, earphones, and hearing aids. The headphones or earphones may include an earplug or earmuff for each ear. The earplugs or earmuffs may be physically tied to each other, such as by a cord, a head-mounted bridge, or a headband or a back-of-head holding structure. In some implementations, the earplugs or earmuffs of the headphones may be connected to each other via a wireless link.

[0038] The active noise canceling headphones 100 provide a feature commonly referred to as "talking" or "monitoring", in which the external microphone 102 is used to detect external sounds that the user may want to hear. In some specific implementations, the external microphone 102, upon detecting sounds in the voice band or some other frequency band of interest, can allow the signal in the corresponding frequency band to be piped through the active noise canceling headphones 100. In some specific implementations, the active noise canceling headphones 100 allow multi-mode operation, in which in the "hear-through" mode, the active noise canceling function can be turned off or at least reduced over at least one frequency range to allow relatively broadband ambient sounds to reach the user. In some specific implementations, the active noise canceling headphones 100 allow the user to control the amount of noise and ambient sounds passing through the active noise canceling headphones 100.

[0039] In some implementations, an active noise reduction signal flow path is provided in parallel with the pass signal flow path, wherein the gain of the pass signal path can be controlled by the user. This may allow the implementation of an active noise reduction device in which the amount of ambient noise passing through may be adjusted based on user input (e.g., in discrete steps or substantially continuously) without having to turn off or reduce the active noise reduction provided by the device. In some examples, this may improve the overall user experience, for example, by avoiding any audible artifacts associated with switching between an active noise reduction mode and a pass-through mode, and / or allowing the user to control the amount of ambient noise that the user wishes to hear. This in turn may make the active noise reduction device more usable in a variety of different applications and environments, particularly in those applications and environments that require a substantially continuous balance between active noise reduction and pass-through functionality.

[0040] Various signal flow topologies may be implemented in active noise reduction devices to achieve functions such as audio equalization, feedback noise cancellation, feedforward noise cancellation, etc. Example signal flow topologies are described in U.S. Patent No. 11,062,687, which is incorporated herein by reference in its entirety. The techniques described herein may increase these functions by achieving modal control of the audio response at one or more resonant frequencies between 3000 Hz and 10000 Hz.

[0041] Figure 2 A block diagram of an example configuration 200 of an acoustic device (e.g., ANR headset 100) or a portion thereof is shown. In configuration 200, a first audio signal 202 (signal "o") is received by an external microphone (e.g., external microphone 102) and may include audio originating from an environment external to the acoustic device. For example, the audio may include noise from the environment or a human voice that the user may not wish to hear. A transfer function 206 (transfer function "Nso") represents how the audio 202 changes as it propagates from the location of the external microphone to the system microphone of the device (e.g., system microphone 104). Thus, signal 210 represents the changed audio received at the location of the system microphone that originates from the external environment.

[0042] In configuration 200, a command signal 204 (signal "d") is input to a driver or speaker (e.g., output transducer 106) of a device to drive the driver or speaker to produce a second audio signal. A transfer function 208 (transfer function "Gsd") represents how the audio output according to command signal "d" 204 changes as it propagates from the location of the driver to the system microphone of the device. Thus, signal 212 represents the changed output audio received at the location of the system microphone.

[0043] In some implementations, the "Gsd" transfer function 208 may be affected by a range of characteristics including driver design, microphone response, port design, ear canal geometry, and fit quality. Thus, the "Gsd" transfer function 208 may vary between different devices, between different users, between different usage scenarios for a single user, or even between different moments during the same usage scenario for a single user. Thus, in some implementations, it may be beneficial to measure the "Gsd" transfer function 208 in situ and / or in real time to account for these variations. Example methods of measuring the "Gsd" transfer function 208 and its decomposed subcomponents (including variations thereof) are described in U.S. Patent No. 10,937,410, which is incorporated herein by reference in its entirety.

[0044] Based on the measured "Gsd" transfer function 208 or based on the time-domain audio signal, various techniques can be used to identify and / or track one or more resonant frequencies in time (e.g., in real time). For example, in some specific implementations, one or more phase-locked loops (PLLs) can be used to identify, extract and / or track changes in resonant frequencies (e.g., corresponding to resonant noise) in the audio signal. In some specific implementations, tracking changes in resonant frequencies may include estimating the value of a derivative representing an acoustic response (e.g., relative to frequency) at a specific suspected resonant frequency. For example, this can be accomplished by measuring the frequency response at frequencies slightly below and slightly above a specific frequency. If the derivative is zero, or substantially close to zero, the resonant frequency can be considered to be correctly identified. However, if the derivative is substantially far from zero, the sign and magnitude of the derivative can be used to update the estimate of the suspected resonant frequency (e.g., based on a quadratic cost function). The process can be repeated until the resonant frequency is satisfactorily identified. In some specific implementations, other peak identification algorithms for identifying and tracking resonant frequency peaks in the frequency domain can be implemented. Once the one or more resonant frequencies have been identified and / or tracked, active damping or cancellation of audio at these resonant frequencies may be achieved using techniques such as those described in further detail herein.

[0045] The system microphone captures an audio signal 216 (signal "s"), which is a combination of signal 210 and signal 212. The captured audio signal "s" 216 may therefore include audio originating from the external environment of the acoustic device as well as audio output by the driver of the acoustic device.

[0046] Figure 3 Graphs 300A to 300D are shown, which include graphs corresponding to having Figure 2 Experimental data for an acoustic device of configuration 200 shown. Graph 300A plots audio response data corresponding to the "Nso" transfer function 206 and the "Gsd" transfer function 208. Trace 302 corresponds to the "Nso" transfer function, while trace 304 corresponds to the "Gsd" transfer function 208. Both traces 302, 304 have peaks at frequencies between 4000 Hz and 5000 Hz (indicated by dashed line 306A). These peaks are caused by resonant behavior at this frequency and correspond to resonant modes of the ear canal of a user of the acoustic device.

[0047] Graph 300B plots data representing the passive insertion gain "PIG" of the acoustic device at various frequencies. Passive insertion gain is defined as the purely passive response of the ANR device when the ANR device is worn by a user, with lower values ​​being more suitable for noise reduction applications. In graph 300B, trace 308 represents the PIG and is also observed to peak at the resonant frequency (represented by dashed line 306B in graph 300B). An important observation is that the resonant frequency 306B of the user's ear canal when the in-ear ANR device is inserted (referred to as the "blocked" state) is different from the resonant frequency 310 of the same user's ear canal when the in-ear ANR device is not inserted (referred to as the "open" state). As previously described, this shift in the resonant frequency of the user's ear canal when using the ANR device may result in an unnatural listening experience for the user. Therefore, it may be desirable to reduce the peaks in Gsd, Nso, and PIG that occur at the resonant frequency of the "blocked" state.

[0048] Generally speaking, if an audio signal received at one location is coherent with an audio signal captured at another location (e.g., by a microphone), then the signal may be cancelable at the one location. Graphs 300C and 300D plot coherence data collected from experiments conducted to determine whether resonant responses can be canceled. In these experiments, an in-ear ANR device (similar to Figure 1 The ANR device 100 shown in FIG. 1 is inserted into the ear of an artificial head that includes a microphone positioned within the ear canal to capture the audio signal “c” (“ear canal microphone”). Although in actual applications, inserting a microphone into a user's ear canal may be undesirable or impractical, for these experiments, the ear canal microphone was placed within the artificial head to determine what audio might reach the ear canal of a real user.

[0049] Graph 300C shows the coherence limits (defined as one minus the coherence) of signal "o" 202 captured by the external microphone of the ANR device and (i) signal "s" 216 captured by the system microphone and (ii) signal "c" captured by the ear canal microphone. Trace 312 indicates the coherence between signal "o" 202 and signal "s" 216. At the same time, trace 314 indicates the coherence between signal "o" 202 and signal "c". In both cases, lower values ​​of the coherence limit along the y-axis indicate higher coherence, which may be desirable for noise reduction applications. Both traces 312, 314 have a trough (represented by dashed line 306C) at the resonant frequency, indicating that at least a portion of these audio signals may be able to be eliminated.

[0050] Graph 300D shows the coherence limits of signal “c” captured by the ear canal microphone with (i) a driver-related portion of signal “s” (e.g., signal 212) and (ii) an external noise-related portion of signal “s” (e.g., signal 210). Trace 316 indicates the coherence between the driver-related portion of signal “s” and signal “c”. Meanwhile, trace 318 indicates the coherence between the external noise-related portion of signal “s” and signal “c”. Similarly, lower values ​​of the coherence limits along the y-axis indicate higher coherence, which may be desirable for noise reduction applications. Here, traces 316, 318 also have a trough at the resonant frequency (represented by dashed line 306D), indicating that at least a portion of these audio signals may be able to be eliminated.

[0051] In order to eliminate audio that can be attributed to the resonant modes of the user's ear canal, the techniques described herein implement modal control. Conventional systems for active noise reduction typically use broadband control rather than modal control, measuring the frequency response at a wide frequency range. However, such measurements do not convey internal details about the underlying physical model (such as an ear canal with one or more resonant frequencies). Instead, modal control can be implemented based on an underlying model of the internal state of the device (e.g., external noise and the output audio generated by the in-ear ANR device reaching the user's ear canal).

[0052] Figure 4 A block diagram of an example configuration 400 of an acoustic device (or a portion thereof) is shown in which the Gsd transfer function 208 is decomposed into two parallel device models 402, 404. Configuration 400 shares many similarities with configuration 200, and thus similar elements are indicated with similar reference numerals. Unlike configuration 200, in configuration 400, the Gsd transfer function 208 is decomposed into a first filter 402 ("Gsd6") corresponding to a broadband response and a second filter 404 ("Gsd1") corresponding to a first modal response (e.g., a resonant response). In some implementations, the Gsd6 device 402 can be modeled using six biquad filters, while the Gsd1 device 404 can be modeled using a single biquad filter. The Gsd6 device 402 receives an audio signal corresponding to a command signal "d" 204, and outputs a broadband portion of the audio signal (signal "s6" 406) as captured at the system microphone. On the other hand, the Gsd1 device 404 receives the audio signal corresponding to the command signal "d" 204 and outputs the resonant mode portion (e.g., the portion of the audio that can be attributed to the resonant mode) as captured at the system microphone (signal "s1" 408). In some specific implementations, the combination of signal s1 408 and signal s6 406 can be substantially similar to Figure 2212 shown in FIG. 210 , signal s6 406 , and signal s1 408 may all be combined (eg, summed) to calculate signal “s” 216 . Figure 2 Compared to configuration 200 shown in FIG. 4 , configuration 400 may have the advantage of separating out signal “ s1 ” 408 , which may enable independent damping of resonant modes (eg, by independently operating on the resonant portions of the audio originating from the driver).

[0053] As described above, in some embodiments, the Gsd transfer function 208 can be measured in situ and / or in real time (e.g., during a single use of the acoustic device) to account for differences between users and / or differences in the fit of the ANR device in the user's ear. Applying such measurements of the Gsd transfer function 208 to the configuration 400 can identify one or more high-frequency resonance peaks corresponding to the ear canal response of a particular individual, which one or more high-frequency resonance peaks can vary between users and / or between usage situations of the ANR device (e.g., between a loose fit or a tight fit of the ANR device). Such identification of personalized high-frequency resonance peaks can have the advantage of providing customized and personalized estimates of the Gsd1 device 404 and the Gsd6 device 402, resulting in more personalized noise reduction.

[0054] Figure 5 Graphs 500A, 500B are shown, which include graphs corresponding to Figure 4 Experimental acoustic response data (plotted points 502) for an acoustic device of the configuration 400 shown. Graph 500A plots the magnitude of the acoustic response of the Gsd transfer function 208 at various frequencies, while graph 500B plots the phase of the acoustic response. Trace 504, which is fitted to plotted points 502, therefore represents an estimate of the overall Gsd transfer function 208. Meanwhile, trace 506 represents an estimate of the Gsd1 filter 404, and trace 508 represents an estimate of the Gsd6 filter 402. As expected, the estimated response of the Gsd1 filter 404 has a single peak at the resonant frequency (e.g., approximately 5000 Hz) because it is the only resonant response. In addition, the estimated response of the Gsd1 filter 404 (resonant mode response) and the estimated response of the Gsd6 filter 402 (wideband response) add up to the total response of the Gsd transfer function 208, as expected based on the configuration 400.

[0055] Reference now Figure 6, a block diagram of another example configuration 600 of an acoustic device (or a portion thereof) is shown. Configuration 600 shares many similarities with configuration 400, and thus like elements are indicated with like reference numerals. However, in this configuration, the Nso transfer function 206 is also decomposed into two parallel device models 602, 604. Similar to the Gsd transfer function, the Nso transfer function 206 is separated into a first filter 602 ("Nso6") corresponding to a broadband response and a second filter 604 ("Nso1") corresponding to a first modal response (e.g., a resonant modal response). In some implementations, the Nso6 device 602 can be modeled using six biquad filters, while the Nso1 device 604 can be modeled using a single biquad filter. The Nso6 device 602 receives the signal "o" 202 and outputs a broadband portion of the signal "o" as captured at the system microphone (signal 606). On the other hand, Nso1 device 604 receives signal "o" 202 and outputs the resonant mode portion (e.g., the portion of the audio that can be attributed to the resonant mode) as captured at the system microphone (signal 608). In some implementations, the combination of signal 608 and signal 606 can be substantially similar to Figure 2 and Figure 4 The signal 210 is shown in FIG.

[0056] Another difference of configuration 600 compared to configuration 400 is that signal "s6" (audio attributable to a wideband response) and signal "s1" (audio attributable to a resonant response) now include contributions from both the driver output (e.g., the audio output corresponding to the driver command signal "d" 204) and the external noise (e.g., signal "o" 202) because both transfer functions 206, 208 are separated into parallel devices. In configuration 600, signal "s6" 612 includes a combination (e.g., a sum) of a wideband signal 606 originating from the external environment and a wideband signal 406 originating from the driver. At the same time, signal "s1" 610 includes a combination (e.g., a sum) of a resonant signal 608 originating from the external environment and a resonant signal 408 originating from the driver. The combination (e.g., a sum) of signal "s1" 610 and signal "s6" can produce a complete signal "s" 216 captured at the system microphone.

[0057] In configuration 600, isolating signal "s1" 610 (the audio that can be attributed to the resonant response) can achieve independent damping of the resonant mode. To this end, assuming that signal "s1" can be estimated, configuration 600 can include a damping feedback loop having a damping filter 614 that acts on signal "s1" 610 to actively damp the audio that can be attributed to the resonant mode. The damping loop can perform rate feedback on signal "s1" 610, thereby effectively counteracting the velocity of the resonant mode. For example, in some specific implementations, the damping filter 614 can be a single biquad low pass filter that multiplies the velocity of the resonant mode by a constant factor. The resulting signal can then be combined with other components such as an external signal "d ext ” 616 are combined (e.g., summed) to generate a driver command signal “d” 204, which is fed back to the driver to adjust the audio output of the driver.

[0058] Figure 7 Graphs 700A, 700B are shown, which include graphs corresponding to Figure 6 The simulation data of the acoustic device of the configuration 600 shown in , demonstrates the potential improvement to the ANR performance if the signal "s1" can be accurately estimated. The curve graph 700A plots the undamped response of the transfer function Nso (trace 702) and the modal damped response of the transfer function Nso (trace 704). In theory, the configuration 600 should produce a damped response of the transfer function Nso, which can be expressed as:

[0059]

[0060] and should only affect resonant modes. As expected, in graph 700A, the peak of the undamped trace 702 at the resonant frequency (e.g., between 4000 Hz and 5000 Hz) is significantly reduced in the damped trace 704, while minimal effects are observed at other frequencies. This example demonstrates the ability of an acoustic device having configuration 600 to specifically target and reduce external noise that can be attributed to the resonant modes of the user's ear canal.

[0061] Graph 700B plots the undamped response of the transfer function Gsd (trace 706) and the modally damped response of the transfer function Gsd (trace 708). In theory, the configuration 600 should produce a damped response of the transfer function Gsd, which can be expressed as:

[0062]

[0063] and should only affect resonant modes. As expected, in graph 700B, the peak of the undamped trace 706 at the resonant frequency (e.g., between 4000 Hz and 5000 Hz) is significantly reduced in the damped trace 708, while minimal effects are observed at other frequencies. This example demonstrates the ability of an acoustic device having configuration 600 (e.g., by smoothing the frequency response of the transfer function Gsd) to specifically target and reduce unnatural peaks in the driver output that can be attributed to resonant modes of the user's ear canal.

[0064] Reference now Figure 8 , showing A diagram of a model representing another example configuration 800 of an acoustic device (or a portion thereof). Elements of configuration 800 that are similar to elements of previously described configurations (eg, configurations 200, 400, 600) are indicated with like reference numerals.

[0065] Similar to other configurations of acoustic devices, configuration 800 includes a device 802 that receives a signal "o" 202 and a signal "d" 204 as inputs. Device 802 receives signals 202, 204 and simulates an output signal "s" 216 captured at a system microphone of the acoustic device. In some implementations, device 802 may correspond to Figure 2 Configuration 200 shown in .

[0066] The output signal "s" 216 is fed to the state estimator 804, which receives a signal 812 representing the difference between the output signal "s" 216 and the estimated resonant response portion of the output signal "s" (e.g., signal "s1" 610). In some implementations, the signal 812 may correspond to the difference 806 between the signal "s" 216 and the signal "s1" 610 after being scaled by the amplifier 808 and delayed by the delay block 810.

[0067] The state estimator 804 also receives as inputs the signal "o" 202 and the signal "d" 204, and based on these inputs (e.g., the signals 202, 204, 812) estimates the resonant response signal (signal "s1" 610) and its modal velocity 814. As in configuration 600, in configuration 800, the modal velocity 814 may be fed through a damping loop, where the resulting signal is fed back to the driver (e.g., by comparing it with the signal "d ext ” 616 is summed to generate a command signal “d” 204). Figure 8As shown, the damping loop may include a damping filter 816 (e.g., a biquad filter), a delay block 818, and an amplifier 820. In some implementations, the resonant response signal (signal "s1" 610) may be fed directly to the damping loop (e.g., instead of the modal velocities 814), and the damping filter 816 of the damping loop may be configured to take the derivative of the signal "s1" 610 to obtain the modal velocities.

[0068] Fig. 9 Graphs 900A, 900B are shown, which include graphs corresponding to Figure 8 800. Graph 900A plots the magnitude of various acoustic responses at different frequencies, while graph 900B plots the phase of the same acoustic responses. Trace 902 corresponds to the response of the complete undamped Gsd transfer function (e.g., Gsd transfer function 208, which is included in device 802 in configuration 800). Trace 906 corresponds to the simulated damped response of the complete Gsd model, and trace 904 corresponds to the laboratory measured damped response of the complete Gsd model.

[0069] Trace 902, corresponding to the undamped Gsd transfer function, demonstrates a significant peak at frequencies between 5000 Hz and 6000 Hz that can be attributed to the resonant mode of the user's ear canal. However, as shown in traces 904 and 906 (which are very similar to each other), after performing active damping on the resonant mode using modal control, both the simulated damped response and the laboratory measured response demonstrate a significant reduction in this peak, effectively smoothing the response at the resonant frequencies.

[0070] Reference now Fig.10 , a diagram illustrating a hardware implementation of a portion of an acoustic device (e.g., a processor of the acoustic device running software to implement an estimator and a damping controller). The hardware implementation is shown having a configuration 1000. Elements of the configuration 1000 that are similar to elements of previously described configurations of the acoustic device (e.g., configurations 200, 400, 600, 800) are indicated with like reference numerals.

[0071] In configuration 1000, signal "o" 202 (captured by an external microphone of the acoustic device) is fed through an Nso1 filter 604 to produce a signal 608 (representing a portion of the external noise captured at the system microphone that can be attributed to the resonant mode). At the same time, the signal "s" 216 captured at the system microphone is delayed and combined with an estimate of the signal "s1" 610 (representing a portion of the total audio captured at the system microphone that can be attributed to the resonant mode) at the subtractor 1002. The output of the subtractor 1002 is a difference signal "s-s1" 806, which is amplified by an amplifier 808, combined with the driver command signal "d" 204 at the adder 1004, and fed through the Gsd1 filter 404 to produce the signal 408. As previously described, the signal 408 represents a portion of the audio output by the driver captured at the system microphone that can be attributed to the resonant mode. At the adder 1006, the signals 408 and 608 are combined to calculate an updated estimate of the signal "s1" 610. In addition to being fed back to the adder 1002, the signal "s1" 610 is input to a damping filter 816 (which may be configured to obtain the modal velocity of the signal "s1" 610) and scaled by an amplifier 820. The resulting signal is combined with the external signal "d_ext" 616 at the mixer 1008, and the combined signal is clipped at the clipping module 1010. The resulting signal is the updated driver command signal "d" 204 that is fed back to the adder 1004.

[0072] Fig.11 100 is a graph 1100, which includes experimental acoustic response data corresponding to a hardware implementation of an acoustic device, the acoustic device including components corresponding to configuration 1000. Trace 1102 corresponds to the PIG of the acoustic device, which exhibits a peak of a resonant mode corresponding to the ear canal of a user between 3000 Hz and 4000 Hz. Trace 1104 corresponds to the acoustic response of the same device after active damping of the resonant mode is implemented according to configuration 1000. As shown in graph 1100, trace 1004 significantly reduces the acoustic response at the resonant frequency. In addition, the level of reduction can be tuned by adjusting the gain of the damping loop (e.g., by adjusting the gain value of amplifier 820). Trace 1106 shows the acoustic response of the device after the damping loop gain is doubled compared to the value that produces trace 1004, and as expected, trace 1106 exhibits a greater reduction in the acoustic response at the resonant frequency.

[0073] Reference now Fig.12, a block diagram of another example configuration 1200 of an acoustic device (or a portion thereof) is shown. Configuration 1200 is nearly identical to configuration 600, and thus like elements are indicated with like reference numerals. However, configuration 1200 differs from configuration 600 in that it includes an additional feedback loop in which a signal "s" 216 captured at the system microphone is fed through a feedback filter 1202, and the resulting signal is summed with a driver signal "d" 204. While some of the configurations previously described in this document (e.g., configurations 600, 800, 1000) include only a single damping loop to implement modal control of a particular resonant mode, configuration 1200 demonstrates that the modal control techniques described herein can be easily combined with other ANR solutions (e.g., broadband control based on feedback signals and feedforward signals) in a single acoustic device.

[0074] In some implementations, the techniques described herein can be further extended to include modal control of multiple resonant modes simultaneously (eg, using damping feedback loops). Fig.13 A graph 1300 is shown, demonstrating that the model fitting method can successfully decompose the complete undamped transfer function Gsd (e.g., Gsd transfer function 208) into a broadband response 1302 and three separate resonant responses 1304A to 1304C. This can be understood as Figure 5 Thus, those skilled in the art will appreciate that the present disclosure enables various other configurations for acoustic devices that implement modal control to reduce acoustic responses corresponding to multiple resonant modes.

[0075] Although the damping loop described above has been described as a feedback loop, in some specific implementations, the feedback damping loop described herein may be equivalently implemented as a combination of a feedback filter and a feedforward filter. Fig.10 , the equivalent feedback filter and feedforward filter can have the following transfer functions respectively:

[0076]

[0077] If we assume that the signal "d ext "1010 to achieve broadband feedback and feedforward control:

[0078] d ext =K fb s+K ff o

[0079] In some implementations, using these equivalent feedback filters and feedforward filters can have the advantage of being more easily integrated with existing ANR solutions implemented on acoustic devices.

[0080] Fig.14 An example process 1400 for actively damping audio that can be attributed to a resonant mode of a user's ear canal is illustrated. In some implementations, the operations of process 1400 can be performed by an acoustic device such as Figure 1 The in-ear ANR device 100 shown in FIG. 1 is performed.

[0081] The operation of process 1400 includes capturing, at a first sensor of an active noise reduction (ANR) device, audio originating from an environment external to the ANR device. In some implementations, the first sensor may correspond to an external microphone (e.g., external microphone 102) of the ANR device. The audio originating from an environment external to the ANR device may correspond to signal "o" 202.

[0082] The operations of process 1400 also include generating output audio at an acoustic transducer of the ANR device. The acoustic transducer may correspond to Figure 1 The output transducer 106 shown in , or may be another speaker or driver of an acoustic device described throughout this disclosure. The generated output audio may correspond to a signal “d” 204 ​​.

[0083] The operation of process 1400 also includes generating a signal at a second sensor of the ANR device indicating: (1) audio originating from an environment external to the ANR device; and (2) output audio generated by the acoustic transducer. In some implementations, the second sensor may correspond to a system microphone of the acoustic device (e.g., system microphone 104), and the generated signal may correspond to audio captured by the system microphone (e.g., signal "s" 216).

[0084] The operation of process 1400 also includes identifying a portion of the signal generated by the second sensor that is attributable to a resonant mode of the ear canal of a user of the ANR device. For example, the portion of the signal generated by the second sensor that is attributable to the resonant mode may correspond to the signal "s-1" 610 described above. Identifying the portion of the signal generated by the second sensor may include deriving a first sub-portion (e.g., signal 608) of the resonant mode attributable to the user's ear canal from audio originating from an environment external to the ANR device. Identifying the portion of the signal generated by the second sensor may also include deriving a second sub-portion (e.g., signal 408) of the resonant mode attributable to the user's ear canal from output audio generated by the acoustic transducer. Identifying the portion of the signal generated by the second sensor may also include combining the first sub-portion with the second sub-portion (e.g., by adding them).

[0085] The operation of process 1400 also includes modifying the output audio generated by the acoustic transducer based on the identified portion of the signal generated by the second sensor. Modifying the output audio may include modifying the output audio at a frequency between 3kHz and 10kHz. For example, the frequency may correspond to a resonant mode of the user's ear canal. Modifying the output audio may also include generating a signal indicating the speed of the resonant mode and adding the signal to the output audio. Generating a signal indicating the speed of the resonant mode may include multiplying the speed of the resonant mode by a constant. Generating a signal indicating the speed of the resonant mode may also include filtering a portion of the signal generated by the second sensor (e.g., signal "s1" 610) (e.g., using filter 816). In some specific implementations, modifying the output audio may include modifying the output audio to smooth a transfer function representing the user's ear canal at a resonant frequency corresponding to the resonant mode.

[0086] Additional operations of process 1400 may include the following operations. In some implementations, process 1400 may include identifying a second portion of a signal generated by a second sensor that is attributable to a second resonant mode of an ear canal of a user. In such implementations, process 1400 may also include modifying the output audio generated by the acoustic transducer based on the identified second portion. In some implementations, process 1400 may include modifying the output audio generated by the acoustic transducer using broadband noise reduction at multiple frequencies below 2 kHz.

[0087] Fig.15 Examples of computing devices 1500 and mobile computing devices 1550 that are employed to perform specific implementations of the present disclosure are shown. Computing device 1500 is intended to represent various forms of digital computers, such as laptops, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframes, and other appropriate computers. Mobile computing device 1550 is intended to represent various forms of mobile devices, such as personal digital assistants, cellular phones, smart phones, AR devices, and other similar computing devices. The components shown here, their connections and relationships, and their functions are intended to be examples only and are not intended to be limiting. Computing device 1500 and / or mobile computing device 1550 can form at least a portion of an acoustic device such as an in-ear ANR device 100.

[0088] The computing device 1500 includes a processor 1502, a memory 1504, a storage device 1506, a high-speed interface 1508, and a low-speed interface 1512. In some implementations, the high-speed interface 1508 is connected to the memory 1504 and a plurality of high-speed expansion ports 1510. In some implementations, the low-speed interface 1512 is connected to the low-speed expansion port 1514 and the storage device 1504. Each of the processor 1502, the memory 1504, the storage device 1506, the high-speed interface 1508, the high-speed expansion port 1510, and the low-speed interface 1512 is interconnected using various buses and may be mounted on a common motherboard or in other suitable ways. The processor 1502 may process instructions for execution within the computing device 1500, including instructions stored in the memory 1504 and / or on the storage device 1506, to display graphical information of a graphical user interface (GUI) on an external input / output device such as a display 1516 coupled to the high-speed interface 1508. In other specific implementations, multiple processors and / or multiple buses may be used appropriately with multiple memories and memory types. In addition, multiple computing devices may be connected, with each device providing portions of the necessary operations (e.g., as a server group, a group of blade servers, or a multi-processor system).

[0089] The memory 1504 stores information within the computing device 1500. In some implementations, the memory 1504 is one or more volatile memory units. In some implementations, the memory 1504 is one or more non-volatile memory units. The memory 1504 may also be another form of computer-readable medium, such as a magnetic disk or optical disk.

[0090] Storage device 1506 can provide mass storage for computing device 1500. In some specific implementations, storage device 1506 can be or include computer readable media, such as floppy disk devices, hard disk devices, optical disk devices, tape devices, flash memory, or other similar solid-state memory devices, or device arrays, including devices in storage area networks or other configurations. Instructions can be stored in information carriers. Instructions execute one or more methods, such as those described above, when executed by one or more processing devices (such as processor 1502). Instructions can also be stored by one or more storage devices, such as computer readable or machine readable media, such as memory 1504, storage device 1506, or memory on processor 1502.

[0091] The high-speed interface 1508 manages bandwidth-intensive operations for the computing device 1500, while the low-speed interface 1512 manages lower bandwidth-intensive operations. This functional allocation is only an example. In some specific implementations, the high-speed interface 1508 is coupled to the memory 1504, the display 1516 (e.g., through a graphics processor or an accelerator), and is coupled to a high-speed expansion port 1510 that can accept various expansion cards. In this specific implementation, the low-speed interface 1512 is coupled to the storage device 1506 and the low-speed expansion port 1514. The low-speed expansion port 1514, which can include various communication ports (e.g., universal serial bus (USB), Bluetooth, Ethernet, wireless Ethernet), can be coupled to one or more input / output devices. Such input / output devices can include scanners, printing devices, or keyboards or mice. The input / output device can also be coupled to the low-speed expansion port 1514 through a network adapter. Such network input / output devices can include, for example, switches or routers.

[0092] The computing device 1500 may be implemented in a variety of different forms, such as Fig.15 As shown. For example, it can be implemented as a standard server 1520, or multiple times in a group of such servers. In addition, it can be implemented in a personal computer such as a laptop computer 1522. It can also be implemented as part of a rack server system 1524. Alternatively, components from computing device 1500 can be combined with other components in a mobile device (such as mobile computing device 1550). Each of such devices can contain one or more of computing device 1500 and mobile computing device 1550, and the entire system can be composed of multiple computing devices that communicate with each other.

[0093] The mobile computing device 1550 includes: a processor 1552; a memory 1564; an input / output device such as a display 1554; a communication interface 1566; and a transceiver 1568; as well as other components. The mobile computing device 1550 may also be provided with a storage device, such as a micro drive or other device, to provide additional storage. Each of the processor 1552, the memory 1564, the display 1554, the communication interface 1566, and the transceiver 1568 are interconnected using various buses, and several of these components may be mounted on a common motherboard or otherwise as appropriate. In some implementations, the mobile computing device 1550 may include a camera device.

[0094] The processor 1552 can execute instructions within the mobile computing device 1550, including instructions stored in the memory 1564. The processor 1552 can be implemented as a chipset including multiple independent analog processors and digital processors. For example, the processor 1552 can be a complex instruction set computer (CISC) processor, a reduced instruction set computer (RISC) processor, or a minimum instruction set computer (MISC) processor. The processor 1552 can provide, for example, coordination of other components of the mobile computing device 1550, such as control of a user interface (UI), applications running on the mobile computing device 1550, and / or wireless communications of the mobile computing device 1550.

[0095] The processor 1552 can communicate with the user through the control interface 1558 and the display interface 1556 coupled to the display 1554. The display 1554 can be, for example, a thin film transistor liquid crystal display (TFT) display or an organic light emitting diode (OLED) display or other suitable display technology. The display interface 1556 may include appropriate circuits for driving the display 1554 to present graphical information and other information to the user. The control interface 1558 can receive commands from the user and convert them for submission to the processor 1552. In addition, the external interface 1562 can provide communication with the processor 1552 to enable near-area communication of the mobile computing device 1550 with other devices. The external interface 1562 can provide, for example, wired communication in some specific implementations, or wireless communication in other specific implementations, and multiple interfaces can also be used.

[0096] The memory 1564 stores information within the mobile computing device 1550. The memory 1564 may be implemented as one or more of one or more computer-readable media, one or more volatile memory units, or one or more non-volatile memory units. An expansion memory 1574 may also be provided and connected to the mobile computing device 1550 via an expansion interface 1572, which may include, for example, a single in-line memory module (SIMM) card interface. The expansion memory 1574 may provide additional storage space for the mobile computing device 1550, or may also store applications or other information for the mobile computing device 1550. Specifically, the expansion memory 1574 may include instructions to perform or supplement the above-mentioned processes, and may also include security information. Thus, for example, the expansion memory 1574 may be provided as a security module for the mobile computing device 1550, and may be programmed with instructions that allow the mobile computing device 1550 to be used securely. In addition, security applications and additional information may be provided via a SIMM card, such as placing identification information on the SIMM card in an unbreakable manner.

[0097] As discussed below, the memory may include, for example, flash memory and / or non-volatile random access memory (NVRAM). In some implementations, the instructions are stored in an information carrier. The instructions, when executed by one or more processing devices (such as processor 1552), perform one or more methods, such as those described above. The instructions may also be stored by one or more storage devices, such as one or more computer-readable or machine-readable media, such as memory 1564, expansion memory 1574, or memory on processor 1552. In some implementations, the instructions may be received in a propagated signal (such as through transceiver 1568 or external interface 1562).

[0098] The mobile computing device 1550 can communicate wirelessly through the communication interface 1566, which may include digital signal processing circuits where necessary. The communication interface 1566 can provide communication under various modes or protocols, such as global system for mobile communications (GSM) voice calls, short message service (SMS), enhanced message service (EMS), multimedia message service (MMS) message transmission, code division multiple access (CDMA), time division multiple access (TDMA), personal digital cellular (PDC), wideband code division multiple access (WCDMA), CDMA2000, general packet radio service (GPRS). Such communication can be carried out, for example, using radio frequency through the transceiver 1568. In addition, short-range communication such as using Bluetooth or Wi-Fi may occur. In addition, the global positioning system (GPS) receiver module 1570 can provide additional navigation-related and location-related wireless data to the mobile computing device 1550, which can be used appropriately by applications running on the mobile computing device 1550.

[0099] Mobile computing device 1550 may also communicate audibly using audio codec 1560, which may receive verbal information from a user and convert it into usable digital information. Audio codec 1560 may similarly produce audible sounds to the user, such as through a speaker (e.g., in a handset of mobile computing device 1550). Such sounds may include sounds from voice phone calls, may include recorded sounds (e.g., voice messages, music files, etc.), and may also include sounds produced by applications operating on mobile computing device 1550.

[0100] Mobile computing device 1550 may be implemented in a variety of different forms, such as Fig.15 As shown. For example, it can be implemented as a telephone device 1580, a personal digital assistant 1582, and a tablet device (not shown). The mobile computing device 1550 can also be implemented as a component of a smart phone, an AR device, or other similar mobile devices.

[0101] The computing device 1500 may be implemented as an acoustic device (such as the one described above with respect to Figure 1 Part of the in-ear ANR device described.

[0102] Computing device 1500 and / or 1550 may also include a USB flash drive. The USB flash drive may store an operating system and other applications. The USB flash drive may include input / output components such as a wireless transmitter or a USB connector that may be inserted into a USB port of another computing device.

[0103] Other embodiments and applications not specifically described herein are also within the scope of the following claims. Elements of different implementations described herein can be combined to form other embodiments.

Claims

1. An active noise reduction (ANR) device, the active noise reduction (ANR) device comprising: an acoustic transducer configured to generate output audio; a first sensor configured to capture audio originating from an external environment of the ANR device; and a second sensor configured to generate a signal indicative of: (1) the audio from the external environment; and (2) the output audio generated by the acoustic transducer, Wherein the output audio generated by the acoustic transducer is modified based on a portion of the signal generated by the second sensor, the portion being attributable to a resonant mode of an ear canal of a user.

2. The ANR device of claim 1 , wherein the portion of the signal generated by the second sensor that is attributable to the resonant mode comprises: a first sub-portion derived from the audio of the external environment originating from the ANR device; and A second sub-portion is derived from the output audio generated by the acoustic transducer.

3. The ANR device according to claim 1, wherein the resonance mode corresponds to a resonance frequency between 3 kHz and 10 kHz.

4. The ANR device of claim 1, wherein the output audio is modified by velocity feedback of the portion of the signal generated by the second sensor attributable to the resonant mode.

5. The ANR device of claim 1, wherein the output audio is modified by adding a signal indicative of a speed of the resonant mode to the output audio. 6 . The ANR device of claim 5 , wherein the signal indicative of the speed of the resonant mode represents a multiple of the speed of the resonant mode.

7. The ANR device of claim 5, wherein the signal indicative of the speed of the resonant mode represents a filtered version of the signal generated by the second sensor.

8. The ANR device of claim 1, wherein the ANR device is configured to be at least partially inserted into an ear of the user.

9. The ANR device of claim 1, wherein the output audio generated by the acoustic transducer is modified to attenuate the audio originating from the external environment of the ANR device that reaches the ear canal of the user at a resonant frequency corresponding to the resonant mode.

10. The ANR device of claim 1, wherein the output audio generated by the acoustic transducer is modified to smooth a transfer function representative of the user's ear canal at a resonant frequency corresponding to the resonant mode.

11. The ANR device of claim 1 , wherein the output audio generated by the acoustic transducer is further modified based on a second portion of the signal generated by the second sensor, the second portion being attributable to a second resonant mode.

12. The ANR device of claim 1, wherein the output audio generated by the acoustic transducer is further modified using broadband noise reduction at multiple frequencies below 2 kHz.

13. The ANR device of claim 1, wherein the portion of the resonant mode attributable to an ear canal of a user is identified by taking into account an individualized ear canal response of the user.

14. The ANR device of claim 1, wherein one or more resonant frequencies corresponding to the resonant mode are identified using a phase locked loop and / or using a peak detection algorithm.

15. The ANR device of claim 1, wherein one or more resonant frequencies corresponding to the resonant mode are tracked in real time.

16. A method comprising: capturing, at a first sensor of an active noise reduction (ANR) device, audio originating from an environment external to the ANR device; generating output audio at an acoustic transducer of the ANR device; A signal is generated at a second sensor of the ANR device indicative of: (1) the audio originating from the environment external to the ANR device; and (2) the output audio generated by the acoustic transducer; identifying a portion of the signal generated by the second sensor attributable to a resonant mode of an ear canal of a user of the ANR device; as well as The output audio generated by the acoustic transducer is modified based on the identified portion of the signal generated by the second sensor.

17. The method of claim 16, wherein identifying the portion of the signal generated by the second sensor comprises: deriving a first sub-portion of the resonant mode attributable to the ear canal of the user from the audio originating from the environment external to the ANR device; deriving a second sub-portion of the resonant mode attributable to the ear canal of the user from the output audio generated by the acoustic transducer; as well as The first sub-portion and the second sub-portion are combined.

18. The method of claim 16, wherein modifying the output audio generated by the acoustic transducer comprises modifying the output audio at a frequency between 3 kHz and 10 kHz, the frequency corresponding to the resonant mode of the ear canal of the user.

19. The method of claim 16, wherein modifying the output audio generated by the acoustic transducer comprises performing rate feedback on the portion of the signal generated by the second transducer attributable to the resonant mode.

20. The method of claim 16, wherein modifying the output audio generated by the acoustic transducer comprises: generating a signal indicative of a speed of the resonant mode; as well as The signal indicative of the speed of the resonant mode is added to the output audio.

21. The method of claim 20, wherein generating the signal indicative of the speed of the resonant mode comprises multiplying the speed of the resonant mode by a constant.

22. The method of claim 20, wherein generating the signal indicative of the velocity of the resonant mode comprises filtering the portion of the signal generated by the second sensor.

23. A method according to claim 16, wherein modifying the output audio generated by the acoustic transducer includes modifying the output audio to attenuate the audio arriving at the ear canal of the user originating from the environment outside the ANR device at a resonant frequency corresponding to the resonant mode.

24. The method of claim 16, wherein modifying the output audio generated by the acoustic transducer comprises modifying the output audio to smooth a transfer function representative of the user's ear canal at a resonant frequency corresponding to the resonant mode.

25. The method according to claim 16, further comprising: identifying a second portion of the signal generated by the second sensor attributable to a second resonant mode of the ear canal of the user; as well as The output audio generated by the acoustic transducer is modified based on the identified second portion of the signal generated by the second sensor.

26. The method of claim 16, further comprising modifying the output audio generated by the acoustic transducer using broadband noise reduction at a plurality of frequencies below 2 kHz.

27. The method of claim 16, wherein identifying the portion of the signal generated by the second sensor attributable to the resonant mode of the ear canal of the user comprises: The user's individual ear canal response is taken into account.

28. The method of claim 16, wherein identifying the portion of the signal generated by the second sensor attributable to the resonant mode of the ear canal of the user of the ANR device comprises: One or more resonant frequencies corresponding to the resonant mode are identified using a phase locked loop and / or using a peak detection algorithm.

29. The method of claim 28, wherein identifying the portion of the signal generated by the second sensor attributable to the resonant mode of the ear canal of the user of the ANR device further comprises: The one or more resonant frequencies are tracked in real time.

30. One or more machine-readable storage devices having computer-readable instructions encoded thereon for causing one or more processing devices to perform operations comprising: capturing, at a first sensor of an active noise reduction (ANR) device, audio originating from an environment external to the ANR device; generating output audio at an acoustic transducer of the ANR device; A signal is generated at a second sensor of the ANR device indicative of: (1) the audio originating from the environment external to the ANR device; and (2) the output audio generated by the acoustic transducer; identifying a portion of the signal generated by the second sensor attributable to a resonant mode of an ear canal of a user of the ANR device; as well as The output audio generated by the acoustic transducer is modified based on the identified portion of the signal generated by the second sensor.

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