Active attenuation of resonant canal modes

Abstract

The active noise reduction (ANR) device includes an acoustic transducer, a first sensor, and a second sensor. The acoustic transducer is configured to generate an output audible sound. The first sensor is configured to capture audible sound originating from an environment external to the ANR device. The second sensor is configured to generate a signal indicative of (1) the audible sound originating from the environment and (2) the output audible sound generated by the acoustic transducer. The output audible sound generated by the acoustic transducer is modified based in part on the signal generated by the second sensor, the portion resulting from a resonant mode of the user's ear canal.

Description

[Technical Field]

[0001] This description generally relates to active attenuation of audio due to resonant modes in a user's ear canal. [Background technology]

[0002] An acoustic device, such as headphones, may include an active noise reduction (ANR) feature that prevents at least a portion of ambient noise from reaching a user's eardrums. 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 transducers and configured to provide a noise reduction signal to the one or more output transducers based on signals detected at the one or more microphones. The noise reduction signal cancels at least a portion of the ambient noise to reduce the amount of ambient noise that reaches the user's eardrums. Summary of the Invention

[0003] This document describes a method for attenuating audible sounds resulting from resonant modes in a user's ear canal, and an acoustic device capable of implementing such a method. Many human ear canals have one or more strong acoustic resonant modes (e.g., between 2000 Hz and 4000 Hz). However, when using an acoustic device, such as in-ear headphones, inserted in a user's ear, the frequency of a particular user's resonant mode may shift substantially (e.g., between 3000 Hz and 10,000 Hz). This shift in resonant frequency may result in the user experiencing an unnatural listening experience when using the acoustic device compared to hearing audible sounds without the acoustic device inserted in the user's ear. Therefore, it may be desirable to attenuate audible sound signals at these unnatural resonant frequencies. In some implementations, the audible sound signals may correspond to audible sound output by one or more output transducers of the audio device and / or audible sounds originating from the environment external to the acoustic device.

[0004] Existing acoustic devices with active noise reduction (ANR) capabilities (sometimes referred to as "ANR devices") often use broadband control to cancel audible signals. For example, broadband ANR control may involve capturing an audible signal with one or more microphones, generating an anti-noise signal using an adaptive filter, and driving an output transducer based on the anti-noise signal to cancel the captured audible signal. While ANR devices using broadband control can simultaneously cancel audible sounds over a wide range of frequencies, such ANR solutions typically have an upper frequency limit of 1,000 to 2,000 Hz.

[0005] At higher frequencies (e.g., 3000-10,000 Hz), the acoustic response is dominated by resonant modes. This high-frequency range has historically been out of range of ANR solutions, but the techniques described herein use mode control to target this frequency range and actively attenuate audible sounds resulting from resonant modes in 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 mentioned, unlike existing ANR solutions, the technology described herein can attenuate audible sounds at high frequencies (e.g., 3000-10,000 Hz), where the audible sound response can be dominated by resonant modes. This can improve the user's listening experience by reducing noise and resulting in a more natural sound response (e.g., reducing audio peaks at unnatural resonant frequencies). In some cases, the technology described herein can also reduce head-to-head variability in ANR device performance 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 implementable with hardware already present in many ANR devices (e.g., microphones, output transducers, controllers, etc.). Importantly, the techniques described herein do not require the insertion of an additional microphone into a user's ear canal to measure the audio response therein. Rather, by using mode control and taking full advantage of the physics of resonant modes, the techniques described herein can reduce the response in a user's ear canal by simply attenuating audible sound at the location of the ANR device's output transducer (sometimes referred to herein as the "driver").

[0009] In some implementations, the techniques described herein can also offer the advantage of being scalable to multiple resonant modes and being able to be combined with existing ANR solutions (e.g., broadband control solutions) that can reduce audio response in the lower frequency regime (e.g., frequencies below 1,000-2,000 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 an output audible sound. The first sensor is configured to capture audible sound originating from an environment external to the ANR device. The second sensor is configured to generate signals indicative of (1) the audible sound originating from the environment and (2) the output audible sound generated by the acoustic transducer. The output audible sound 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] Implementations may include examples described below and elsewhere herein. In some implementations, the portion of the signal generated by the second sensor attributable to the resonant mode may include a first sub-portion derived from an audible sound originating in an environment external to the ANR device and a second sub-portion derived from the output audible sound generated by the acoustic transducer. In some implementations, the resonant mode may correspond to a resonant frequency between 3 kHz and 10 kHz. In some implementations, the output audio may be modified by rate feedback on the portion of the signal generated by the second sensor attributable to the resonant mode. In some implementations, the output audible sound may be modified by adding a signal indicative of the velocity of the resonant mode to the output audible sound. In some implementations, the signal indicative of the velocity of the resonant mode may represent a multiple of the velocity of the resonant mode. In some implementations, the signal indicative of the velocity 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 a user's ear. In some implementations, the output audible sound generated by the acoustic transducer may be modified to attenuate audible sound originating from the ANR device's external environment reaching the user's ear canal at a resonant frequency corresponding to the resonant mode. In some implementations, the output audible sound generated by the acoustic transducer may be modified to smooth a transfer function representing the user's ear canal at a resonant frequency corresponding to the resonant mode. In some implementations, the output audible sound generated by the acoustic transducer may be 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. In some implementations, the output audible sound generated by the acoustic transducer may be further modified using broadband noise reduction at multiple frequencies below 2 kHz. In some implementations, the portion attributable to a resonant mode of the user's ear canal may be identified by considering the user's individualized ear canal response.In some implementations, one or more resonant frequencies corresponding to the resonant modes may be identified using a phase-locked loop and / or using a peak detection algorithm. In some implementations, one or more resonant frequencies corresponding to the resonant modes may be tracked in real time.

[0012] Another aspect features a method. The method includes capturing, at a first sensor of an active noise reduction (ANR) device, an audible sound originating from an environment external to the ANR device, generating an output audible sound at an acoustic transducer of the ANR device, and generating, at a second sensor of the ANR device, a signal indicative of (1) the audible sound originating from the environment external to the ANR device and (2) the output audible sound 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 audible sound generated by the acoustic transducer based on the identified portion of the signal generated by the second sensor.

[0013] Implementations may include 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 subportion attributable to a resonant mode of the user's ear canal from an audible sound originating from an environment external to the ANR device, deriving a second subportion attributable to a resonant mode of the user's ear canal from an output audible sound generated by the acoustic transducer, and combining the first subportion and the second subportion. In some implementations, modifying the output audible sound generated by the acoustic transducer may include modifying the output audible sound at a frequency between 3 kHz and 10 kHz, the frequency corresponding to the resonant mode of the user's ear canal. In some implementations, modifying the output audible sound generated by the acoustic transducer may include performing rate feedback on the portion of the signal generated by the second sensor attributable to the resonant mode. In some implementations, modifying the output audible sound generated by the acoustic transducer may include generating a signal indicative of the velocity of the resonant mode and summing the signal indicative of the velocity of the resonant mode with the output audible sound. In some implementations, generating a signal indicative of the velocity of the resonant mode may include multiplying the velocity of the resonant mode by a constant. In some implementations, generating a signal indicative of the velocity of the resonant mode may include filtering the portion of the signal generated by the second sensor. In some implementations, modifying the output audible sound generated by the acoustic transducer may include modifying the output audible sound at a resonant frequency corresponding to the resonant mode to attenuate audible sound from an environment external to the ANR device that reaches the user's ear canal. In some implementations, modifying the output audible sound at a resonant frequency corresponding to the resonant mode may include modifying the output audible sound to smooth a transfer function representing the user's ear canal.In some implementations, the method may further include identifying a second portion of the signal generated by the second sensor attributable to a second resonant mode of the user's ear canal and modifying the output audible sound 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 further include modifying the output audible sound generated by the acoustic transducer using broadband noise reduction at multiple frequencies below 2 kHz. In some implementations, identifying the portion of the signal generated by the second sensor attributable to a resonant mode of the user's ear canal may include considering the user's individualized ear canal response. In some implementations, identifying the portion of the signal generated by the second sensor attributable to a resonant mode of the user's ear canal of the ANR device may include identifying one or more resonant frequencies corresponding to the resonant modes using a phase-locked loop and / or a peak detection algorithm. In some implementations, identifying the portion of the signal generated by the second sensor attributable to a resonant mode of the user's ear canal of the ANR device may also include tracking the one or more resonant frequencies in real time.

[0014] Another aspect features one or more machine-readable storage devices having computer-readable instructions encoded thereon for causing one or more processing devices to perform operations, including capturing, at a first sensor of an active noise reduction (ANR) device, an audible sound originating from an environment external to the ANR device, generating an output audible sound at an acoustic transducer of the ANR device, and generating, at a second sensor of the ANR device, a signal indicative of (1) the audible sound originating from the environment external to the ANR device and (2) the output audible sound generated by the acoustic transducer. Each operation 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 audible sound generated by the acoustic transducer based on the identified portion of the signal generated by the second sensor.

[0015] Implementations may include 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 subportion attributable to a resonant mode of the user's ear canal from an audible sound originating from an environment external to the ANR device, deriving a second subportion attributable to a resonant mode of the user's ear canal from an output audible sound generated by the acoustic transducer, and combining the first subportion and the second subportion. In some implementations, modifying the output audible sound generated by the acoustic transducer may include modifying the output audible sound at a frequency between 3 kHz and 10 kHz, the frequency corresponding to the resonant mode of the user's ear canal. In some implementations, modifying the output audible sound generated by the acoustic transducer may include performing rate feedback on the portion of the signal generated by the second sensor attributable to the resonant mode. In some implementations, modifying the output audible sound generated by the acoustic transducer may include generating a signal indicative of the velocity of the resonant mode and summing the signal indicative of the velocity of the resonant mode with the output audible sound. In some implementations, generating a signal indicative of the velocity of the resonant mode may include multiplying the velocity of the resonant mode by a constant. In some implementations, generating a signal indicative of the velocity of the resonant mode may include filtering the portion of the signal generated by the second sensor. In some implementations, modifying the output audible sound generated by the acoustic transducer may include modifying the output audible sound at a resonant frequency corresponding to the resonant mode to attenuate audible sound from an environment external to the ANR device that reaches the user's ear canal. In some implementations, modifying the output audible sound at a resonant frequency corresponding to the resonant mode may include modifying the output audible sound to smooth a transfer function representing the user's ear canal.In some implementations, the operations may further include identifying a second portion of the signal generated by the second sensor attributable to a second resonant mode of the user's ear canal and modifying the output audible sound generated by the acoustic transducer based on the identified second portion of the signal generated by the second sensor. In some implementations, the operations may further include modifying the output audible sound generated by the acoustic transducer using broadband noise reduction at multiple frequencies below 2 kHz. In some implementations, identifying the portion of the signal generated by the second sensor attributable to a resonant mode of the user's ear canal may include considering the user's individualized ear canal response. In some implementations, identifying the portion of the signal generated by the second sensor attributable to a resonant mode of the user's ear canal of the ANR device may include identifying one or more resonant frequencies corresponding to the resonant modes using a phase-locked loop and / or a peak detection algorithm. In some implementations, identifying the portion of the signal generated by the second sensor attributable to a resonant mode of the user's ear canal of the ANR device may also include tracking the one or more resonant frequencies in real time.

[0016] Other features and advantages of the present description will become apparent from the following description and claims. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram showing an example of an in-ear active noise reduction headphone. [Figure 2] FIG. 1 is a block diagram of a first exemplary configuration of an acoustic device. [Figure 3] 3 is a graph of experimental data corresponding to an acoustic device having the exemplary configuration shown in FIG. 2. [Figure 4]FIG. 2 is a block diagram of a second exemplary configuration of an acoustic device. [Figure 5] 5 is a graph of experimental data corresponding to an acoustic device having the exemplary configuration shown in FIG. 4. [Figure 6] FIG. 10 is a block diagram of a third exemplary configuration of an acoustic device. [Figure 7] 7 is a graph of simulation data corresponding to an acoustic device having the exemplary configuration shown in FIG. 6. [Figure 8] FIG. 10 is a diagram of a Simulink® model representing a fourth exemplary configuration of an acoustic device. [Figure 9] 9 is a graph of experimental data corresponding to an acoustic device having the exemplary configuration shown in FIG. 8. [Figure 10] FIG. 10 is a diagram of a hardware implementation of a portion of an acoustic device according to a fifth exemplary configuration of the acoustic device. [Figure 11] 11 is a graph of experimental data corresponding to a hardware implementation of the exemplary configuration of the acoustic device shown in FIG. 10. [Figure 12] FIG. 10 is a block diagram of a sixth exemplary configuration of an acoustic device. [Figure 13] 1 is a graph illustrating modeling of multiple acoustic resonance modes in the acoustic response. [Figure 14] 1 is a flowchart of a process for actively attenuating audible sounds resulting from resonant modes in a user's ear canal. [Figure 15] FIG. 1 illustrates an example computing environment. DETAILED DESCRIPTION OF THE INVENTION

[0018] This document describes techniques that may 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 effects of ambient noise and sound. In some implementations, the active noise reduction device may include a feedforward microphone, a feedback microphone, an output transducer, and noise reduction circuitry coupled to the microphone and the output transducer to provide a noise countermeasure signal to the output transducer based on a signal detected at the microphone.

[0019] 1 , an acoustic implementation of in-ear active noise reduction headphones 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 acoustic transducer or driver or speaker), and noise reduction circuitry (not shown) coupled to both microphones 102, 104 and the output transducer 106 to provide a noise countermeasure signal to the output transducer 106 based on signals detected at both microphones 102, 104. An additional input to the circuitry (not shown in FIG. 1 ) provides an additional audio signal, such as music or a communication signal, for playback via the output transducer 106 independent of the noise reduction signal. More information regarding in-ear active noise reduction headphones 100 can be found, for example, in U.S. Pat. No. 9,082,388, which is incorporated herein by reference in its entirety.

[0020] In some implementations, the feedforward microphone 102 may be located on an outward-facing surface of the in-ear active noise reduction headphones 100 and may capture audible sounds from the environment external to the in-ear active noise reduction headphones 100. Thus, the feedforward microphone 102 may be referred to as an "external microphone."

[0021] In some implementations, the feedback microphone 104 may be positioned closer to the user's ear canal than the feedforward microphone 102. The feedback microphone 104 may be configured to capture audible sounds originating from the external environment as well as audible sounds output by the output transducer 106. In some cases, the feedback microphone 104 may be referred to as the "system microphone."

[0022] The noise reduction circuitry may include a configurable digital signal processor (DSP) that can implement various signaling topologies and filter configurations. Examples of such digital signal processors are described in U.S. Patent Nos. 8,073,150 and 8,073,151, which are incorporated by reference herein in their entireties.

[0023] The term headphones is used interchangeably with the term headset herein and includes various types of personal acoustic devices, such as in-ear, around-ear, over-ear, and open-ear headsets, earphones, and hearing aids. A headset or headphones can include an earbud or earcup for each ear. The earbuds or earcups may be physically tethered to each other, for example, by a cord, an overhead bridge or headband, or a rear-head retention structure. In some implementations, the earbuds or earcups of headphones may be connected to each other via a wireless link.

[0024] The active noise reduction headphones 100 offer a feature commonly referred to as "talk-through" or "monitor," in which the external microphone 102 is used to detect external sounds that the user wants to hear. In some implementations, the external microphone 102 may detect sounds in the voice band or some other frequency band of interest and allow signals in the corresponding frequency band to be sent through the active noise reduction headphones 100. In some other implementations, the active noise reduction headphones 100 allow multi-mode operation; in a "hear-through" mode, the active noise reduction function may be switched off or at least reduced over at least a range of frequencies, allowing a relatively broadband of ambient sounds to reach the user. In some implementations, the active noise reduction headphones 100 allow the user to control the amount of noise and ambient sounds that pass through the active noise reduction headphones 100.

[0025] In some implementations, an active noise reduction signal flow path is provided in parallel with a pass-through signal flow path, and the gain of the pass-through signal path is controllable by a user. This enables implementation of an active noise reduction device that can adjust the amount of ambient noise passing through (e.g., either in discrete steps or substantially continuously) based on user input without having to turn off or reduce the active noise reduction provided by the device. In some examples, this can improve the overall user experience, for example, by avoiding any audible artifacts associated with switching between active noise reduction and pass-through mode and / or by allowing the user to control the amount of ambient noise they want to hear. This can make the active noise reduction device easier to use in a variety of different applications and environments, particularly those in which a substantially continuous balance between active noise reduction and pass-through functionality is desirable.

[0026] Various signal flow topologies can be implemented in active noise reduction devices to enable functions such as audio equalization, feedback noise cancellation, and feedforward noise cancellation. Exemplary signal flow topologies are described in U.S. Patent No. 1,106,2687, which is incorporated herein by reference in its entirety. The techniques described herein can add these functions by enabling modal control of the audio response at one or more resonant frequencies between 3,000 Hz and 10,000 Hz.

[0027] FIG. 2 shows a block diagram of an exemplary configuration 200 of an acoustic device (e.g., ANR headphone 100) or a portion thereof. In configuration 200, a first audible sound signal 202 (signal “o”) is received by an external microphone (e.g., external microphone 102) and may include audible sound originating from the environment outside the acoustic device. For example, the audible sound may include noises from the environment or human voices that a user may not want to hear. Transfer function 206 (transfer function “Nso”) represents how audible sound 202 changes as it travels from the location of the external microphone to the device's system microphone (e.g., system microphone 104). Thus, signal 210 represents the altered audible sound originating from the external environment received at the system microphone.

[0028] In configuration 200, command signal 204 (signal "d") is input to a driver or speaker of the device (e.g., output transducer 106), driving the driver or speaker to generate a second audible sound signal. Transfer function 208 (transfer function "Gsd") represents how the audible sound output in accordance with command signal "d" 204 changes as it travels from the driver's location to the device's system microphone. Signal 212 therefore represents the changed output audible sound received at the system microphone.

[0029] In some implementations, the "Gsd" transfer function 208 can be affected by various characteristics, including driver design, microphone response, port design, ear canal shape, and fit quality. As a result, the "Gsd" transfer function 208 may vary between different devices, between different users, between different use cases by a single user, or even between different points in time during the same use case by a single user. Therefore, 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. Exemplary methods for measuring the "Gsd" transfer function 208 and its decomposed subcomponents (including variations thereon) are described in U.S. Pat. No. 1,093,7410, the entire contents of which are incorporated herein by reference.

[0030] From the measured “Gsd” transfer function 208 or from the time-domain audio signal, one or more resonant frequencies can be identified and / or tracked in time (e.g., in real time) using various techniques. For example, in some 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 implementations, tracking changes in resonant frequencies can include estimating a value representing the derivative of the acoustic response (e.g., with respect to frequency) at a particular suspected resonant frequency. For example, this can be done by measuring the frequency response at frequencies slightly below and slightly above the particular frequency. If the derivative is zero or substantially close to zero, the resonant frequency can be considered properly identified. However, if the derivative is substantially away from zero, the sign and magnitude of the derivative can be used to update the estimate of the suspected resonant frequency (e.g., according to a quadratic cost function). This process can be repeated until the resonant frequency is sufficiently identified. In some implementations, other peak identification algorithms may be implemented to identify and track resonant frequency peaks in the frequency domain. Once one or more resonant frequencies have been identified and / or tracked, active attenuation or cancellation of audible sounds at these resonant frequencies may be performed using techniques such as those described in further detail herein.

[0031] The system microphone captures an audible sound signal 216 (signal "s") that is a combination of signals 210 and 212. Thus, the captured audible sound signal "s" 216 may include audible sounds originating from the environment external to the acoustic device as well as audible sounds output by the driver of the acoustic device.

[0032] FIG. 3 shows graphs 300A-300D containing experimental data corresponding to an acoustic device having the configuration 200 shown in FIG. 2. Graph 300A plots audible response data corresponding to the "Nso" transfer function 206 and the "Gsd" transfer function 208. Trace 302 corresponds to the "Nso" transfer function, and trace 304 corresponds to the "Gsd" transfer function 208. Traces 302 and 304 all have peaks at frequencies between 4,000 Hz and 5,000 Hz (indicated by dotted line 306A). These peaks are caused by resonant behavior at these frequencies and correspond to resonant modes in the ear canal of a user of the acoustic device.

[0033] Graph 300B plots data representing the passive insertion gain (PIG) ​​of an acoustic device at various frequencies. Passive insertion gain is defined as the purely passive response of the ANR device when worn by a user, with lower values ​​being more desirable for noise reduction applications. In graph 300B, trace 308 represents PIG, which is also observed to peak at a resonant frequency (indicated by dotted line 306B in graph 300B). One important observation is that the resonant frequency 306B of a user's ear canal when an 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 mentioned, this shift in the resonant frequency of a user's ear canal when using an ANR device can 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.

[0034] In general, an audible sound signal may be cancelable at a location if the signal received at that location is coherent with an audible sound signal captured (e.g., by a microphone) at another location. Graphs 300C and 300D plot coherence data collected from experiments conducted to determine whether resonant responses can be canceled. In these experiments, in-ear ANR devices (similar to ANR device 100 shown in FIG. 1 ) were inserted into the ears of an artificial head, which included a microphone positioned within the ear canal (a “canal microphone”) to capture the audible sound signal “c.” While in practical applications, inserting a microphone into a user’s ear canal may be undesirable or impossible, in these experiments the canal microphone was placed inside the artificial head to determine what audible sounds might reach a real user’s ear canal.

[0035] Graph 300C shows the coherence limit (defined as 1 minus the coherence) between 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 canal microphone. Trace 312 shows the coherence between signal "o" 202 and signal "s" 216, while trace 314 shows the coherence between signal "o" 202 and signal "c." In both cases, higher coherence is indicated by a lower value of the coherence limit along the y-axis, which may be desirable for noise reduction applications. Traces 312, 314 all have a valley at the resonant frequency (indicated by dotted line 306C), suggesting that it is possible that at least a portion of these audible signals may be canceled.

[0036] Graph 300D shows the coherence limits of signal "c" captured by a 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 shows the coherence between the driver-related portion of signal "s" and signal "c." Meanwhile, trace 318 shows the coherence between the external noise-related portion of signal "s" and signal "c." Again, higher coherence is indicated by a lower value of the coherence limit along the y-axis, which may be desirable for noise reduction applications. Here, traces 316 and 318 also have a valley at the resonant frequency (indicated by dotted line 306D), suggesting that at least a portion of these audible signals may be canceled.

[0037] To cancel audible sounds resulting from resonant modes in the user's ear canal, the techniques described herein implement modal control. Conventional systems for active noise reduction often use broadband control, which measures frequency responses over a wide range of frequencies, rather than modal control. However, such measurements do not convey internal details about the underlying physical model, such as the ear canal having one or more resonant frequencies. In contrast, modal control can be implemented based on an underlying model of the plant's internal state (e.g., external noise and the output audible sound generated by an in-ear ANR device reaching the user's ear canal).

[0038] 4 shows a block diagram of an example configuration 400 of an acoustic device (or portion thereof) in which the Gsd transfer function 208 is decomposed into two parallel plant models 402, 404. Configuration 400 shares many similarities with configuration 200, and therefore, like elements are designated with like 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 plant 402 may be modeled using six biquad filters, and the Gsd1 plant 404 may be modeled using a single biquad filter. The Gsd6 plant 402 receives the audible signal corresponding to the command signal "d" 204 and outputs a wideband portion of the audible signal captured at the system microphone (signal "s6" 406). Meanwhile, the Gsd1 plant 404 receives the audible signal corresponding to the command signal "d" 204 and outputs a resonant mode portion (e.g., a portion of the audible sound due to a resonant mode) captured at the system microphone (signal "s1" 408). In some implementations, the combination of signal s1 408 and signal s6 406 may be substantially similar to signal 212 shown in FIG. 2. Signal 210, signal s6 406, and signal s1 408 may all be combined (e.g., summed) to calculate signal "s" 216. Compared to the configuration 200 shown in FIG. 2, the configuration 400 may have the advantage of isolating signal "s1" 408, which may allow for independent attenuation of the resonant mode (e.g., by operating independently on the resonant portion of the audible sound originating from the driver).

[0039] As mentioned above, in some implementations, the Gsd transfer function 208 may 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 may enable identification of one or more high-frequency resonant peaks corresponding to a particular individual's ear canal response, which may vary between users and / or between use cases of the ANR device (e.g., between a loose fit and a tight fit of the ANR device). Identifying individualized high-frequency resonant peaks in this manner may provide customized and individualized estimates of the Gsd1 plant 404 and the Gsd6 plant 402, which may advantageously result in more personalized noise reduction.

[0040] FIG. 5 shows graphs 500A and 500B containing experimental acoustic response data (plot points 502) corresponding to an acoustic device having the configuration 400 shown in FIG. 4. Graph 500A plots the magnitude of the acoustic response of the Gsd transfer function 208 at various frequencies, and graph 500B plots the phase of the acoustic response. Thus, trace 504 fitted to plot points 502 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) since it is a resonant-only response. Additionally, the estimated response of the Gsd1 filter 404 (resonant mode response) and the estimated response of the Gsd6 filter 402 (wideband response) sum to the overall response of the Gsd transfer function 208, as expected based on the configuration 400.

[0041] Referring now to FIG. 6, a block diagram of another exemplary configuration 600 of an acoustic device (or portion thereof) is shown. Configuration 600 shares many similarities with configuration 400, and therefore, like elements are designated with like reference numerals. However, in this configuration, the Nso transfer function 206 is also decomposed into two parallel plant models 602, 604. Similar to the Gsd transfer function, the Nso transfer function 206 is divided into a first filter 602 ("Nso6") corresponding to a wideband response and a second filter 604 ("Nso1") corresponding to a first modal response (resonant mode response). In some implementations, the Nso6 plant 602 may be modeled using six biquad filters, and the Nso1 plant 604 may be modeled using a single biquad filter. The Nso6 system 602 receives the signal "o" 202 and outputs the wideband portion of the signal "o" captured at the system microphone (signal 606). Meanwhile, the Nso1 plant 604 receives the signal "o" 202 and outputs the resonant mode portion (e.g., the portion of the audible sound due to the resonant mode) captured at the system microphone (signal 608). In some implementations, the combination of signal 608 and signal 606 can be substantially similar to signal 210 shown in FIGS. 2 and 4.

[0042] Another difference in configuration 600 compared to configuration 400 is that because both transfer functions 206, 208 are split into parallel plants, signal "s6" (audible sound due to wideband response) and signal "s1" (audible sound due to resonant response) may now include contributions from both the driver output (e.g., the audible sound output corresponding to driver command signal "d" 204) and the external noise (e.g., signal "o" 202). In configuration 600, signal "s6" 612 includes a combination (e.g., sum) of wideband signal 606 originating from the external environment and wideband signal 406 originating from the driver. Meanwhile, signal "s1" 610 includes a combination (e.g., sum) of resonant signal 608 originating from the external environment and resonant signal 408 originating from the driver. The combination (e.g., sum) of signal "s1" 610 and signal "s6" can result in the complete signal "s" 216 captured at the system microphone.

[0043] In configuration 600, isolating signal "s1" 610 (audible sound due to resonant response) may allow for independent damping of resonant modes. To this effect, if signal "s1" can be estimated, configuration 600 may include a damping feedback loop having a damping filter 614 acting on signal "s1" 610 to actively damp the audible sound due to the resonant mode. The damping loop may perform rate feedback on signal "s1" 610, effectively resisting the velocity of the resonant mode. For example, in some implementations, damping filter 614 may be a single biquad low-pass filter that multiplies the velocity of the resonant mode by a constant coefficient. The resulting signal may then be filtered by an external signal "d ext ” 616 to generate a driver command signal “d” 204, which is fed back to the driver to adjust the audible sound output of the driver.

[0044] 7 shows graphs 700A, 700B containing simulation data corresponding to an acoustic device having the configuration 600 shown in FIG. 6, demonstrating the potential improvement to ANR performance if the signal "s1" can be accurately estimated. Graph 700A plots the undamped response of the transfer function Nso (trace 702) as well as the modal damped response of the transfer function Nso (trace 704). Theoretically, the configuration 600 should produce a damped response of the transfer function Nso, which can be expressed as follows:

[0045]

number

[0046] Graph 700B plots the undamped response of transfer function Gsd (trace 706) as well as the modal damped response of transfer function Gsd (trace 708). In theory, configuration 600 should produce a damped response of transfer function Gsd, which can be expressed as follows:

[0047]

number

[0048] 8, there is shown a diagram of a Simulink® model representing another exemplary configuration of an acoustic device (or portion thereof) 800. Elements of configuration 800 that are similar to elements of previously described configurations (e.g., configurations 200, 400, 600) are indicated with similar reference numerals.

[0049] Similar to other configurations of an acoustic device, configuration 800 includes a plant 802 that receives as inputs signal "o" 202 and signal "d" 204. Plant 802 receives signals 202, 204 and simulates output signal "s" 216 that is captured at the system microphone of the acoustic device. In some implementations, plant 802 may correspond to configuration 200 shown in FIG. 2.

[0050] The output signal "s" 216 is provided to a state estimator 804 that receives a signal 812 representing the difference between the output signal "s" 216 and an 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 an amplifier 808 and delayed by a delay block 810.

[0051] The state estimator 804 further receives the signal "o" 202 and the signal "d" 204 as inputs and, based on the inputs (e.g., signals 202, 204, 812), estimates the resonant response signal (signal "s1" 610) and its modal velocity 814. Similar to the configuration 600, in the configuration 800, the modal velocity 814 can be fed through a damping loop and the resulting signal can be used to generate the command signal "d" 204 (e.g., signal "d" 610). ext 8, the damping group may include a damping filter 816 (e.g., a biquad filter), a delay block 818, and an amplifier 820. In some implementations, the resonance response signal (signal "s1" 610) may be fed directly to the damping loop (e.g., instead of the modal velocity 814), and the damping filter 816 of the damping loop may be configured to take the derivative of signal "s1" 610 to obtain the modal velocity.

[0052] 9 shows graphs 900A and 900B containing experimental response data corresponding to an acoustic device having the configuration 800 shown in FIG. 8. Graph 900A plots the magnitude of various acoustic responses at different frequencies, and graph 900B plots the phase of the same acoustic responses. Trace 902 corresponds to the response of a complete, undamped Gsd transfer function (e.g., Gsd transfer function 208 included in plant 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.

[0053] Trace 902, corresponding to the undamped Gsd transfer function, exhibits a substantial peak at frequencies between 5,000 Hz and 6,000 Hz due to a resonant mode in the user's ear canal. However, as shown by traces 904 and 906 (which are very similar to each other), after using mode control to perform active damping on the resonant mode, both the simulated damped response and the laboratory-measured response exhibit a substantial reduction in this peak, effectively smoothing the response at the resonant frequency.

[0054] 10, there is shown a diagram of a hardware implementation of a portion of an acoustic device (e.g., a processor of the acoustic device executing software to implement an estimator and a damping controller). The hardware implementation is shown having a configuration 1000. Elements of configuration 1000 that are similar to elements of previous configurations of the acoustic device (e.g., configurations 200, 400, 600, 800) are indicated with similar reference numbers.

[0055] In configuration 1000, signal "o" 202 (captured by the acoustic device's external microphone) is fed through Nso1 filter 604 to produce signal 608 (representing the portion of the external noise captured at the system microphone that is attributable to resonant modes). Meanwhile, signal "s" 216 captured at the system microphone is delayed and combined in subtractor 1002 with an estimate of signal "s1" 610 (representing the portion of the total audible sound captured at the system microphone that is attributable to resonant modes). The output of subtractor 1002 is difference signal "s-s1" 806, which is amplified by amplifier 808 and combined with driver command signal "d" 204 in summer 1004 and fed through Gsd1 filter 404 to produce signal 408. As previously explained, signal 408 represents the portion of the driver output audible sound captured at the system microphone that is attributable to resonant modes. In summer 1006, signals 408 and 608 are combined to calculate an updated estimate of signal “s1” 610. In addition to being fed back to summer 1002, signal “s1” 610 is input to attenuation filter 816 (which may be configured to obtain the modal velocity of signal “s1” 610) and scaled by amplifier 820. The resulting signal is combined with external signal “d_ext” 616 in mixer 1008, and the combined signal is clipped in clipping module 1010. The resulting signal is the updated driver command signal “d” 204 ​​and is fed back to summer 1004.

[0056] FIG. 11 is a graph 1100 containing experimental acoustic response data corresponding to a hardware implementation of an acoustic device including components corresponding to configuration 1000. Trace 1102 corresponds to the PIG of the acoustic device, exhibiting a peak between 3,000 Hz and 4,000 Hz, corresponding to a resonant mode of a user's ear canal. Trace 1104 corresponds to the acoustic response of the same device after implementing active damping of the resonant mode in accordance with configuration 1000. As shown in graph 1100, trace 1004 substantially reduces the acoustic response at the resonant frequency. Furthermore, the level of reduction is adjustable 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 doubling the damping loop gain compared to the value that produced trace 1004; as expected, trace 1106 exhibits an even greater reduction in the acoustic response at the resonant frequency.

[0057] 12, a block diagram of another exemplary configuration 1200 of an acoustic device (or portion thereof) is shown. Configuration 1200 is nearly identical to configuration 600, and therefore, like elements are designated with like reference numerals. However, configuration 1200 differs from configuration 600 because it includes an additional feedback loop in which signal “s” 216 captured at the system microphone is fed through a feedback filter 1202 and the resulting signal is summed with driver signal “d” 204. While some of the configurations previously described in this document (e.g., configurations 600, 800, 1000) included 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., wideband control based on feedback and feedforward signals) in a single acoustic device.

[0058] In some implementations, the techniques described herein can be further extended to include modal control of multiple resonant modes simultaneously (e.g., using damping feedback loops). FIG. 13 shows graph 1300 demonstrating that a model fitting approach can successfully decompose a complete, undamped transfer function Gsd (e.g., Gsd transfer function 208) into a broadband response 1302 and three distinct resonant responses 1304A-1304C. This can be understood as an extension of the single resonant mode modeling approach demonstrated in graph 500A of FIG. 5. Accordingly, 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.

[0059] Although the damping loops described above are described as feedback loops, in some implementations, the feedback damping loops described herein may be equivalently implemented as a combination of a feedback filter and a feedforward filter. For example, referring again to FIG. 10, the equivalent feedback and feedforward filters may have the following transfer functions, respectively:

[0060]

number

[0061]

number

[0062] 14 shows an example process 1400 for actively attenuating audible sounds resulting from resonant modes in a user's ear canal. In some implementations, the operations of process 1400 may be performed by an acoustic device such as the in-ear ANR device 100 shown in FIG.

[0063] The operations of process 1400 include capturing, at a first sensor of an active noise reduction (ANR) device, an audible sound originating from an environment external to the ANR device. In some implementations, the first sensor may correspond to an external microphone of the ANR device (e.g., external microphone 102). The audible sound originating from the environment external to the ANR device may correspond to signal "o" 202.

[0064] The operations of process 1400 also include generating an output audible sound at an acoustic transducer of the ANR device. The acoustic transducer may correspond to output transducer 106 shown in FIG. 1 or may be another speaker or driver of an acoustic device as described throughout this disclosure. The generated output audible sound may correspond to signal “d” 204.

[0065] The operations of process 1400 also include generating, at a second sensor of the ANR device, a signal indicative of (1) an audible sound originating from an environment external to the ANR device and (2) an output audible sound generated by the acoustic transducer. In some implementations, the second sensor can correspond to a system microphone of the acoustic device (e.g., system microphone 104), and the generated signal can correspond to the audible sound captured by the system microphone (e.g., signal “s” 216).

[0066] The operations of process 1400 also include identifying a portion of the signal generated by the second sensor attributable to a resonant mode of the user's ear canal of the ANR device. For example, the portion of the signal generated by the second sensor attributable to a resonant mode may correspond to signal "s1" 610 described above. Identifying the portion of the signal generated by the second sensor may include deriving a first subportion (e.g., signal 608) attributable to a resonant mode of the user's ear canal from an audible sound originating in an environment external to the ANR device. Identifying the portion of the signal generated by the second sensor may further include deriving a second subportion (e.g., signal 408) attributable to a resonant mode of the user's ear canal from an output audible sound generated by the acoustic transducer. Identifying the portion of the signal generated by the second sensor may further include combining the first subportion and the second subportion (e.g., by summing them).

[0067] The operations of process 1400 also include modifying the output audible sound generated by the acoustic transducer based on the identified portion of the signal generated by the second sensor. Modifying the output audible sound may include modifying the output audible sound at a frequency between 3 kHz and 10 kHz. For example, the frequency may correspond to a resonant mode of the user's ear canal. Modifying the output audible sound may also include generating a signal indicative of the velocity of the resonant mode and summing the signal with the output audible sound. Generating the signal indicative of the velocity of the resonant mode may include multiplying the velocity of the resonant mode by a constant. Generating the signal indicative of the velocity of the resonant mode may also include filtering (e.g., using filter 816) the portion of the signal generated by the second sensor (e.g., signal "s1" 610). In some implementations, modifying the output audible sound may include modifying the output audible sound to smooth a transfer function representing the user's ear canal at a resonant frequency corresponding to the resonant mode.

[0068] Additional operations of process 1400 may include the following. In some implementations, process 1400 may include identifying a second portion of the signal generated by the second sensor that is attributable to a second resonant mode of the user's ear canal. In such implementations, process 1400 may further include modifying the output audible sound generated by the acoustic transducer based on the identified second portion. In some implementations, process 1400 may include modifying the output audible sound generated by the acoustic transducer using broadband noise reduction at multiple frequencies below 2 kHz.

[0069] 15 illustrates an example of a computing device 1500 and a mobile computing device 1550 employed to perform implementations of the present disclosure. Computing device 1500 is intended to represent various forms of digital computers, such as laptops, desktops, workstations, personal digital assistants, servers, blade servers, mainframes, and other suitable computers. Mobile computing device 1550 is intended to represent various forms of mobile devices, such as personal digital assistants, cellular phones, smartphones, AR devices, and other similar computing devices. The components, their connections and relationships, and their functions shown here are intended to be exemplary only and not limiting. Computing device 1500 and / or mobile computing device 1550 can form at least a portion of an acoustic device, such as the in-ear ANR device 100 described above.

[0070] 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 connects to the memory 1504 and a plurality of high-speed expansion ports 1510. In some implementations, the low-speed interface 1512 connects to a 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 are interconnected using various buses and may be implemented on a common motherboard or in any other suitable manner. The processor 1502 can process instructions for execution within the computing device 1500, such as instructions stored in the memory 1504 and / or the storage device 1506, to display graphical information for 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 implementations, multiple processors and / or multiple buses may be used, along with multiple memories and multiple types of memory, as needed. Furthermore, multiple computing devices may be connected, each providing a portion of the required operations (e.g., as a bank of servers, a group of blade servers, or a multiprocessor system).

[0071] The memory 1504 stores information within the computing device 1500. In some implementations, the memory 1504 is a volatile memory unit. 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.

[0072] The storage device 1506 can provide mass storage for the computing device 1500. In some implementations, the storage device 1506 can be or include a computer-readable medium, such as a floppy disk device, a hard disk device, an optical disk device, a tape device, a flash memory, or other similar solid-state memory device, or an array of devices, including devices in a storage area network or other configuration. The instructions can be stored on an information carrier. When executed by one or more processing devices, such as the processor 1502, the instructions perform one or more methods, such as those described herein. The instructions can also be stored by one or more storage devices, such as a computer-readable or machine-readable medium, such as the memory 1504, the storage device 1506, or a memory on the processor 1502.

[0073] The high-speed interface 1508 manages bandwidth-intensive operations for the computing device 1500, and the low-speed interface 1512 manages less bandwidth-intensive operations. This allocation of functionality is merely an example. In some implementations, the high-speed interface 1508 is coupled to the memory 1504, the display 1516 (e.g., via a graphics processor or accelerator), and to a high-speed expansion port 1510 that may accept various expansion cards. In this 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 may include various communication ports (e.g., Universal Serial Bus (USB), Bluetooth, Ethernet, wireless Ethernet) and may be coupled to one or more input / output devices. Such input / output devices may include a scanner, a printing device, or a keyboard or mouse. Input / output devices may also be coupled to the low-speed expansion port 1514 via a network adapter. Such network input / output devices may include, for example, a switch or a router.

[0074] Computing device 1500 may be implemented in many different forms, as shown in Figure 15. For example, it may be implemented as a standard server 1520, or multiple times in a group of such servers. It may also be implemented in a personal computer, such as a laptop computer 1522. It may also be implemented as part of a rack server system 1524. Alternatively, components from computing device 1500 may be combined with other components in a mobile device, such as mobile computing device 1550. Each such device may include one or more of computing device 1500 and mobile computing device 1550, and the entire system may be composed of multiple computing devices communicating with each other.

[0075] The mobile computing device 1550 includes, among other components, a processor 1552, a memory 1564, an input / output device such as a display 1554, a communication interface 1566, and a transceiver 1568. The mobile computing device 1550 may also be provided with a storage device such as a microdrive or other device to provide additional storage. Each of the processor 1552, memory 1564, display 1554, communication interface 1566, and transceiver 1568 are interconnected using various buses, and some of the components may be mounted on a common motherboard or otherwise mounted as needed. In some implementations, the mobile computing device 1550 may include a camera device.

[0076] The processor 1552 can execute instructions within the mobile computing device 1550, including instructions stored in the memory 1564. The processor 1552 may be implemented as a chipset of chips including separate analog and digital processors. For example, the processor 1552 may be a Complex Instruction Set Computer (CISC) processor, a Reduced Instruction Set Computer (RISC) processor, or a Minimal Instruction Set Computer (MISC) processor. The processor 1552 may provide coordination of other components of the mobile computing device 1550, such as, for example, control of a user interface (UI), control of applications executed by the mobile computing device 1550, and / or control of wireless communications by the mobile computing device 1550.

[0077] The processor 1552 can communicate with a user via a control interface 1558 and a display interface 1556 coupled to a display 1554. The display 1554 may be, for example, a thin film transistor liquid crystal display (TFT) display, an organic light emitting diode (OLED) display, or other suitable display technology. The display interface 1556 may include appropriate circuitry for driving the display 1554 to present graphical and other information to the user. The control interface 1558 may receive commands from the user and translate them for provision to the processor 1552. Additionally, an external interface 1562 may provide communication with the processor 1552 to enable short-range communication between the mobile computing device 1550 and other devices. The external interface 1562 may provide, for example, wired communication in some implementations or wireless communication in other implementations, and multiple interfaces may be used.

[0078] Memory 1564 stores information within mobile computing device 1550. Memory 1564 may be implemented as one or more computer-readable media, one or more volatile memory units, or one or more nonvolatile memory units. Expansion memory 1574 may also be provided and connected to mobile computing device 1550 via expansion interface 1572, which may include, for example, a Single In-Line Memory Module (SIMM) card interface. Expansion memory 1574 may provide additional storage space for mobile computing device 1550 or may store applications or other information for mobile computing device 1550. Specifically, expansion memory 1574 may include instructions for performing or supplementing the processes described above and may also include secure information. Thus, for example, expansion memory 1574 may be provided as a security module for mobile computing device 1550 and may be programmed with instructions that enable secure use of mobile computing device 1550. Additionally, secure applications can be provided via SIMM cards along with additional information, such as placing identifying information on the SIMM card in a non-hackable manner.

[0079] The memory may include, for example, flash memory and / or non-volatile random access memory (NVRAM), as described below. In some implementations, the instructions are stored on an information carrier. When executed by one or more processing devices, such as processor 1552, the instructions 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, for example, via transceiver 1568 or external interface 1562.

[0080] The mobile computing device 1550 may communicate wirelessly via a communication interface 1566, which may include digital signal processing circuitry if necessary. The communication interface 1566 may provide communications under various modes or protocols, such as Global System for Mobile communications (GSM) voice calls, Short Message Service (SMS), Enhanced Messaging Service (EMS), Multimedia Messaging Service (MMS) messaging, 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), etc. Such communications may occur via a transceiver 1568 using, for example, radio frequencies. Further, short-range communication may occur using, for example, Bluetooth or Wi-Fi. Additionally, a Global Positioning System (GPS) receiver module 1570 may provide additional navigation-related and location-related wireless data to the mobile computing device 1550, which may be used as appropriate by applications running on the mobile computing device 1550.

[0081] The mobile computing device 1550 may also communicate audibly using an audio codec 1560, which may receive voice information from a user and convert it into usable digital information. The audio codec 1560 may also generate audible sounds for the user, such as through a speaker in the handset of the mobile computing device 1550. Such sounds may include sounds from a voice call, recorded sounds (e.g., voice messages, music files, etc.), and sounds generated by applications running on the mobile computing device 1550.

[0082] The mobile computing device 1550 may be implemented in many different forms, as shown in Figure 15. For example, it may be implemented in a telephone device 1580, a personal digital assistant 1582, and a tablet device (not shown). The mobile computing device 1550 may also be implemented as a component of a smartphone, an AR device, or other similar mobile device.

[0083] The computing device 1500 may be implemented as part of an acoustic device, such as the in-ear ANR device described above with respect to FIG.

[0084] Computing device 1500 and / or 1550 may also include a USB flash drive, which 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.

[0085] Other embodiments and applications not specifically described herein are also within the scope of the following claims. Elements of different implementations described herein may be combined to form other embodiments. [Explanation of symbols]

[0086] 100 In-ear ANR devices 102 Feedforward Microphone 104 Feedback Microphone 106 Output Transducer 200 configurations 202, 204 signal 206 Nso transfer function 208 Gsd transfer function 210, 212 signal 216 Audible signal 300A~300D graph 302 Trace 304 Trace 306A dotted line 306B dotted line 306C dotted line 306D dotted line 308 Trace 310 resonant frequency 312 Trace 314 Trace 316 Trace 318 Trace 400 configurations 402 First Filter 404 Second Filter 406 Wideband Signal 408 signal 500A graph 500B graph 502 points 502 plot points 504 Trace 506 Trace 508 Trace 600 configurations 602 First Filter 604 Second Filter 606 signal 608 signal 614 Attenuation Filter 700A graph 700B graph 702 Unattenuated Trace 702 Trace 704 Decay Trace 706 Unattenuated Trace 708 Decay Trace 800 configuration 802 Plant 804 State Estimator 806 difference 808 Amplifier 810 Delay Block 812 signal 814 mode speed 816 Attenuation Filter 818 Delay Block 820 Amplifier 900A graph 900B graph 902 Trace 904 Trace 906 Trace 1000 configurations 1002 Subtractor 1004 Adder 1006 Adder 1008 Mixer 1010 Clipping Module 1100 graphs 1102 Trace 1104 Trace 1106 Trace 1200 configuration 1202 Feedback Filter 1300 graphs 1302 wideband response 1304A~1304C Resonance Response 1400 processes 1500 computing devices 1502 processor 1504 memory 1506 Storage Devices 1508 high speed interface 1510 High-Speed ​​Expansion Port 1512 low speed interface 1514 Low-Speed ​​Expansion Port 1516 Display 1520 Standard Server 1522 laptop computer 1524 Rack Server System 1550 Mobile Computing Devices 1552 processor 1554 Display 1556 Display Interface 1558 Control Interface 1560 Audio Codec 1562 External Interface 1564 memory 1566 communication interface 1568 transceiver 1572 Expansion Interface 1574 extended memory 1580 Phone Device 1582 Mobile Information Terminal

Claims

1. 1. An active noise reduction (ANR) device comprising: an acoustic transducer configured to generate an output sound; a first sensor configured to capture audible sounds originating from an environment external to the ANR device; a second sensor, (1) the audible sound originating from the external environment; and (2) a second sensor configured to generate a signal indicative of the output audible sound generated by the acoustic transducer; An ANR device, wherein the output audible sound 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.

2. the portion of the signal generated by the second sensor attributable to the resonant mode; a first subportion derived from the audible sound originating from the external environment of the ANR device; a second subportion derived from the output audible sound produced by the acoustic transducer.

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

4. 10. The ANR device of claim 1, wherein the output audible sound is modified by rate feedback on the portion of the signal produced by the second sensor that is attributable to the resonant mode.

5. 10. The ANR device of claim 1, wherein the output audible sound is modified by summing with the output audible sound a signal indicative of the velocity of the resonant mode.

6. The ANR device of claim 5 , wherein the signal indicative of the velocity of the resonant mode represents a multiple of the velocity of the resonant mode.

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

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

9. 2. The ANR device of claim 1, wherein the output audible sound generated by the acoustic transducer is modified to attenuate the audible sound originating from the environment external to the ANR device reaching the user's ear canal at a resonant frequency corresponding to the resonant mode.

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

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

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

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

14. The ANR device of claim 1 , wherein one or more resonant frequencies corresponding to the resonant modes have been 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 modes are tracked in real time.

16. 1. A method comprising: capturing, at a first sensor of an active noise reduction (ANR) device, an audible sound originating from an environment external to the ANR device; generating an output audible sound at an acoustic transducer of the ANR device; In the second sensor of the ANR device, (1) the audible sound originating from the environment external to the ANR device; and (2) generating a signal indicative of the output audible sound produced by the acoustic transducer; 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 audible sound produced by the acoustic transducer based on the identified portion of the signal produced by the second sensor.

17. identifying the portion of the signal produced by the second sensor; deriving a first subportion attributable to the resonant mode of the ear canal of the user from the audible sound originating from the environment external to the ANR device; deriving a second subportion from the output audible sound generated by the acoustic transducer that is attributable to the resonant mode of the ear canal of the user; combining the first sub-portion and the second sub-portion.

18. 17. The method of claim 16, wherein modifying the output audible sound produced by the acoustic transducer comprises modifying the output audible sound at frequencies between 3 kHz and 10 kHz, the frequencies corresponding to the resonant modes of the ear canal of the user.

19. 17. The method of claim 16, wherein modifying the output audible sound produced by the acoustic transducer comprises performing rate feedback on the portion of the signal produced by the second sensor that is attributable to the resonant mode.

20. Modifying the output audible sound produced by the acoustic transducer comprises: generating a signal indicative of the velocity of the resonant mode; and summing the signal indicative of the velocity of the resonant mode with the output audible sound.

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

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

23. 17. The method of claim 16, wherein modifying the output audible sound generated by the acoustic transducer comprises modifying the output audible sound to attenuate the audible sound originating from the environment external to the ANR device reaching the user's ear canal at a resonant frequency corresponding to the resonant mode.

24. 17. The method of claim 16, wherein modifying the output audible sound produced by the acoustic transducer comprises modifying the output audible sound to smooth a transfer function representing the user's ear canal at a resonant frequency corresponding to the resonant mode.

25. identifying a second portion of the signal generated by the second sensor that is attributable to a second resonant mode of the ear canal of the user; modifying the output audible sound produced by the acoustic transducer based on the identified second portion of the signal produced by the second sensor; 17. The method of claim 16, further comprising:

26. 17. The method of claim 16, further comprising modifying the output audible sound produced by the acoustic transducer using broadband noise reduction at multiple frequencies below 2 kHz.

27. identifying the portion of the signal generated by the second sensor that is attributable to the resonant modes of the ear canal of the user; 17. The method of claim 16, comprising taking into account the user's individualized ear canal response.

28. identifying the portion of the signal generated by the second sensor that is attributable to the resonant modes of the ear canal of the user of the ANR device; 17. The method of claim 16, comprising identifying one or more resonant frequencies corresponding to the resonant modes using a phase-locked loop and / or using a peak detection algorithm.

29. identifying the portion of the signal generated by the second sensor that is attributable to the resonant modes of the ear canal of the user of the ANR device; 30. The method of claim 28, further comprising tracking the one or more resonant frequencies in real time.

30. one or more machine-readable storage devices having computer-readable instructions encoded thereon, the computer-readable instructions configured to cause one or more processing devices to: capturing, at a first sensor of an active noise reduction (ANR) device, an audible sound originating from an environment external to the ANR device; generating an output audible sound at an acoustic transducer of the ANR device; In the second sensor of the ANR device, (1) the audible sound originating from the environment external to the ANR device; and (2) generating a signal indicative of the output audible sound produced by the acoustic transducer; 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 audible sound produced by the acoustic transducer based on the identified portion of the signal produced by the second sensor.

Images