Wearable device and signal processing method

Abstract

To provide a wearable device and a signal processing method that can establish SPD (sound generating driver / device for true wireless stereo earphones)-ASM (ambient sensing microphone) separation.SOLUTION: A wearable device 10 includes a sound generating device 102 and a sound sensing device 107. During sound generation, the sound generating device generates a forward radiating wave through a front channel 109 via a front port 103 and a rear radiating wave through a rear channel 108 via a rear port 106. The sound sensing device is positioned at a nodal position where the forward radiating wave and the rear radiating wave cancel each other out at the nodal position.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a wearable device and a signal processing method, and more particularly to a wearable device and a signal processing method capable of establishing SPD-ASM separation. [Background technology]

[0002] In recent years, a new style of true wireless earphones has emerged.

[0003] In conventional true wireless earphones (referred to herein as TWS (known as true wireless stereo) for brevity), it is common practice to insert the tip of a silicone / foam covered acoustic tube into the listener's ear canal to create a semi / fully closed space between the sound generating driver / device (SPD) of the TWS earphone and the listener's eardrum.

[0004] Such an implementation achieves two effects: 1) improved bass performance, and 2) ambient / ear canal isolation.

[0005] In contrast to TWS practices, new "open-wear style" true wireless earphones (referred to herein for brevity as OWS (also known as Open Wearable Stereo)) are characterized by leaving the ear canal opening unblocked, allowing air to move freely in and out of the ear canal. Such OWS earphones are typically praised for being more comfortable, producing a more natural sound, and allowing users to be more aware of their surroundings. Because air can flow naturally in and out of the ear, they cause much less fatigue than previous-generation TWS earphones and can therefore be worn for extended periods of time without the user experiencing physical discomfort or subliminal / mental imbalances induced by acoustic isolation.

[0006] One of the major technological advancements in non-open / closed TWS earphones is the concept of Active Noise Cancellation (ANC) and Intelligent Ambient Pass-Through, or commonly known as Ambient Control (AC).

[0007] In closed-type TWS earphones, the earphone housing and (foam or silicone covered) tip divide the space around the listener's ear into three compartments: 1) the listener's ear canal in addition to the front chamber of the sound generating driver / device (SPD); 2) the back chamber of the SPD, which contains subcomponents such as the SPD, electronics, battery, etc. inside the earphone housing; and 3) the perimeter outside the earphone housing.

[0008] In these closed-type TWS earphones, ANC is typically controlled according to two types of microphones (sound sensing devices, SSDs): 1) a feedforward microphone (FFM) for sensing sound outside the earphone and providing a signal related to the ambient sound in the feedforward signal path, and 2) a feedback microphone (FBM) for sensing sound within the spatial volume of the front chamber + ear canal and providing a signal related to the result of ANC (i.e., residual ambient noise in the front chamber + ear canal) in the feedback signal path.

[0009] In the above configuration, the three-compartment virtualization allows the closed TWS earphone housing to isolate FFM from the sound generated by the earphone's own SPD, as well as isolate FBM from ambient sounds.

[0010] In other words, in occluded TWS earphones, by creating three compartments using the earphone housing, the FFM is largely isolated from (or unaware of) the sound generated by the earphone, while the FBM is largely isolated from (or unaware of) the ambient sound outside the earphone. These two "isolation" or "oblivions" are the key foundation that enables the powerful ANC features in occluded TWS earphones.

[0011] However, in OWS, the space is no longer subdivided to provide the separation described above (as in TWS), and sound from the SPD of the OWS earphones will be detected by any microphone. As a result, the FBM can no longer distinguish between ambient sound and sound generated by the OWS's own SPD, and the FBM can no longer monitor the ANC / AC results without the interference of ambient sound. This means that the infrastructure to support ANC / AC functionality in occluded TWS earphones no longer exists in new-style OWS earphones.

[0012] Therefore, how to provide isolation between the SPD and the ambient sensing microphone for ANC or AC under OWS scenarios is an important objective in the art. Summary of the Invention [Problem to be solved by the invention]

[0013] Therefore, the main objective of this application is to provide isolation between the SPD and the ambient sensing microphone to remedy the shortcomings of the prior art. [Means for solving the problem]

[0014] An embodiment of the present invention provides a wearable device, comprising a sound generating device and a sound sensing device, the sound generating device generating a sound and generating a forward radiation wave and a backward radiation wave, and the sound sensing device being disposed at a nodal position where the forward radiation wave and the backward radiation wave cancel each other out at the nodal position. [Effects of the Invention]

[0015] An embodiment of the present invention provides a wearable device comprising a sound generating device, a sound sensing device, and a signal processing circuit, the signal processing circuit receiving a sensed signal generated by the sound sensing device, the signal processing circuit performing an operation on the sensed signal to generate a clean ambient signal, the operation configured to reduce a sound signal component corresponding to the sound generated by the sound generating device.

[0016] An embodiment of the present invention provides a signal processing method applied to a signal processing circuit located in a wearable device, the signal processing method including receiving a sensed signal from a sound sensing device located in the wearable device, and performing an operation on the sensed signal to reduce a sound signal component corresponding to a sound generated by a sound generating device located in the wearable device and generate a clean ambient signal, the wearable device generating sound into an open field when the wearable device is worn by a user.

[0017] These and other objects of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic diagram of a wearable device according to an embodiment of the present invention. [Figure 2] 1 is a schematic diagram of a wearable device according to an embodiment of the present application; [Figure 3] 3 shows the distribution of acoustic energy in forward and rearward radiating waves over the space surrounding the wearable device shown in FIG. 2. [Figure 4] 1 is a schematic diagram of a wearable device according to an embodiment of the present invention. [Figure 5] 1 is a schematic diagram of a wearable device according to an embodiment of the present application; [Figure 6]1 shows the amplitude response curves corresponding to the forward and backward radiating waves and the discrepancy between the forward and backward radiating waves in terms of SPL versus frequency. [Figure 7] 1 shows a schematic diagram of a signal processing circuit according to an embodiment of the present invention; [Figure 8] 1 shows a schematic diagram of a signal processing chain according to one embodiment of the present invention; [Figure 9] 1 shows a schematic diagram of a signal processing circuit according to an embodiment of the present invention; [Figure 10] 1 is a schematic diagram of a wearable device according to an embodiment of the present invention. [Figure 11] 1 shows a schematic diagram of a system according to one embodiment of the present invention; [Figure 12] 1 shows a schematic diagram of a system according to one embodiment of the present invention; [Figure 13] 1 is a schematic diagram of a wearable device including a signal processing circuit according to an embodiment of the present invention. [Figure 14] 1 is a schematic diagram of a wearable device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] To provide ANC (Active Noise Cancellation) or AC (Ambient Control), an ASM (Ambient Sensing Microphone) is required to capture ambient sounds. In this application, AC generally refers to a technology that controls / manages the ambient sounds perceived by a listener / user.

[0020] The objective of this application is to establish separation between the SPD (sound generating device) and the ASM (ambient sensing microphone, which is a type of sound sensing device) so that the ANC / AC module can obtain clean ambient sound that does not contain sound / signal components corresponding to the sound generated by the SPD, or so that the sound / signal components corresponding to the sound generated by the SPD in the clean ambient sound are reduced or minimized as much as possible.

[0021] In this application, the isolation between the SPD and the ASM can be established via acoustic and / or electrical means. For the acoustic means, it is proposed to place the ASM at a nodal position where the forward and backward radiation waves of the SPD cancel each other. For the electrical means, a signal processing operation is performed on the sensed sound / signal from the ASM, so that the sound / signal component corresponding to the sound generated by the SPD is reduced / minimized, resulting in a clean ambient sound / signal. Preferably, both acoustic and electrical means can be applied, but are not limited thereto.

[0022] FIG. 1 is a schematic diagram of a wearable device 10 according to one embodiment of the present invention. The wearable device 10 includes a housing 105, a sound generating device (SPD) 102, and a sound sensing device (SSD) 107, which functions as an ASM for capturing ambient sound. The SPD 102 can divide the space within the wearable device 10 into a front chamber 101 and a rear chamber 104. The housing 105 defines a front port 103 and a rear port 106. The rear chamber 104 can house the device's electronics, battery, and wiring. The wearable device 10 can be an open-wear style or open-wear stereo (OWS) earphone. This means that the wearable device 10 is designed so that, when worn by a user, the wearable device 10 generates sound toward a slightly open or open area rather than toward a closed ear canal. During sound generation, the SPD 102 generates a forward radiating wave through the front channel 109 via the front port 103 and a rear radiating wave through the rear channel 108 via the rear port 106. Note that the front and rear radiating waves typically have similar or identical amplitudes but opposite polarities.

[0023] In this application, a wearable device generating sound toward an open field can generally be interpreted as a sound propagation path in which the sound outlet (e.g., port 103 / 106 shown in FIG. 1 ) is a certain distance (e.g., D103 / D106) away from the ear canal 110 of the ear canal when the wearable device is worn by a user. This means that sound radiates from the sound outlet, propagates through an open or somewhat open space, and then reaches the ear canal (e.g., 110). In this specification, "slightly open" refers to "not obstructed." In other words, a wearable device generating sound toward an open field can also generally be interpreted as a wearable device in which the acoustic radiation path / channel between the sound outlet and the ear canal 110 is not obstructed / closed. In this case, the forward / backward radiation waves generated by the SPD are (significantly) captured by the SSD / ASM of the wearable device.

[0024] To mitigate / avoid the problem of ambient sound captured by the ASM being contaminated by sound generated by the SPD, the SSD 107 (which functions as an ASM) may be placed at a nodal plane or nodal position, where the forward and backward radiating waves can cancel each other or destructively interfere with each other.

[0025] Illustratively, Figure 2 shows a diagram of a commercially available OWS wearable device 20 worn on the ear with front port 203 and rear port 206, where 210 indicates the ear canal. Using a simulation tool such as COMSOL, Figure 3 shows the distribution of acoustic energy in forward and rearward radiating waves (1.5 KHz as an example) across the space around the wearable device 20 based on specific front / rear port locations.

[0026] The shading in Figure 3 indicates the strength of acoustic energy. The darker the area, the stronger the acoustic energy above it, regardless of its polarity. The right half of Figure 3 is dominated by forward radiating waves, while the left half of Figure 3 is dominated by backward radiating waves. As can be seen in Figure 3, the light band between the right and left parts of Figure 3 indicates the nodal plane, where no / little acoustic energy remains. This is because the forward radiating waves and backward radiating waves cancel each other out at the nodal plane, which is a collection of nodal positions.

[0027] From the above illustration, it can be inferred that if the nodal plane is ideally formed (which means it does not move with frequency) and the ASM / SSD is located exactly on this plane, the sound waves from the SPD will produce zero (none) or nearly zero (slightly) output on the ASM / SSD, i.e., the sound from the SPD will be "invisible / unnoticed" or "isolated" by the ASM / SSD. In other words, in an OWS scenario, the separation between the SPD and the ASM is re-established as the SPD-FFM separation created by the TWS housing.

[0028] Thus, one aspect of the present invention is the design of a housing for a wearable device, including the placement of the front chamber, front port, rear chamber, rear port, SPD, electronics, battery, and wiring within the rear chamber, and most importantly, the placement of the ASM, which is tuned to produce closely matched front and rear channel frequency responses, both in amplitude and phase, over as wide a frequency band as possible. As used herein, front / rear channels refer to the acoustic propagation paths / channels from the front / rear sides of the SPD to the ASM / SSD.

[0029] In other words, placing an ASM (e.g., 107 / 207) at the nodal plane / position between the front / rear radiation of the SPD can re-establish an important foundation for ANC, ambient pass-through, etc. under OWS operating conditions.

[0030] In one embodiment, the SPD of the present application may be or include an air pulse generating (APG) device as disclosed in U.S. Patent Application Nos. 17 / 553,813, 18 / 321,759, or 19 / 038219, including, but not limited to, 18 / 829,245. This means that the SPD of the present application may generate sound by generating multiple air pulses at an ultrasonic pulse rate.

[0031] The wearable devices 10 and 20 belong to, but are not limited to, a one-microphone (where microphone refers to a microphone, which is a type of SSD) configuration. A wearable device with separation between the SPD and ASM may have a two-microphone configuration.

[0032] For example, Figure 4 is a schematic / conceptual diagram of a wearable device 40 according to one embodiment of the present invention. In addition to (front / rear) ports 403 / 406, wearable device 40 includes a first (ambient) microphone 407a and a second (voice) microphone 407v. The first (ambient) microphone 407a is configured to capture ambient sounds, and the second (voice) microphone 407v is configured to capture the user's voice.

[0033] 5 is a schematic diagram of a wearable device 50 according to one embodiment of the present invention. The appearance of the wearable device 50 (and 20) is borrowed from a commercially available OWS for illustrative purposes only. In addition to the (front / rear) ports 503 / 506, the wearable device 50 includes a first microphone 507a and a second microphone 507v.

[0034] Both microphones 507a and 507v may be positioned according to the same principles as ASM 207 of device 20, i.e., both microphones 507a and 507v may be positioned on the nodal plane or on two separate nodal locations. In addition, the second (voice) microphone 507v may be positioned closer to and / or pointing towards the user's mouth, while the first (ambient) microphone 507a may be positioned further from and / or pointing towards the periphery of the user's mouth.

[0035] If the wearable device 50 has two microphones, the wearable device 50 can incorporate an acoustic beamforming system to extract ambient signals or user voice signals by appropriately combining the signals captured / sensed by the microphones 507a and 507v.

[0036] Referring back to the one-microphone configuration, note that even though the ASM is positioned at a nodal position / plane, there is still a mismatch between the frequency responses or transfer functions of the front and rear channels (or between the forward and rearward radiating waves). For example, FIG. 6(a) shows an amplitude response curve 109F corresponding to the forward radiating wave and an amplitude response curve 108F corresponding to the rearward radiating wave in terms of SPL (sound pressure level) versus frequency, while FIG. 6(b) shows an amplitude response curve 631 of mismatch between the forward and rearward radiating waves. Such mismatch degrades the isolation between the SPD and the ASM and causes stronger SPL leakage from the SPD to the ASM.

[0037] To remedy such mismatch or SPL leakage problems, the wearable device of the present invention may include signal processing circuitry to remove such undesirable mismatch.

[0038] 7 shows a schematic diagram of a signal processing circuit 72 according to one embodiment of the present invention. The signal processing circuit 72 is located within a wearable device 70. The wearable device 70 is similar to the wearable device 10, so like components are designated with like reference numerals. The wearable device 70 is coupled to the ASM / SSD 107 and the SPD 102. The signal processing circuit 72 comprises a discrepancy / residual estimator H2.

[0039] The mismatch estimator H2 is configured to estimate the mismatch between the forward and backward radiated waves generated by the SPD 102 and generate a mismatch estimate 723. The mismatch estimator H2 may correspond to the difference between a first / front transfer function (e.g., having an amplitude response 109F) of the front channel (e.g., channel 109) and a second / back transfer function (e.g., having an amplitude response 108F) of the rear channel (e.g., channel 108). The mismatch estimator H2 generates the mismatch estimate 723 according to the difference between the forward and rear transfer functions and according to a drive signal 724 of the SPD 102.

[0040] It should be noted that the mismatch estimate 723 can be regarded as an SPL leakage from the SPD 102 to the ASM 107. Therefore, the signal processing circuit 720 can subtract / remove the mismatch estimate 723 from the sensed signal 721 from the ASM / SSD 107 to generate a clean ambient signal 722. That is, the signal component corresponding to the sound generated by the SPD 102 (e.g., 723) is removed from the sensed signal 721 from the ASM / SSD 107. Therefore, the anti-ambient block H1 can generate an anti-ambient signal 725 according to the cleaned ambient signal 722, similar to an ANC operation.

[0041] The drive signal 724 may have an anti-ambient signal 725, and the SPD 102 may generate an anti-ambient sound that counters (to the extent possible) the ambient sound AS, so that the listener may perceive clearer music or voice from the intended sound source / signal SS without or with little interference from the ambient sound.

[0042] To visualize the process of generating the propagation of ambient sound (sometimes known as ambient noise) and anti-ambient sound (sometimes known as anti-noise), Figure 8, in one embodiment, shows a diagram illustrating how ambient sound propagates and how anti-ambient sound is generated, with the same notation carried over from the previous figure.

[0043] In FIG. 8, the source of the ambient sound AS is assumed to be far from the wearable device (e.g., the OWS earphone shown in FIG. 8), so the ambient sound AS is assumed / illustrated as a plane wave.

[0044] As shown, ambient sound AS may propagate through (primary) acoustic channel P to the vicinity of eardrum 810. Alternatively, ambient sound AS may be received by a microphone and processed by an amplifier / filter, an ADC (analog-to-digital converter), an ambient controller (as part of the signal processing circuit), a DAC (digital-to-analog converter), an amplifier Amp, an SPD driver, and an SPD to generate anti-ambient sound or anti-noise. The anti-ambient sound or anti-noise may pass through (secondary) acoustic channel S to reach the vicinity of eardrum 810. Ideally, the noise (from the ambient) and the anti-noise (from the SPD) cancel each other out, allowing the listener to enjoy music without being interfered with by ambient noise / sound.

[0045] FIG. 9 provides a system 90 as an analytical block diagram illustrating the signal processing chain of FIG. 8, where MA represents the microphone / ASM / SSD transfer function and H A represents the lumped transfer function of the front-end amplifier / filter, and H C where A represents the transfer function of the ambient controller 902, A represents the aggregate transfer function of the output amplifier, SPD driver, and SPD, and P / S represents the transfer function of the primary / secondary acoustic channels. Ideally, the ambient controller 902 has N O =[P+S·A·H C ·H0·M A ]N I →0 (Equation 1)C In Equation 1, N1 mathematically denotes the input noise of the system 90, which is the ambient noise AS. N0 mathematically denotes the output noise of the system 90, which is the (residual) noise in the ear canal or near the eardrum 810 after ambient and anti-ambient noise cancellation. In the current analysis, the transfer functions of the ADC and DAC are assumed to be aggregated for simplicity, and H0=H A H ADC H DAC can be the aggregated transfer function that takes into account the front-end amplifier, ADC, and DAC. Ideally, the ambient controller transfer function H C is H C =-[P / (S·A·H0·M A )] (Equation 2).

[0046] It should be noted that the rectangular blocks shown in Figure 8 represent acoustic transducers and electrical circuits embedded within the wearable device, and that the electrical circuits shown in Figure 8 comprise or may be considered to be signal processing circuits. In one embodiment, the wearable device of the present invention may comprise a signal processing circuit 900 shown in Figure 9, which comprises a front-end amplifier H A , ADC, DAC, and importantly, the ambient controller 902.

[0047] In this application, a function block and its transfer function may share the same notation, which means that the notation of a transfer function may (but not always) be used to denote the corresponding function block.

[0048] It should be noted that the acoustic feedback path / channel from the SPD to the ASM / SSD has been omitted in Figures 8 and 9 for simplicity. For completeness, in addition to Figures 8 and 9, a front channel Ff from the front of the SPD to the ASM / SSD and a rear channel Fb from the rear side of the SPD to the ASM / SSD have been incorporated in Figures 10 and 11(a), as shown in Figures 10 and 11(a).

[0049] Assuming that the forward and backward radiation waves (radiated from the SPD) have substantially equal amplitudes and opposite polarities, the system 92 shown in FIG. 11(a) can be derived as the system 94 shown in FIG. 11(b), where the feedback path F is the difference between the transfer functions corresponding to the front and rear channels, F=F f -F b It can be expressed as:

[0050] Assume that the transfer function of the controller can be found as Equation 2, and the system 94 shown in Figure 11(b) can be derived as the system 96 shown in Figure 11(c). In this case, the noise N I , N C , N O are expressed as the following equations 1 (equation 3) and 2 (equation 4).

[0051]

number

[0052]

number

[0053] Note that the acoustic means to separate the ASM from the SPD (place the ASM at the nodal position) is ideally to achieve F → 0 (mathematically) from Equation 4, and therefore NO → 0.

[0054] In practice, F → 0 may not be perfectly realizable: if F ≠ 0, this means significant mismatch / disparity between the (transfer functions of) the front and rear channels, and feedback paths / blocks may be further included in the perimeter controller.

[0055] For example, Figure 12(a) shows a perimeter controller A42 with a feedback loop having a forward block with transfer function H C and a feedback block with transfer function F D. The transfer function H C can be determined via Equation 2. d is FΔ →0, where the system A4 shown in FIG. 12(a) has a feedback path F Δ =FF da 12(b) with F da is F d In other words, F Δ →0 such that the transfer function F d In one embodiment, it is possible to select a feedback block having F d is F d =(A H0 M A ).F da or F d =(A·H 0· M A )·F can be selected.

[0056] F for F≠0 Δ → If 0 is desired, F da →F so that F d can be designed, where F=F f -F b This is the transfer function F d A feedback block with transfer function F f and the transfer function F b It means relating to the difference between

[0057] Note that Fig. 12(a) shows a similar concept to Fig. 7. The forward block HC in the periphery controller A42 shown in Fig. 12(a) may be similar to the anti-periphery block H1 shown in Fig. 7. The feedback block F shown in Fig. 12(a) d may be similar to the discrepancy estimator H2 shown in Figure 7. The feedback block F d The output of the sound sensing device M may be similar to the discrepancy estimate 723 of FIG. 7. The subtractor A44 included in the ambient controller A42 of FIG. 12(a) A The sensing signal from the feedback block F d and may be similar to the subtraction operation performed by signal processing circuitry 72. Signal 722 corresponds to the output of subtractor A44.

[0058] Whether it is the feedback block Fd in FIG. 12(a) or the mismatch estimator H2 in FIG. 7, the difference (information) of the transfer functions corresponding to the front and rear channels, e.g., F=F f -F b It is important to obtain

[0059] In brief, the signal processing circuit of the present invention obtains the difference between the transfer functions corresponding to the front and rear channels, and outputs, for example, a mismatch estimate 723 (or similarly / equivalently, a feedback block F in the ambient controller A42) from the sensed signal 721. d By subtracting / removing the output of the SPD (output of the SPD), the sound signal component corresponding to the sound generated by the SPD can be reduced.

[0060] Furthermore, the front and rear channels depend not only on the housing design, but also on hairstyle, earrings, eyeglasses worn that day, and how the earphones are attached at the time. Because many variations can occur, recalibration may be desirable to maintain optimal environmental control performance.

[0061] One embodiment may include using calibration test signals / tones (such as a series of log frequency sweeps of various durations and amplitudes) to refine the (factory) curve of the mismatch response 631. Such a recalibration process may occur automatically whenever the device is detected "in ear" (such as by a proximity sensor), or may occur manually at the user's direction (via touch, voice, or APP control).

[0062] In other words, for recalibration, the signal processing circuitry may be controlled (e.g., by a controller) to obtain a differential transfer function. Additionally, the wearable device may optionally include a sensor (e.g., sensor 74 in wearable device 70) configured to detect whether the wearable device (e.g., 70) is worn by a user. In one embodiment, sensor 74 may be a proximity sensor.

[0063] Referring back to the two-microphone configuration, instead of removing the residuals, an equalization operation may be performed on the sensed signal to reduce the sound signal component from the sensed signal and generate a clean ambient signal.

[0064] For example, Figure 13 shows a schematic diagram of a wearable device B1 including a signal processing circuit B0 according to one embodiment of the present invention. The signal processing circuit B0 is coupled to an ambient / first microphone B07a and a voice / second microphone B07v to receive first and second sensed signals from the microphones B07a and B07v. The signal processing circuit B0 is mathematically k v The block B22 is represented by Amic+k v ·Vmic=0 or ||Amic+k v The SPD is designed to minimize ||·Vmic|| as much as possible, where ||·|| may represent or correspond to the energy or norm of the input arguments. In this interpretation, Amic and Vmic may be interpreted as the sensed signals sensed by the ambient microphones and the voice microphone, respectively. In another interpretation, Amic and Vmic may represent the transfer functions from the SPD to the ambient microphones and the voice microphone, respectively.

[0065] In one embodiment, k v is k v= -Vmic / Amic (Equation 5) (herein, the slash symbol " / " refers to "division"), and the transfer function Vmic / Amic can be found by a "system identification" tool via simulation software such as MATLAB® (herein, the slash symbol " / " refers to "or"). In one embodiment, k v may be optimized over a frequency band of interest, for example, but not limited to, 20-8 kHz.

[0066] In the embodiment shown in FIG. 13, block B22 or k v Note that V is applied to Vmic. v can also be applied to Amic, but is not limited to this.

[0067] In one embodiment, the signal processing circuit B0 may perform a subtraction operation on the sensed signal to capture the voice signal, e.g., perform Vmic-Amic. The principles behind capturing voice by subtraction are: 1) ambient sound A S, which is generally far-field, tends to generate nearly identical outputs from B07a and B07v, and therefore such signals tend to largely cancel each other out through subtraction; 2) the voice V C emitted by the user is near-field, i.e., has an intensity ∝1 / r. Assuming that B07v is closer to and points toward the user's mouth, while B07a is farther from and points away from the user's mouth, this SPL ∝1 / r will cause B07v to generate a higher output in response to V C than B07a, and the subtraction will leave a significant portion corresponding to the voice V C.

[0068] Transfer function k v Referring again to equation 5 or block B22 having: it may be beneficial to obtain a ratio of the transfer functions between the transfer function Vmic and the transfer function Amic, and the equalization operation is performed according to the ratio Vmic / Amic.

[0069] In other words, in a two-microphone configuration, the signal processing circuit of the present invention obtains a ratio of the transfer functions, for example, Vmic / Amic, and performs a signal processing on one of the sensed signals (for example, transfer function k v An equalization operation may be performed (eg, by block B22 having the same signal level) and the equalized signal (eg, the output of block B22) may be combined with the other sensed signal to reduce the sound signal component.

[0070] In one embodiment, block B22, the ambient controller (including the forward block HC and the feedback block Fd), the difference estimator H2, and the anti-ambient block H1 may be realized by, but are not limited to, digital IIR (infinite impulse response) filters.

[0071] The above description is also applicable to environmental control of smart glasses, where the same SPD-microphone separation problem exists. The smart glasses in this application have functionality in addition to simple optical functionality. For example, the smart glasses may have electronic devices embedded therein to perform audio / video related operations.

[0072] For example, Figure 14 shows a schematic diagram of a wearable device C0 according to one embodiment of the present invention. Wearable device C0 may include an SPD C02, ports C03 and C06, and microphones C07a and C07v. In the embodiment shown in Figure 14, port C03 may function as a front port and is typically located at a location with the shortest distance to the opening of the ear canal, port C06 may function as a rear port and is located near the temple hinge / mount to maximize low-frequency (e.g., <100 Hz) frequency response, microphone C07v (for capturing the user's voice) may be one-quarter of the distance from rear port C06 to front port C03, and microphone C07a (for capturing the user's ambient sound) may be located above port C03 and / or near the end of the temple straight port, but is not limited to such locations.

[0073] In one embodiment, microphones C07a, C07v may be placed at nodal positions.

[0074] In one embodiment, the wearable device C0 may include the signal processing circuit described above to reduce sound signal components corresponding to sounds generated by the SPD from the sensing signal sensed by the microphone.

[0075] In essence, the present invention provides SPD-SSD or SPD-ASM isolation: acoustic means of placing microphones at nodal locations and electrical means of reducing sound signal components from the sensed signal are provided to produce a clean ambient signal that does not contain components corresponding to the sound generated by the SPD.

[0076] Those skilled in the art will readily observe that numerous modifications and variations of the apparatus and method may be made while retaining the teachings of the present invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims. [Explanation of symbols]

[0077] 10: Wearable devices 105: Housing 102: Sound generating device (SPD)

Claims

1. a sound generating device and a sound sensing device; the sound generating device generates a sound and generates a forward radiation wave and a backward radiation wave; The sound sensing device is disposed at a node position, and the forward radiation wave and the backward radiation wave cancel each other out at the node position. Wearable device.

2. a first port and a second port; the forward radiation wave propagates outward through the first port and the backward radiation wave propagates outward through the second port; The wearable device of claim 1 .

3. a first frequency response corresponding to the forward radiation wave received at the sound sensing device and a second frequency response corresponding to the rearward radiation wave received at the sound sensing device are matched; The wearable device of claim 1 .

4. a first sound sensing device disposed at a first nodal location; a second sound sensing device disposed at a second nodal location; At the first and second node positions, the forward radiation wave and the backward radiation wave cancel each other out. The wearable device of claim 1 .

5. the first sound sensing device is configured to receive voice from a user; the second sound sensing device is configured to receive ambient sound from the surroundings; The wearable device of claim 4 .

6. the wearable device emits the sound toward an open field when the user wears the wearable device; The wearable device of claim 1 .

7. The wearable device is an earphone or a smart glass. The wearable device of claim 1 .

8. the sound generating device comprises an air pulse generator; the sound-generating device generates the sound by generating a plurality of air pulses at an ultrasonic pulse rate; The wearable device of claim 1 .

9. a sound generating device, a sound sensing device, and a signal processing circuit; the signal processing circuit receives a sensing signal generated by the sound sensing device; the signal processing circuitry performs operations on the sensed signal to generate a clean ambient signal; the operation is configured to reduce a sound signal component corresponding to a sound generated by the sound generation device. Wearable device.

10. the wearable device emits the sound toward an open field when the user wears the wearable device; The wearable device of claim 9 .

11. the signal processing circuit removes the sound signal component from the sensed signal to generate the clean ambient signal. The wearable device of claim 9 .

12. the signal processing circuitry comprises a mismatch estimator; the mismatch estimator is configured to estimate a mismatch between forward and backward radiated waves generated by the sound generation device and generate a mismatch estimate. The wearable device of claim 9 .

13. the signal processing circuit subtracts the mismatch estimate from the sensed signal to generate the clean ambient signal. The wearable device of claim 12.

14. the mismatch estimator generates the mismatch estimate in response to a drive signal of the sound generating device. The wearable device of claim 12.

15. the mismatch estimator corresponds to a transfer function that is related to the difference between a first transfer function and a second transfer function; the first transfer function corresponds to a front channel from a front side of the sound generating device to the sound sensing device; the second transfer function corresponds to a rear channel from the rear side of the sound generating device to the sound sensing device. The wearable device of claim 12.

16. the signal processing circuit comprises an anti-periphery block; the anti-ambient block generates an anti-ambient signal according to the clean ambient signal; the driving signal of the sound generating device includes the anti-ambient signal; The wearable device of claim 9 .

17. the signal processing circuit includes a feedback loop having a forward block and a feedback block; the feedback block has a transfer function related to the difference between the first transfer function and the second transfer function; the first transfer function corresponds to a front channel from a front side of the sound generating device to the sound sensing device; the second transfer function corresponds to a rear channel from the rear side of the sound generating device to the sound sensing device. The wearable device of claim 9 .

18. the signal processing circuit includes a subtractor; the subtractor subtracts the output from the feedback block from the sensing signal from the sound sensing device; 18. The wearable device of claim 17.

19. a first sound sensing device that generates a first sensing signal; a second sound sensing device that generates a second sensing signal; The wearable device of claim 9 .

20. the signal processing circuit performs an equalization operation on the first sensed signal and the second sensed signal to reduce the sound signal component and generate the clean ambient signal.

20. The wearable device of claim 19.

21. the signal processing circuit performs a subtraction operation on the first sensed signal and the second sensed signal to capture a voice signal; 20. The wearable device of claim 19.

22. the signal processing circuit determines a differential transfer function between the first transfer function and the second transfer function; the first transfer function corresponds to a front channel from a front side of the sound generating device to the sound sensing device; the second transfer function corresponds to a rear channel from the rear side of the sound generating device to the sound sensing device. The wearable device of claim 9 .

23. the signal processing circuit is controlled to obtain the differential transfer function; 23. The wearable device of claim 22.

24. a sensor configured to detect whether the wearable device is worn by a user; The signal processing circuit determines the differential transfer function when the sensor detects that the wearable device is being worn.

24. The wearable device of claim 23.

25. the signal processing circuit includes a digital infinite impulse response (IIR) filter; The wearable device of claim 9 .

26. the sound generating device comprises an air pulse generator; the sound-generating device generates the sound by generating a plurality of air pulses at an ultrasonic pulse rate; The wearable device of claim 9 .

27. A signal processing method applied to a signal processing circuit disposed in a wearable device, comprising: receiving a sensing signal from a sound sensing device disposed within the wearable device; performing an operation on the sensed signal to reduce sound signal components corresponding to sounds generated by a sound generating device disposed within the wearable device to generate a clean ambient signal; A signal processing method in which the wearable device emits the sound toward an open field when a user wears the wearable device.

28. performing the operation on the sensed signal to mitigate the sound signal component, determining a differential transfer function between the first transfer function and the second transfer function; obtaining a mismatch estimate according to the differential transfer function and a drive signal of the sound generating device; removing the mismatch estimate from the sensed signal to generate the clean ambient signal; the first transfer function corresponds to a front channel from a front side of the sound generating device to the sound sensing device; 28. The signal processing method of claim 27, wherein the second transfer function corresponds to a rear channel from a rear side of the sound generating device to the sound sensing device.

29. performing the operation on the sensed signal to mitigate the sound signal component, receiving a first sensing signal from a first sound sensing device and a second sensing signal from a second sound sensing device; performing an equalization operation on the first sensed signal to generate an equalized signal; 28. The signal processing method of claim 27, further comprising: attenuating the tonal signal components according to the equalized signal.

30. performing the operation on the sensed signal to mitigate the sound signal component, Obtaining a transfer function ratio between the first transfer function and the second transfer function; receiving a first sensing signal from a first sound sensing device and a second sensing signal from a second sound sensing device; performing an equalization operation on the first sensed signal according to the ratio of the transfer functions to generate an equalized signal; combining the equalized signal with the second sensed signal to reduce the sound signal component; the first transfer function corresponds to a first channel from the sound generating device to the first sound sensing device; 28. The signal processing method of claim 27, wherein the second transfer function corresponds to a second channel from the sound generating device to the second sound sensing device.

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