Wearable device and signal processing method

Abstract

A wearable device includes a sound generating device and a sound sensing device. The sound generating device produces a forward radiating wave and a backward radiating wave when emitting sound. The sound sensing device is positioned at a node location where the forward radiating wave and the backward radiating wave cancel each other out.

Description

[Technical Field]

[0001] This application refers to a wearable device and a signal processing method, and more particularly to a wearable device and signal processing method that can establish isolation between a sound generating device and an environmental sensing microphone. [Previous Technology]

[0002] In recent years, a new type of true wireless earbud has gradually emerged.

[0003] In the previous generation of true wireless (also known as true wireless stereo, TWS) earbuds, the usual practice was to insert the tip of the silicone / foam-covered sound tube into the listener's ear canal to create a semi / completely enclosed space between the sound producing driver / device (SPD) of the true wireless earbuds and the listener's eardrum.

[0004] This approach can achieve two effects: 1) Improved bass performance; 2) Isolation of the environment from the ear canal.

[0005] In contrast to traditional true wireless earbuds, this new type of "open-ear" true wireless (also known as open-ear stereo (OWS)) earbuds features an unobstructed opening in the ear canal, allowing air to freely enter and exit. These open-ear earbuds are generally well-received for their greater comfort and more natural sound, allowing users to better perceive their surroundings. Furthermore, because air can naturally flow in and out of the ear, they are less tiring than previous generations of true wireless earbuds. Therefore, users can wear them for extended periods without experiencing physical discomfort or subconscious / mental imbalance due to sound isolation.

[0006] One of the major technological advancements in non-open-fit / closed-back true wireless earbuds is the concept of Active Noise Cancelling (ANC) and Intelligent Ambient Passthrough (or generally referred to as Ambient Control (AC)).

[0007] In closed-back true wireless earbuds, the earbud shell and (foam or silicone-coated) earbud tip divide the space around the listener's ear into three parts: 1) the front cavity of the sound generating driver / device plus the listener's ear canal; 2) the rear cavity of the sound generating driver / device, which contains various components inside the earbud shell, such as sub-components of the sound generating driver / device, electronic components, batteries, etc.; 3) the outer periphery of the earbud shell.

[0008] In these closed-back true wireless earbuds, active noise cancellation is typically controlled by two types of microphones (also known as sound sensing devices (SSDs)): 1) a feedforward microphone (FFM) for sensing sound outside the earbuds to provide a signal about ambient sound on the feedforward signal path; and 2) a feedback microphone (FBM) for sensing sound in the front cavity plus the ear canal space to provide a signal about the result of active noise cancellation on the feedback signal path (i.e., ambient noise remaining in the front cavity plus the ear canal).

[0009] In the above configuration, through the aforementioned three subdivided parts, the shell of the closed true wireless earbuds isolates not only the feedforward microphone and the sound generated by the earbuds' own sound generation driver / device, but also the feedback microphone and ambient sound.

[0010] In other words, in closed-back true wireless earbuds, three parts are created by using the earbud shell: the feedforward microphone is largely isolated (or ignored) from the sound produced by the earbuds, while the feedback microphone is largely isolated (or ignored) from ambient sound outside the earbuds. These two states of "isolation" or "ignoring" are the key foundation for achieving the powerful active noise cancellation of closed-back true wireless earbuds.

[0011] However, in open-back earbuds, the space is no longer subdivided in the same way to achieve the aforementioned isolation (as in true wireless earbuds), and any microphone can detect the sound generated by the sound-generating driver / device of the open-back earbuds. As a result, the feedforward microphone can no longer distinguish between ambient sound and the sound generated by the sound-generating driver / device of the open-back earbuds themselves; and the feedback microphone cannot monitor the results of active noise cancellation / ambient control without interference from ambient sound. This means that the new open-back earbuds no longer have the basis to support the active noise cancellation / ambient control functions found in closed-back true wireless earbuds.

[0012] Therefore, how to provide isolation between the sound generating device and the environmental sensing microphone for active noise cancellation or environmental control in open wearable scenarios is an important goal in this field. [Summary of the Invention]

[0013] Therefore, the main purpose of this application is to provide isolation between the sound generating device and the environmental sensing microphone in order to improve the shortcomings of the prior art.

[0014] One embodiment of this application provides a wearable device, which includes a sound generating device and a sound sensing device. The sound generating device generates a forward radiating wave and a backward radiating wave when emitting sound. The sound sensing device is disposed at a node position, where the forward radiating wave and the backward radiating wave cancel each other out.

[0015] One embodiment of this application provides a wearable device, which includes 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 circuit performs an operation on the sensing signal and generates a clean environment signal. The operation is used to reduce a sound signal component corresponding to the sound emitted by the sound generating device.

[0016] One embodiment of this application provides a signal processing method for a signal processing circuit disposed within a wearable device. The signal processing method includes the following steps: receiving a sensing signal from a sound sensing device disposed within the wearable device; and performing an operation on the sensing signal to reduce a sound signal component, the sound signal component corresponding to a sound emitted by a sound generating device disposed within the wearable device, and generating a clean environment signal; wherein, when a user wears the wearable device, the wearable device emits sound toward an open area.

Implementation Method

[0018] In order to provide active noise cancellation (ANC) or ambient control (AC), an ambient sensing microphone (ASM) is required to acquire the sound of the surrounding environment. In this application, ambient control generally refers to the technology of controlling / managing the ambient sound perceived by the listener / user.

[0019] One of the purposes of this application is to establish isolation between a sound producing device (SPD) and an environmental sensing microphone (which is a sound sensing device), so that the active noise cancellation / environmental control module can obtain a clean ambient sound that does not contain sound / signal components corresponding to the sound emitted by the sound producing device, or reduce or minimize the sound / signal components corresponding to the sound emitted by the sound producing device in the clean ambient sound as much as possible.

[0020] In this application, the isolation between the sound generating device and the environmental sensing microphone can be established through acoustic and / or electrical means. Acoustically, the environmental sensing microphone can be positioned at a node where the forward and backward radiated waves of the sound generating device cancel each other out. Electrically, a signal processing operation can be performed on the sound / signal sensed by the environmental sensing microphone to reduce / minimize the sound / signal components corresponding to the sound emitted by the sound generating device, thereby obtaining a clean environmental sound / signal. Preferably, both acoustic and electrical methods can be used, but this is not a limitation.

[0021] Figure 1 is a schematic diagram of a wearable device 10 according to an embodiment of the present invention. The wearable device 10 includes a housing 105, a sound generating device 102, and a sound sensing device (SSD) 107, wherein the sound sensing device 107 can serve as an environmental sensing microphone to capture ambient sound. The sound generating device 102 can divide the internal space of the wearable device 10 into a front cavity 101 and a rear cavity 104. A front end 103 and a rear end 106 are formed on the housing 105. The rear cavity 104 is used to accommodate the device's electronic components, battery, and wiring. The wearable device 10 can be an open-wear style or open-wearable stereo (OWS) earphone, that is, the design of the wearable device 10 is such that when the user wears the wearable device 10, the wearable device 10 will emit sound into a fairly open or wide field, rather than a closed ear canal. While emitting sound, the sound generating device 102 generates a forward radiating wave that passes through a front end 103 via a front channel 109 and a backward radiating wave that passes through a rear end 106 via a rear channel 108. It should be noted that the forward and backward radiating waves usually have similar or the same amplitude but opposite polarities.

[0022] In this application, the emission of sound from a wearable device into an open field can generally be understood as follows: when a user wears the wearable device, the sound outlet (as shown in Figure 1, front end 103 / rear end 106) is a certain distance (as shown in D103 / D106) from an ear canal 110 in the sound propagation path. This means that the sound emitted from the sound outlet will pass through an open or relatively open space before reaching the ear canal (as shown in 110). Here, "relatively open" means "unobstructed". In other words, the emission of sound from a wearable device into an open field can also generally be interpreted as the sound radiation path / channel between the sound outlet and the ear canal 110 not being blocked / closed. In this case, the forward / backward radiation waves generated by the sound generating device can be (significantly) captured by the sound sensing device / environmental sensing microphone of the wearable device.

[0023] In order to alleviate / bypass the problem of environmental sound being polluted by sound generated by the sound generating device, the sound sensing device 107 (as an environmental sensing microphone) can be set at a node surface or node position, and the forward and backward radiated waves can cancel each other out or be unaffected at this node surface or node position.

[0024] For example, Figure 2 illustrates a schematic diagram of a commercial open-type wearable device 20 worn on the ear. The wearable device 20 has a front end 203 and a rear end 206, and 210 represents the ear canal. Using a simulation tool such as COMSOL, Figure 3 illustrates the sound energy distribution of forward and backward radiating waves (for example, at 1.5 kHz) in the space surrounding the wearable device 20 based on a specific front end / rear end position.

[0025] The darkness / brightness in Figure 3 represents the intensity of sound energy. The darker an area is, the stronger the sound energy on it, regardless of its polarity. The right half of Figure 3 is dominated by forward radiation waves, and the left half is dominated by backward radiation waves. As can be seen from Figure 3, the bright band between the left and right parts represents the nodal surface. There is little or no sound energy on the nodal surface because the forward and backward radiation waves cancel each other out on the nodal surface (which is the set of nodal locations).

[0026] It can be deduced from the above description that when the nodal plane is formed in an ideal state (i.e., it does not move with frequency) and the ambient sensing microphone / sound sensing device is accurately located on this plane, the sound waves emitted by the sound generating device will produce 0 (no) or close to 0 (almost none) output on the ambient sensing microphone / sound sensing device. That is, the sound emitted by the sound generating device becomes "invisible / negligible" or "isolated" from the ambient sensing microphone / sound sensing device. In other words, in the open wearable scenario, the isolation between the sound generating device and the ambient sensing microphone will be re-established, just like the isolation between the sound generating device and the feedforward microphone established by the shell of a True Wireless Stereo (TWS) device.

[0027] Therefore, one aspect of the present invention is the design of a housing for a wearable device, including a front cavity, a front end, a rear cavity, a rear end, a sound generating device inside the rear cavity, electronic components, a battery and circuitry, and most importantly, an ambient sensing microphone, which can be adjusted to generate frequency responses of the front and rear channels that are as closely matched in amplitude and phase as possible over the widest possible frequency band, where the front / rear channel refers to the sound propagation path / channel from the front / rear sound generating device to the ambient sensing microphone / sound sensing device.

[0028] In other words, "placing the ambient sensing microphone (such as 107 / 207) on the nodal surface / position between the front / rear radiation of the sound generating device" can re-establish an important foundation for active noise cancellation, ambient direct access, etc. under open wearable operating conditions.

[0029] In one embodiment, the sound generating device of this application may be, or includes, the air pulse generating device disclosed in U.S. Patent Application Nos. 17 / 553,813, 18 / 321,759, or 18 / 829,245, but is not limited thereto. This means that the sound generating device of this application can emit sound by generating a plurality of air pulses at an ultrasonic pulse rate.

[0030] Wearable devices 10 and 20 are configured with a single microphone (here, a microphone represents a sound sensing device), but are not limited thereto. Wearable devices that can isolate the sound generating device and the ambient sensing microphone may also have a dual-microphone configuration.

[0031] For example, Figure 4 is a schematic / conceptual diagram of a wearable device 40 according to an embodiment of the present invention. In addition to the (front / rear) endpoints 403 / 406, the wearable device 40 also includes a first (ambient) microphone 407a and a second (voice) microphone 407v. The first (ambient) microphone 407a is configured to capture ambient sound, and the second (voice) microphone 407v is configured to capture the user's voice.

[0032] In fact, Figure 5 is a schematic diagram of a wearable device 50 according to an embodiment of the present invention. The appearance of the wearable device 50 (and 20) is inspired by commercially available open-back wearable headphones and is used for illustrative purposes only. In addition to the (front / rear) endpoints 503 / 506, the wearable device 50 also includes a first microphone 507a and a second microphone 507v.

[0033] Both microphones 507a and 507v can be configured based on the same principle as the environmental sensing microphone 207 of the wearable device 20, that is, both microphones 507a and 507v can be set on the node surface or at two different node positions. In addition, the second (voice) microphone 507v can be set closer to and / or pointed towards the user's mouth; while the first (environmental) microphone 507a can be set further away from the user's mouth and / or pointed towards the surrounding environment.

[0034] Given that the wearable device 50 has two microphones, the wearable device 50 can be combined with an acoustic beamforming system to capture / sensor environmental signals or user voice signals by appropriately combining the signals captured / sensed by microphones 507a and 507v.

[0035] Please refer back to the single microphone configuration. Note that even if the ambient sensing microphone is located at a node position / plane, there are still differences in the frequency response or transfer function between the front and rear channels (or between the forward and backward radiated waves). For example, Figure 6(a) shows the amplitude response curve 109F corresponding to the forward radiated wave and the amplitude response curve 108F corresponding to the backward radiated wave in the form of sound pressure level (SPL) versus frequency; Figure 6(b) shows the amplitude response curve 631 showing the difference between the forward and backward radiated waves. This difference reduces the isolation between the sound generating device and the ambient sensing microphone, resulting in greater sound pressure level leakage from the sound generating device to the ambient sensing microphone.

[0036] In order to compensate for this difference or sound pressure level leakage, the wearable device of the present invention may include a signal processing circuit to eliminate this unwanted difference.

[0037] Figure 7 illustrates a schematic diagram of a signal processing circuit 72 according to an embodiment of the present invention. The signal processing circuit 72 is disposed within a wearable device 70. The wearable device 70 is similar to the wearable device 10, therefore, the same components are represented by the same symbols. The wearable device 70 is coupled to an environmental sensing microphone / sound sensing device 107 and a sound generating device 102. The signal processing circuit 72 includes a difference (residual) estimation unit H2.

[0038] The difference estimation unit H2 is used to estimate the difference between the forward and backward radiated waves generated by the sound generating device 102 and generate a difference estimate 723. The difference estimation unit H2 may correspond to the difference between a first / front transfer function (e.g., having an amplitude response 109F) of one of the front channels (e.g., channel 109) and a second / back transfer function (e.g., having an amplitude response 108F) of one of the rear channels (e.g., channel 108). The difference estimation unit H2 generates the difference estimate 723 based on the difference between the front and back transfer functions and based on a drive signal 724 of the sound generating device 102.

[0039] It is worth noting that the difference estimate 723 can be considered as the sound pressure level leakage from the sound generating device 102 to the ambient sensing microphone 107. Therefore, the signal processing circuit 720 can subtract / remove the difference estimate 723 from a sensing signal 721 from the ambient sensing microphone / sound sensing device 107 to generate a clean ambient signal 722. That is, the signal component (such as 723) corresponding to the sound emitted by the sound generating device 102 is removed from the sensing signal 721 from the ambient sensing microphone / sound sensing device 107. Therefore, similar to active noise cancellation, an anti-ambient block H1 can generate an anti-ambient signal 725 based on the clean ambient signal 722.

[0040] The drive signal 724 may include an ambient-resistant signal 725, and the sound generating device 102 may generate an ambient-resistant sound to (as far as possible) cancel an ambient sound AS. Therefore, the listener can perceive clearer music or speech from the predetermined sound source / signal SS, free from or less affected by interference from the surrounding environment.

[0041] In order to illustrate the process of the propagation of ambient sound (which may be referred to as ambient noise) and the generation of anti-ambient sound (which may be referred to as anti-noise), Figure 8 illustrates, as an embodiment, a schematic diagram of how ambient sound propagates and how anti-ambient sound is generated, and this figure inherits the same symbols from the previous illustrations.

[0042] In Figure 8, since the source of the ambient sound AS is assumed to be at a distance from the wearable device (such as the open-fit earphone in Figure 8), the ambient sound AS is assumed / displayed as a plane wave.

[0043] As shown in the figure, ambient sound AS can propagate to the vicinity of eardrum 810 through a (primary) acoustic channel P. In other words, ambient sound AS can be received by a microphone and processed by an amplifier / filter, an analog-to-digital converter (ADC), an environmental controller (as part of the signal processing circuit), a digital-to-analog converter (DAC), an amplifier Amp, a sound generation device driver, and a sound generation device to generate an anti-ambient sound or anti-noise. This anti-ambient sound or anti-noise can reach the vicinity of eardrum 810 through a (secondary) acoustic channel S. Ideally, the noise (from the environment) and the anti-noise (from the sound generation device) can cancel each other out, and the listener can enjoy the music without being disturbed by ambient noise / sound.

[0044] Figure 9 provides an analysis block diagram of a system 90 to show the signal processing chain in Figure 8, where MA represents the transfer function of the microphone / ambient sensing microphone / sound sensing device, HA represents the overall transfer function of the front-end amplifier / filter, HC represents the transfer function of an ambient controller 902, A represents the overall transfer function of the output amplifier, sound generation device driver, and sound generation device, and P / S represents the transfer function of the primary / secondary acoustic channels. Ideally, the ambient controller 902 may have a transfer function HC such that NO = [P + S∙A∙HC∙H0∙MA] NI → 0 (Equation 1). In Equation 1, NI mathematically represents the input noise of system 90, i.e., ambient noise AS. NO mathematically represents the output noise of system 90, which is the (residual) noise in the ear canal or near the eardrum 810 after the ambient noise and anti-ambient noise are canceled out. In the current analysis, for simplicity, the transfer functions of the analog-to-digital converter and the digital-to-analog converter are assumed to be integrated, and H0 = HAHADCHDAC can be considered as the overall transfer function taking into account the front-end amplifier, the analog-to-digital converter, and the digital-to-analog converter. Ideally, the transfer function HC of the environmental controller can be chosen as HC = - [P / (S∙A∙H0∙MA)] (Equation 2).

[0045] It is worth noting that the rectangular blocks shown in Figure 8 represent the acoustic transducers and circuitry embedded in the wearable device, and the circuitry in Figure 8 may include or be considered as signal processing circuitry. In one embodiment, the wearable device of the present invention may include a signal processing circuitry 900 as shown in Figure 9, wherein the signal processing circuitry 900 may include a front-end amplifier HA, an analog-to-digital converter, a digital-to-analog converter, and, most importantly, an environmental controller 902.

[0046] In this application, functional blocks and their transfer functions sometimes share the same symbol, that is, sometimes (but not always) the symbol of the transfer function is used to represent the corresponding functional block.

[0047] It is worth noting that, for the sake of simplicity, the acoustic feedback path / channel from the sound generating device to the ambient sensing microphone / sound sensing device is omitted in Figures 8 and 9. For the sake of completeness, as shown in Figures 10 and 11, in addition to the contents of Figures 8 and 9, the front channel Ff from the front of the sound generating device to the ambient sensing microphone / sound sensing device and the rear channel Fb from the rear of the sound generating device to the ambient sensing microphone / sound sensing device are also included in Figures 10 and 11(a).

[0048] Assuming that the forward and backward radiating waves (emitted from the sound generating device) have substantially equal amplitudes and opposite polarities, the system 92 shown in Figure 11(a) can be used to derive the system 94 shown in Figure 11(b), where the feedback path F can be expressed as F = Ff - Fb, which corresponds to the difference in the transfer functions of the front and rear channels.

[0049] Assuming the transfer function of the controller can be obtained from Equation 2, the system 94 shown in Figure 11(b) can be derived from the system 96 shown in Figure 11(c). In this case, the noise NI, NC and NO in Figure 11 can be expressed as (Equation 3) and (Equation 4).

[0050] It is worth noting that the acoustic method used to isolate the environmental sensing microphone from the sound generating device (setting the environmental sensing microphone at the node position) is to achieve F→0 (mathematically). Therefore, ideally, NO→0 can be obtained according to Equation 4.

[0051] In reality, F→0 may not be perfectly achieved. When F≠0, it indicates a significant mismatch / difference between the front and rear channels (transfer functions), while the environmental controller contains an additional feedback path / block.

[0052] For example, Figure 12(a) illustrates an environmental controller A42, which includes a feedback loop having a feedforward block with a transfer function HC and a feedback block with a transfer function Fd. The transfer function HC can be obtained through Equation 2. The transfer function Fd can be selected such that FΔ→0, where system A4 shown in Figure 12(a) is equivalent to system A6 shown in Figure 12(b) with a feedback path FΔ= F - Fda, and Fda is related to Fd. In other words, the feedback block with transfer function Fd can be selected such that FΔ→0. In one embodiment, Fd can be selected as Fd= (A∙H0∙MA)∙Fda or Fd= (A∙H0∙MA)∙F.

[0053] If F≠0, it is necessary to make FΔ→0, then Fd can be designed to make Fda→F, where F = Ff- Fb. This means that the feedback block with transfer function Fd should be related to the difference between transfer function Ff and transfer function Fb.

[0054] It is worth noting that Figure 12(a) illustrates a concept similar to that in Figure 7. The feedforward block HC of the environmental controller A42 shown in Figure 12(a) can be analogized to the anti-environment block H1 in Figure 7; the feedback block Fd shown in Figure 12(a) can be analogized to the difference estimation unit H2 in Figure 7; the output of the feedback block Fd shown in Figure 12(a) can be analogized to the difference estimate 723 in Figure 7; the subtractor A44 included in the environmental controller A42 in Figure 12(a) subtracts the output from the feedback block Fd from the sensing signal from the sound sensing device MA, which can be analogized to the subtraction operation performed by the signal processing circuit 72; the clean environment signal 722 can be analogized to the output of the subtractor A44.

[0055] Whether it is the feedback block Fd in Figure 12(a) or the difference estimation unit H2 in Figure 7, obtaining the information of the transfer function difference between the front and back channels is crucial, for example, F = Ff - Fb.

[0056] In short, the signal processing circuit of the present invention can obtain the difference in the transfer function corresponding to the front channel and the rear channel, and reduce the sound signal component corresponding to the sound emitted by the sound generating device, for example by subtracting / removing the difference estimate 723 (or similar to / equivalent to the output of the feedback block Fd in the environmental controller A42) from the sensing signal 721.

[0057] In addition, since the front and rear channels depend not only on the design of the shell, but also on the hairstyle, earrings, glasses worn that day, and the current wearing method of the earphones, there may be many variations, so recalibration is required to maintain optimal environmental control performance.

[0058] One embodiment may involve using a calibration test signal / tone (such as a series of logarithmic frequency scans with various durations and amplitudes) to optimize the (factory) curve of the difference response 631. This recalibration process can be initiated automatically each time the device is detected to be "worn in the ear" (e.g., via a proximity sensor) or manually initiated via user instruction (via touch, voice, or app control).

[0059] In other words, for recalibration, the signal processing circuitry (e.g., via a controller) can obtain the difference transfer function. Furthermore, the wearable device may optionally include a sensor (e.g., sensor 74 within wearable device 70) to detect whether the wearable device (e.g., 70) is being worn by a user. In one embodiment, sensor 74 may be a proximity sensor.

[0060] Please refer back to the dual-microphone configuration. Instead of removing residuals, it performs equalization on the sensing signal to reduce the sound signal component in the sensing signal and generate a clean ambient signal.

[0061] For example, Figure 13 illustrates a schematic diagram of a wearable device B1 according to an embodiment of the present invention, including a signal processing circuit B0. The signal processing circuit B0 is coupled to an ambient / first microphone B07a and a voice / second microphone B07v to receive first and second sensing signals from microphones B07a and B07v. The signal processing circuit B0 includes a block B22, mathematically represented as kv. The block B22 can be designed to satisfy Amic + kv∙Vmic = 0 or minimize ||Amic + kv∙Vmic|| as much as possible, where ||∙|| can represent or correspond to the energy or norm of the input parameters. In interpretation, Amic and Vmic can be interpreted as the sensing signals sensed by the ambient microphone and the voice microphone, respectively. In another interpretation, Amic and Vmic can represent the transfer functions from the sound generating device to the ambient microphone and to the voice microphone, respectively.

[0062] In one embodiment, kv can be obtained as kv = -Vmic / Amic (Equation 5) (where the forward slash " / " indicates "division by"), and the transfer function Vmic / Amic can be obtained using simulation software such as MATLAB with a "system identification" tool (where the forward slash " / " indicates "or"). In one embodiment, kv can be optimized over the frequency band of interest, for example, 20 to 8 kHz, but is not limited thereto.

[0063] It is worth noting that in the embodiment of Figure 13, block B22 or kv is used for Vmic. Block B22 or kv can also be used for Amic, and is not limited thereto.

[0064] In one embodiment, the signal processing circuit B0 can perform a subtraction operation (such as performing Vmic – Amic) on the sensed signal to obtain a speech signal. The reason for capturing speech through subtraction may be: 1) Ambient sound AS is usually in the far field and often produces almost the same output from B07a and B07b. Therefore, these signals often cancel each other out through subtraction; 2) The speech VC emitted by the user is in the near field and its intensity is ∝1 / r. Assuming that B07v is closer to the user's mouth and points towards the user's mouth, while B07a is farther from the user's mouth and points away from the user's mouth, this sound pressure level ∝1 / r will cause B07v to produce a higher output in response to VC than B07a. After subtraction, the significant part corresponding to the speech VC will remain.

[0065] Refer back to Equation 5 or block B22 with transfer function kv. It is beneficial to obtain the transfer function ratio between transfer function Vmic and transfer function Amic, and the equalization operation can be performed according to this ratio Vmic / Amic.

[0066] In other words, in a dual-microphone configuration, the signal processing circuit of the present invention can obtain a transfer function ratio, such as Vmic / Amic, and perform equalization operation on the sensing signal according to the transfer function ratio (such as through block B22 with transfer function kv), and combine the equalized signal (such as the output of block B22) with other sensing signals to reduce the sound signal components.

[0067] In one embodiment, block B22, the environment controller (including feedforward block HC and feedback block Fd), the difference estimate H2, and the anti-environment block H1 can be implemented through a digital infinite impulse response (IIR) filter, but are not limited thereto.

[0068] The above discussion also applies to environmental control of smart glasses, which suffer from the same problem of microphone isolation in sound generating devices. In addition to clear optical functions, the smart glasses of this application also have other functions. For example, smart glasses can be embedded with electronic devices to perform audio / video related operations.

[0069] For example, Figure 14 illustrates a schematic diagram of a wearable device C0 according to an embodiment of the present invention. The wearable device C0 may include a sound generating device C02, endpoints C03 and C06, and microphones C07a and C07v. In the embodiment of Figure 14, endpoint C03 may serve as a front end and is typically located at the position closest to the ear canal opening; endpoint C06 may serve as a rear end and is located near the hinge / bracket of the leg to maximize the low-frequency (e.g., less than 100Hz) frequency response; microphone C07v (for capturing the user's voice) may be located at a distance of ¼ of the distance from the rear end C06 to the front end C03; microphone C07a (for capturing sounds of the user's surrounding environment) may be located above endpoint C03 and / or near the end of the straight leg, but is not limited thereto.

[0070] In one embodiment, microphones C07a and C07v may be disposed at the node position.

[0071] In one embodiment, the wearable device C0 may include the above-described signal processing circuitry to reduce the sound signal component corresponding to the sound emitted by the sound generating device from the sensing signal sensed by the microphone.

[0072] In short, the present invention is used to establish isolation between a sound generating device and a sound sensing device, or between a sound generating device and an environmental sensing microphone, and provides an acoustic method for placing the microphone at a node position, and an electrical method for reducing sound signal components from the sensing signal, thereby generating a clean environmental signal that does not contain components corresponding to the sound emitted by the sound generating device. The above description is only a preferred embodiment of the present invention, and all equivalent variations and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention. [Simplified Explanation of the Diagram]

[0017] Figure 1 is a schematic diagram of a wearable device according to Embodiment 1 of this application. Figure 2 is a schematic diagram of a wearable device according to Embodiment 1 of this application. Figure 3 illustrates the sound energy distribution of forward and backward radiating waves in the space surrounding the wearable device shown in Figure 2. Figure 4 is a schematic diagram of a wearable device according to Embodiment 1 of this application. Figure 5 is a schematic diagram of a wearable device according to Embodiment 1 of this application. Figure 6 illustrates the amplitude response curves corresponding to forward and backward radiating waves and the differences between forward and backward radiating waves in the form of sound pressure level versus frequency. Figure 7 is a schematic diagram of a signal processing circuit according to Embodiment 1 of this invention. Figure 8 is a schematic diagram of a signal processing chain according to Embodiment 1 of this invention. Figure 9 is a schematic diagram of a signal processing circuit according to Embodiment 1 of this invention. Figure 10 is a schematic diagram of a wearable device according to Embodiment 1 of this application. Figure 11 is a schematic diagram of a system according to Embodiment 1 of this invention. Figure 12 is a schematic diagram of a system according to Embodiment 1 of this invention. Figure 13 is a schematic diagram of a wearable device according to Embodiment 1 of this application including a signal processing circuit. Figure 14 is a schematic diagram of a wearable device according to Embodiment 1 of this application.

Claims

1. A wearable device, comprising: a sound generating device, a first sound sensing device, and a second sound sensing device; wherein, The sound generating device generates a forward radiating wave and a backward radiating wave when emitting sound; wherein, the first sound sensing device is disposed at a first node position corresponding to one of the sound generating devices, and the second sound sensing device is disposed at a second node position corresponding to one of the sound generating devices; wherein, at the first node position and the second node position, the forward radiating wave and the backward radiating wave cancel each other out.

2. The wearable device as described in claim 1, comprising: a first end and a second end; wherein, The forward-radiated wave propagates outward through the first end, and the backward-radiated wave propagates outward through the second end.

3. The wearable device as described in claim 1, wherein, A first frequency response corresponding to the forward-radiated wave received on the first or second sound sensing device matches a second frequency response corresponding to the backward-radiated wave received on the first or second sound sensing device.

4. The wearable device as described in claim 1, wherein, The first sound sensing device is configured to receive a voice from a user; wherein the second sound sensing device is configured to receive an ambient sound from the surrounding environment.

5. The wearable device as described in claim 1, wherein, When a user wears the wearable device, the device emits sound into an open space.

6. The wearable device as described in claim 1, wherein, The wearable device is either an earphone or a pair of smart glasses.

7. The wearable device as described in claim 1, wherein, The sound generating device includes an air pulse generating device; wherein, the sound generating device emits sound by generating a plurality of air pulses at an ultrasonic pulse rate.

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