An active noise-cancelling audio device

Abstract

The embodiment of the present specification discloses an active noise reduction audio device. The device comprises a speaker, a microphone, an analog filter and a processing circuit. The speaker is used to generate noise reduction sound, the microphone is used to collect environmental noise and noise reduction sound, and generate a first analog signal. The analog filter is used to provide gain for the first analog signal and generate a second analog signal, wherein the second analog signal drives the speaker to generate noise reduction sound. The processing circuit is used to send control instructions to the analog filter according to the first analog signal and the second analog signal, so as to adjust the gain and phase shift of the analog filter. The present specification can reduce the time delay caused by the signal transformation link and the digital filter processing by using the analog filter to adjust the amplitude and phase of the analog signal and generating the noise reduction sound, so that the audio device can timely respond to the noise reduction, thereby improving the noise reduction effect.

Description

Technical Field

[0001] This manual relates to the field of audio noise reduction, and in particular to an active noise reduction audio device. Background Technology

[0002] Audio devices often employ active noise cancellation technology to reduce ambient noise. For example, audio devices can use microphones to collect and analyze external ambient noise, generating noise-canceling sounds that are out of phase with the ambient noise. Thus, when the sound emitted by the audio device enters the ear, the ambient noise and the noise-canceling sounds cancel each other out, achieving the effect of noise elimination.

[0003] Digital filter banks are typically used in audio equipment to adjust the gain and phase of audio signals. However, digital filter banks often generate significant time delays when processing signals, which can lead to an inability to process external environmental noise in a timely manner, resulting in a slow noise reduction response and affecting the noise reduction effect of audio equipment.

[0004] Therefore, it is necessary to propose an active noise cancellation device that can respond quickly. Summary of the Invention

[0005] One embodiment of this specification provides an active noise cancellation frequency device. The device includes a loudspeaker, a microphone, an analog filter, and processing circuitry. The loudspeaker generates noise-canceling sound, and the microphone collects ambient noise and the noise-canceling sound, generating a first analog signal. The analog filter provides gain to the first analog signal and generates a second analog signal, wherein the second analog signal drives the loudspeaker to generate the noise-canceling sound. The processing circuitry sends control commands to the analog filter based on the first and second analog signals to adjust the gain and phase shift of the analog filter.

[0006] The embodiments in this specification use analog filters to adjust the amplitude and phase of analog signals and thereby generate noise-reduced audio. This reduces the time delay caused by signal transformation (such as digital-to-analog conversion) and digital filter processing, allowing audio devices to respond to noise reduction in a timely manner, thus improving the noise reduction effect.

[0007] Furthermore, the active noise cancellation frequency device provided in the embodiments of this specification can also be equipped with a processing circuit. The processing circuit adjusts the gain and phase shift of the analog filter according to the ambient noise and the analog signal corresponding to the noise cancellation sound, so that the analog filter can achieve the optimal response to the ambient noise and further improve the noise cancellation effect.

[0008] In some embodiments, the processing circuit adjusts the gain and phase shift of the analog filter, including: within a specific time range, the processing circuit controls the analog filter to dynamically adjust its gain as the amplitude of the first analog signal changes.

[0009] In some optional embodiments, the processing circuitry includes a first analog-to-digital converter (ADC) and a second ADC. The first ADC samples a first analog signal to generate a first digital signal, and the second ADC samples a second analog signal to generate a second digital signal. The processing circuitry sends control commands to the analog filter, including sending control commands to the analog filter based on the first and second digital signals.

[0010] In some embodiments, the analog filter includes a switching gating circuit and a response regulator. The switching gating circuit adjusts the resistance or capacitance value of the response regulator according to a control command to change the amplitude frequency response and phase frequency response of the analog filter.

[0011] In some embodiments, the response regulator includes one or more phase modulation units, each phase modulation unit including at least one adjustable resistor or at least one adjustable capacitor. The switching gating circuit adjusts the resistance or capacitance value of the response regulator according to a control command, including: the switching gating circuit adjusting the resistance value of the adjustable resistor or the capacitance value of the adjustable capacitor according to the control command.

[0012] In some optional embodiments, the active noise cancellation device further includes a first analog adder, a first analog-to-digital converter (ADC), and a third ADC. The first analog adder generates a third analog signal based on a first analog signal, a second analog signal, and a secondary response corresponding to the second analog signal, where the secondary response is a speaker-to-microphone response. The first ADC samples the first analog signal to generate a first digital signal, and the third ADC samples the third analog signal to generate a third digital signal. A processing circuit sends control commands to the analog filter, including sending control commands to the analog filter based on the first and third digital signals.

[0013] In some embodiments, the active noise cancellation audio device further includes a fixing structure that fixes the speaker and microphone in positions near the user's ear without blocking the user's ear canal.

[0014] In some optional embodiments, the active noise cancellation device further includes a first analog adder, a third analog-to-digital converter (ADC), and a fourth ADC. The first analog adder generates a third analog signal based on a first analog signal, a second analog signal, and a secondary response corresponding to the second analog signal, where the secondary response is the speaker-to-microphone response. The third ADC samples the third analog signal to generate a third digital signal, and the fourth ADC samples the second analog signal with the added secondary response to generate a fourth digital signal. A processing circuit sends control commands to the analog filter, including: determining a fifth digital signal based on the third digital signal and a transfer function between the user's ear canal and the microphone, and sending control commands to the analog filter based on the fourth and fifth digital signals.

[0015] In some embodiments, the transfer function between the user's ear canal and the microphone is obtained through experimental testing, or based on a statistical model or a neural network model.

[0016] In some embodiments, the processing circuitry periodically sends control commands to the analog filter. Attached Figure Description

[0017] This specification will be further described by way of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting; in these embodiments, the same reference numerals denote the same structures, wherein:

[0018] Figure 1 This is a structural block diagram of an active noise cancellation frequency device according to some embodiments of this specification;

[0019] Figure 2 This is a simplified structural diagram of an active noise cancellation frequency device according to some embodiments of this specification;

[0020] Figure 3A This is a schematic diagram of the phase modulation unit according to some embodiments of this specification;

[0021] Figure 3B This is a schematic diagram of the phase modulation unit according to some embodiments of this specification;

[0022] Figure 4 This is a schematic diagram of the structure of an active noise cancellation frequency device according to some embodiments of this specification;

[0023] Figure 5 This is a schematic diagram of the structure of an active noise cancellation frequency device according to some embodiments of this specification;

[0024] Figure 6 This is a structural schematic diagram of an active noise cancellation frequency device according to some embodiments of this specification. Detailed Implementation

[0025] To more clearly illustrate the technical solutions of the embodiments in this specification, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of this specification. For those skilled in the art, these drawings can be applied to other similar scenarios without creative effort. Unless obvious from the context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0026] It should be understood that the terms “system,” “device,” “unit,” and / or “module” used herein are one way to distinguish different components, elements, parts, sections, or assemblies at different levels. However, if other terms can achieve the same purpose, they may be replaced by other expressions.

[0027] As indicated in this specification and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of expressly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0028] Flowcharts are used in this specification to illustrate the operations performed by the system according to embodiments of this specification. It should be understood that the preceding or following operations are not necessarily performed in exact order. Instead, the steps can be processed in reverse order or simultaneously. Furthermore, other operations can be added to these processes, or one or more steps can be removed from them.

[0029] The active noise cancellation (ADC) audio devices of one or more embodiments in this specification can provide noise-canceling audio based on ambient noise, so as to be applied in various scenarios where environmental noise interference needs to be avoided. For example, they can provide noise-canceling audio to audio output devices (such as speakers, headphones, etc.) to improve the quality of audio output; or they can provide noise-canceling audio to audio input devices (such as pickups, microphones, etc.) to improve the quality of audio acquisition. In some embodiments, the active noise cancellation audio device can adjust the output noise-canceling audio level in real time according to the level of ambient noise, so that the active noise cancellation audio device can respond optimally to ambient noise and improve the noise reduction effect.

[0030] In some embodiments, the active noise cancellation (ADC) device can be a feedback active noise cancellation device or a feedforward active noise cancellation device. In a feedforward active noise cancellation device, the microphone primarily receives ambient noise, which is then converted into corresponding noise-canceling sounds by a speaker. In a feedback active noise cancellation device, the microphone can simultaneously collect both ambient noise and the noise-canceling sounds generated by the speaker. The processing circuit then generates a feedback signal to drive the speaker to adjust the noise-canceling sounds based on the combined effect of the ambient noise and the noise-canceling sounds, thereby achieving the noise reduction effect. In some embodiments, the active noise cancellation device can also employ other noise reduction methods, such as a combination of feedforward and feedback active noise cancellation.

[0031] Currently, active noise cancellation (ADC) audio devices can include digital filter banks, analog-to-digital converters (ADCs), and digital-to-analog converters (DACs). The ADC converts sound received by the microphone (ambient noise, or a combination of ambient noise and noise-canceling sound) into a digital signal. The digital filter bank processes this digital signal to generate a corresponding noise-canceling digital signal, which is then converted back to an analog signal by the DAC and output through a speaker to cancel out ambient noise. However, using digital filter banks for signal processing introduces significant time delays, which can cause active noise cancellation devices to fail to process ambient noise in a timely manner, resulting in a slow noise cancellation response and affecting the real-time noise reduction performance of the audio equipment.

[0032] The active noise cancellation audio device provided in the embodiments of this specification uses an analog filter to directly process the analog signal corresponding to the noise-canceling audio (e.g., gain or phase shift), which can reduce the signal transformation (e.g., digital-to-analog conversion) stage and the time delay caused by digital filter processing, so that the audio device can perform noise reduction processing in a timely manner, thereby improving the noise reduction effect.

[0033] Furthermore, the active noise cancellation frequency device provided in the embodiments of this specification can also be equipped with a processing circuit. The processing circuit adjusts the gain and phase shift of the analog filter according to the ambient noise and the analog signal corresponding to the noise cancellation sound, so that the analog filter can achieve the optimal response to the ambient noise and further improve the noise cancellation effect.

[0034] Figure 1 This is a structural block diagram of an active noise cancellation frequency device according to some embodiments of this specification. In some embodiments, such as Figure 1 As shown, the active noise cancellation frequency device 100 may include: a speaker 110, a microphone 120, an analog filter 130, and a processing circuit 140.

[0035] The speaker 110 is a transducer that converts electrical signals into sound signals. In some embodiments, the active noise-canceling audio device 100 is an open-back headphone, and the speaker 110 can be located near the user's ear without obstructing it. For example, the support structure of the open-back headphone can fix the speaker (or the housing housing the speaker) to the periphery of the user's auricle (e.g., the front of the tragus) or inside the auricle contour (e.g., near the triangular fossa) by suspension or clamping. In some embodiments, the active noise-canceling audio device 100 is a closed-back headphone (e.g., in-ear headphones or over-ear headphones), and the support structure of the closed-back headphone can place the speaker 110 inside the user's ear canal or within a closed space formed by the housing structure surrounding the user's ear. In some embodiments, the support structure can be a fastener such as an ear hook or a headband. For example, the active noise cancellation audio device 100 can be an external speaker, a speaker, a bone conduction headphone, an air conduction headphone, an AR device, a VR device, a head-mounted audio device, an in-vehicle audio device, a hearing aid, etc. Alternatively, the active noise cancellation audio device 100 can be part of an in-vehicle audio system or an indoor audio system to actively cancel noise at specific locations in a space.

[0036] In some embodiments, the speaker 110 may output a noise-canceling tone that has an opposite phase to the ambient noise, so that the noise-canceling tone can cancel out the ambient noise. Further, the phase difference between the noise-canceling tone and the ambient noise at the user's ear canal may be 180 degrees. In some embodiments, the speaker 110 may also output other audio, such as alert sounds, audio played according to user needs, etc.

[0037] Microphone 120 is a transducer that converts sound signals into electrical signals. In some embodiments, microphone 120 can simultaneously collect ambient noise and noise-canceling sound, and transmit the collected sound to analog filter 130 or processing circuit 140 for processing, providing feedback on the magnitude and phase of the noise-canceling sound to minimize the sound collected by microphone 120. In this case, the microphone can be called a feedback microphone. The feedback microphone can be positioned close to the user's ear canal to make the received sound as close as possible to the sound actually received by the user's ear. In some embodiments, microphone 120 can be primarily used to collect ambient noise, collecting as little noise-canceling sound as possible from speaker 110. In this case, the microphone can be called a feedforward microphone. To reduce the influence of speaker 110 on the feedforward microphone, a physical structure to isolate sound transmission can be provided between the feedforward microphone and speaker 110, or the feedforward microphone can be positioned away from speaker 110, or the feedforward microphone can be located near the acoustic null point of speaker 110.

[0038] In some embodiments, when the microphone is a feedback microphone, ambient noise and noise-reduced sound can be collected simultaneously, and a first analog signal corresponding to the ambient noise and noise-reduced sound can be generated. The amplitude of the first analog signal can reflect the degree to which the ambient noise and noise-reduced sound cancel each other out. To achieve the desired noise reduction effect, the amplitude of the first analog signal should be as small as possible, even reduced to 0.

[0039] It should be noted that, compared to closed or semi-closed audio devices, the microphone in an open audio device is not located at the user's ear canal, resulting in a discrepancy between the sound received by the user's ear canal and the sound received by the microphone. In some embodiments, a transfer function can be constructed between the user's ear canal and the microphone to represent the correspondence between the sound signal received by the user's ear canal and the sound signal received by the microphone. For specific implementations of open audio devices, please refer to the following... Figure 6 The relevant content will not be repeated here.

[0040] To better describe the relationship between speaker 110 and microphone 120 Figure 2 Describe the specific implementation of the speaker and microphone using examples.

[0041] Figure 2 This is a simplified structural diagram of an active noise cancellation frequency device according to some embodiments of this specification.

[0042] like Figure 2 As shown, y(t) represents the analog signal received by the speaker 110 corresponding to the noise-reduced sound, also known as the second analog signal, which the speaker 110 can use to generate the noise-reduced sound; p(t) represents the analog signal corresponding to the ambient noise received by the microphone 120; e(t) is the first analog signal generated by the microphone 120 based on the simultaneously received ambient noise and noise-reduced sound. Therefore, the relationship between the above three signals can be expressed as:

[0043] e(t) = p(t) + y(t). (1)

[0044] In some embodiments, in order to make the generated noise-reduced sound cancel out the ambient noise, the first analog signal e(t) is processed (such as phase shifting by a phase shifter and amplification by an amplifier) ​​to generate a second analog signal y(t). Ideally, the second analog signal y(t) and the analog signal p(t) corresponding to the ambient noise will cancel each other out, thereby reducing the amplitude of the first analog signal e(t) to 0. It should be noted that the description of the processing of the first analog signal e(t) here is for illustrative purposes only and does not limit the corresponding modifications that can be made by those skilled in the art based on their understanding of the principle. For example, the first analog signal e(t) can be phase-shifted or amplified by different electronic devices such as amplifiers and phase shifters, or the same electronic device (e.g., an analog filter) can simultaneously perform phase shifting and amplification of the first analog signal e(t).

[0045] Analog filter 130 is a circuit device for filtering analog or continuous-time signals. In some embodiments, analog filter 130 can perform signal processing on analog signals. For example, analog filter 130 can simultaneously phase-shift and amplify analog signals to adjust the phase and amplitude of the analog signals.

[0046] In some embodiments, the analog filter 130 can be used to provide gain to the first analog signal and generate a second analog signal, which drives the speaker 110 to produce noise-reduced sound. Referring, for example, further reference is made to the above description. Figure 2 The gain of analog filter 130 can be expressed as h(t) in the time domain and H(s) in the frequency domain. Analog filter 130 can provide a gain h(t) for the first analog signal e(t) and generate the second analog signal y(t). Therefore, the relationship between the above three signals can be expressed in the time domain as follows:

[0047] y(t)=e(t)*h(t), (2)

[0048] Where * represents the convolution operation. In some embodiments, according to the above formulas (1) and (2), the correspondence between the first analog signal e(t) and the gain h(t) of the analog filter 130 in the time domain and frequency domain, respectively, can be expressed as:

[0049]

[0050] Where E(s) is the frequency domain representation of the first analog signal, P(s) is the frequency domain representation of the analog signal corresponding to the environmental noise, and H(S) is the frequency domain gain of the analog filter 130.

[0051] As shown in formula (3), the larger the gain H(S) of the analog filter 130, the closer the value of the first analog signal E(s) is to 0, and the closer it is to the ideal state of active noise reduction (i.e., the second analog signal y(t) and the analog signal p(t) corresponding to the ambient noise can cancel each other out). Therefore, the active noise reduction frequency device 100 can be equipped with an analog filter 130 with a large gain H(S) to improve the noise reduction effect.

[0052] In some embodiments, the analog filter 130 can adjust its gain and phase shift according to control commands from the processing circuit 140 to avoid unstable noise reduction performance of the active noise-canceling frequency device 100 due to excessive or insufficient gain. For example, when the active noise-canceling frequency device 100 is in its initial state, the value of the first analog signal mainly comes from the contribution of ambient noise (i.e., the second analog signal in the initial state is small or approximately zero). At this time, the analog filter 130 can be set to have a small gain to prevent the first analog signal from being over-amplified and generating a second analog signal with excessive amplitude in the next moment, which could cause the speaker to emit excessive noise and damage the device. Within a specific time range, as the amplitude of the first analog signal changes, the processing circuit 140 can control the analog filter 130 to dynamically adjust its gain. For example, for a period of time after the active noise-canceling frequency device 100 is in its initial state, as the amplitude of the first analog signal decreases, the gain of the analog filter 130 can be continuously increased, thereby preventing the second analog signal from being unable to cancel out the analog signal corresponding to the ambient noise due to insufficient gain. The specific adjustment method of the analog filter 130 can be referred to the relevant content of the processing circuit below, and will not be repeated here. In some embodiments, during the operation of the active noise cancellation frequency device 100, when ambient noise fluctuates, the analog filter 130 can also dynamically adjust its gain under the control of the processing circuit 140 to adapt to changes in ambient noise. For example, at a certain moment, when the ambient noise increases, the amplitude of the first analog signal will increase accordingly. The processing circuit 140 can control the analog filter 130 to reduce its gain to prevent the first analog signal from being over-amplified and causing damage to the speaker.

[0053] In some embodiments, the analog filter 130 may include a switching gating circuit and a response regulator. The switching gating circuit adjusts the resistance or capacitance value of the response regulator according to a control command to change the amplitude frequency response and phase frequency response of the analog filter 130, thereby realizing phase shifting and / or amplification processing of the first analog signal.

[0054] In some embodiments, the switch-gated circuit can adjust the resistance or capacitance value of the response regulator using an analog switch. Furthermore, different channels of the response regulator correspond to different resistance or capacitance values, and the analog switch can change the channel of the response regulator by changing its position, thereby adjusting the resistance or capacitance value of the response regulator. For example, the response regulator includes a potentiometer, and changing the position of the analog switch changes the channel through which the potentiometer is connected to the circuit, thus changing the resistance value of the response regulator.

[0055] In some embodiments, the switch gating circuit can adjust the state of the switch itself according to a control command. For example, when the control command is a pulse signal, the switch gating circuit can adjust the position of the analog switch according to the frequency of the pulse signal. In some embodiments, the switch gating circuit can periodically receive control signals from the processing circuit 140. Specific implementation details of the control signals can be found in the relevant description of the processing circuit below, and will not be repeated here.

[0056] A response regulator can be a circuit device for processing signals. For example, the response regulator can perform signal processing (e.g., phase shifting and amplification) on an input first analog signal to obtain a second analog signal. In some embodiments, the resistance or capacitance value of the response regulator can affect the amplitude-frequency response and phase-frequency response of the analog filter 130, thereby affecting the signal processing effect. For example, if the first analog signal remains unchanged, but the resistance or capacitance value of the response regulator changes, the amplitude-frequency response and phase-frequency response of the analog filter 130 will change, causing the amplitude and phase of the second analog signal output by the analog filter 130 to change accordingly. The specific implementation of the response regulator will be described in detail below using a phase modulation unit as an example.

[0057] In some embodiments, the response regulator may include one or more phase modulation units, each phase modulation unit may include at least one adjustable resistor or at least one adjustable capacitor. Correspondingly, the switch gating circuit may adjust the resistance value of the adjustable resistor or the capacitance value of the adjustable capacitor according to a control command.

[0058] The phase modulation unit can be a circuit assembly of multiple adjustable parameters. In some embodiments, the response regulator can change the resistance or capacitance value of the response regulator by changing the resistance value of the adjustable resistor or the capacitance value of the adjustable capacitor in the phase modulation unit. The adjustable resistor can be a sliding rheostat, potentiometer, resistor, etc., and the specific type of the adjustable resistor can be selected according to the type of switch gating circuit. The adjustable capacitor can be a surface-mount adjustable capacitor, through-hole adjustable capacitor, etc., and the specific type of the adjustable capacitor can be selected according to the type of switch gating circuit. Figure 3A and Figure 3B The specific implementation of the phase modulation unit is described with examples.

[0059] Figure 3A This is a schematic diagram of the phase modulation unit according to some embodiments of this specification.

[0060] like Figure 3A As shown, the phase modulation unit 310 may include a capacitor C1, a resistor R1, and a voltage follower Q1. The capacitor C1 and resistor R1 are connected in series, with one end of the capacitor C1 grounded. The connection point of the capacitor C1 and resistor R1 is connected to the non-inverting input terminal of the voltage follower Q1, and the inverting input terminal of the voltage follower Q1 is connected to its output terminal. The phase modulation unit 310 can process the signal Ui1 to obtain the signal Uo1. In this embodiment, the voltage follower Q1 can prevent the phase modulation unit 310 from being affected by subsequent circuits, maintaining the stable operation of the phase modulation unit 310.

[0061] Figure 3B This is a schematic diagram of the phase modulation unit according to some embodiments of this specification.

[0062] like Figure 3B As shown, multiple phase modulation units 320 are connected in series. Each phase modulation unit 320 may include a capacitor (e.g., capacitor C2) and a resistor (e.g., resistor R2) connected in series. The resistor (e.g., capacitor C2) in this phase modulation unit 320 is connected in series with the resistors (e.g., resistors R3 and R4) of other phase modulation units 320, and the capacitor (e.g., capacitor C2) in this phase modulation unit 320 is connected in parallel with the capacitors (e.g., capacitors C3 and C4) of other phase modulation units 320. The multiple phase modulation units 320 can process the signal Ui2 to obtain the signal Uo2.

[0063] In some embodiments, the range of the phase frequency response of the response regulator can be adjusted by changing the number of the series-connected phase modulation units 320. For example, the more series-connected phase modulation units 320 there are, the larger the range of the phase frequency response of the response regulator.

[0064] Therefore, the transfer function of the phase modulation unit (such as the phase modulation unit 310 and phase modulation unit 320 mentioned above) can be expressed as:

[0065]

[0066] Where R is the resistance value of the phase modulation unit and C is the capacitance value of the phase modulation unit. Correspondingly, the phase frequency response of a phase modulation unit can be expressed as: -arctan(wRC), and the range of the phase frequency response can be [-90°, 0°].

[0067] In some embodiments, capacitors C1-C4 can be adjustable capacitors, or resistors R1-R4 can be adjustable resistors. It should be noted that... Figures 3A-3BOnly resistors R1-R4 are shown as adjustable resistors. Adjusting the capacitance (e.g., capacitors C1-C4) or the resistance (e.g., resistors R1-R4) of the adjustable capacitors can change the phase frequency response of the phase modulation unit within the range of [-90°, 0°]. Correspondingly, the switch gate circuit can adjust the path of the circuit according to the control command using the analog switch corresponding to the adjustable device, thereby adjusting the capacitance of capacitors C1-C4 or the resistance of resistors R1-R4.

[0068] In the embodiments of this specification, the amplitude frequency response and phase frequency response of the analog filter 130 can be adjusted by the cooperation of the switching gate circuit and the response regulator, so as to avoid the analog filter 130 providing too much or too little gain at a specific time, so as to achieve the optimal response of the analog filter 130 to environmental noise, thereby improving the noise reduction effect of the active noise cancellation device 100.

[0069] The processing circuit 140 can be a circuit unit with data processing and control functions. In some embodiments, the processing circuit 140 may include circuit modules such as integrated circuit ASIC, field programmable gate array (FPGA), complex programmable logic device (CPLD), microcontroller unit (MCU), central processing unit (CPU), digital signal processor (DSP), or graphics processing unit (GPU).

[0070] In some embodiments, within a specific time range, as the amplitude of the first analog signal changes, the processing circuit 140 can control the analog filter 130 to dynamically adjust its gain. For example, the specific time range can be the period after the active noise cancellation device 100 starts operating. As the active noise cancellation device 100 starts operating, the processing circuit 140 can send control commands as the amplitude of the first analog signal decreases, gradually increasing the gain of the analog filter 130, thereby keeping the amplitude of the second analog signal close to the analog signal corresponding to the ambient noise, and improving the noise reduction effect of the device.

[0071] It should be noted that when the active noise cancellation device 100 is in the initial state (i.e., the active noise cancellation device 100 starts working), since most of the external environmental noise is not canceled, the amplitude of the first analog signal is relatively large. At this time, the processing circuit 140 can issue a control command to control the analog filter 130 to have a smaller gain, so as to avoid the amplitude of the second analog signal being too large and ensure that the active noise cancellation device 100 can work stably in the initial state.

[0072] In some embodiments, the processing circuit 140 may send control commands to the analog filter 130 based on the first analog signal and the second analog signal to adjust the gain and phase shift of the analog filter 130.

[0073] The first analog signal can reflect the degree to which ambient noise and noise reduction cancel each other out, and the second analog signal can reflect the magnitude of the noise reduction. In some embodiments, the control command can be a high-level signal or a pulse signal, etc., and the specific type of control command can be selected according to the type of processing circuit 140.

[0074] In some embodiments, the processing circuit 140 can adjust the gain and phase shift of the analog filter 130 by adjusting the frequency of the control command. Figure 4 The specific implementation of the processing circuit 140 is explained in detail with examples.

[0075] Figure 4 This is a structural schematic diagram of an active noise cancellation frequency device 100 according to some embodiments of this specification.

[0076] like Figure 4 As shown, y(t) represents the second analog signal, and e(t) represents the first analog signal. The processing circuit 140 can calculate the required coefficients (such as gain and phase shift) of the analog filter 130 based on the first analog signal e(t) and the second analog signal y(t), and calculate the amplitude-frequency response and phase-frequency response of the analog filter 130. It then generates control commands corresponding to the amplitude-frequency response and phase-frequency response and sends them to the analog filter 130. The analog filter 130 can adjust its gain and phase shift according to the control commands to make its actual gain and phase shift close to the calculated gain and phase shift. For a detailed explanation of how to adjust the analog filter 130, please refer to the above description. Figures 3A-3B The relevant content will not be repeated here.

[0077] In the embodiments of this specification, the processing circuit 140 generates a control signal based on the analog signal corresponding to the ambient noise and the noise reduction sound, so as to adjust the gain and phase shift of the analog filter 130, so that the analog filter 130 achieves the optimal response to the ambient noise and further improves the noise reduction effect.

[0078] In some embodiments, the processing circuit 140 may include a first analog-to-digital converter (ADC) and a second ADC. The first ADC samples a first analog signal to generate a first digital signal, and the second ADC samples a second analog signal to generate a second digital signal. Correspondingly, the processing circuit 140 may send control commands to the analog filter 130 based on the first and second digital signals.

[0079] In some embodiments, an analog-to-digital converter (e.g., a first analog-to-digital converter, a second analog-to-digital converter) can sample analog signals (e.g., a first analog signal, a second analog signal) according to a preset sampling rate to generate discrete digital signals (e.g., a first digital signal, a second digital signal). Correspondingly, the processing circuit 140 can generate control signals based on the first digital signal and the second digital signal. For example, as shown... Figure 4 As shown, the first analog-to-digital converter 141 samples the first analog signal e(t) to generate the first digital signal e(n), and the second analog-to-digital converter 142 samples the second analog signal y(t) to generate the second digital signal y(n).

[0080] In some implementations, the processing circuit 140 can calculate the coefficients (such as gain and phase shift) of the analog filter 130 based on the first digital signal and the second digital signal, using noise reduction algorithms such as adaptive filtering algorithm (Least Mean Square, LMS) and filtered-x least mean square (FXLMS), thereby generating control commands corresponding to the coefficients.

[0081] In the embodiments of this specification, analog signals are converted into digital signals by an analog-to-digital converter, which is compatible with the analog filter 130 that performs signal processing in the analog domain and the processing circuit 140 that performs signal processing in the digital domain, thereby realizing analog-to-digital integration and expanding the application scenarios of the active noise cancellation device 100.

[0082] Since analog-to-digital conversion and signal processing require time, in some embodiments, the processing circuit 140 can periodically send control commands to the analog filter 130. Correspondingly, the switching gating circuit can adjust the resistance or capacitance value of the response regulator in each cycle to regulate the amplitude-frequency response and phase-frequency response of the analog filter 130.

[0083] In some embodiments, the processing circuit 140 may determine the period for sending control commands based on one or more delay-related factors, such as the sampling rate of the analog-to-digital converter 130, the signal conversion time, the update time of the switching gating circuit, and the signal processing time of the processing circuit 140. For example, when the sampling rate of the analog-to-digital converter is 16kHz, and the point-by-point update of the switching gating circuit takes approximately 0.06ms, the analog filter 130 takes 1ms to process the signal, and the analog-to-digital conversion and switching gating circuit delays require approximately 5ms of delay, the period for sending control commands may be determined to be 1s. The specific time parameters provided above are for illustrative purposes only and are not specifically limited in this specification.

[0084] In some embodiments, when the active noise cancellation device 100 is operating stably, the processing circuit 140 may stop sending control commands to the analog filter 130 to stop regulating the amplitude-frequency response and phase-frequency response of the analog filter 130. Furthermore, when the amplitude of the first analog signal is within a preset amplitude range, the processing circuit 140 may stop sending control commands to the analog filter 130. When the amplitude of the first analog signal is within the preset amplitude range, it indicates that the first analog signal is close to 0, meaning that the active noise cancellation device 100 is in an ideal state of active noise cancellation and is operating stably.

[0085] In some embodiments, such as Figure 4 As shown, the active noise cancellation device 100 may further include an amplifier 150, which can be combined with the analog filter 130 to amplify the first analog signal e(t). In some embodiments, the active noise cancellation device 100 may also omit the amplifier 150 and amplify the first analog signal e(t) solely through the analog filter 130.

[0086] In some embodiments, since the response of the secondary channel in the audio device affects the noise reduction effect, the active noise cancellation audio device 100 can compensate for the secondary response. The secondary response is the response of the secondary channel in the audio device, which can reflect the effect of the sound transmission path from the speaker to the microphone on the sound signal. Figure 5 The specific implementation of compensating for secondary responses is explained in detail with examples.

[0087] Figure 5 This is a structural schematic diagram of an active noise cancellation frequency device 100 according to some embodiments of this specification.

[0088] like Figure 5 As shown, y(t) represents the second analog signal. This represents the secondary response, i.e., the transfer function from the speaker to the microphone. This represents the secondary response signal, which can be understood as adding a secondary response. The second analog signal y(t) follows.

[0089] An analog adder is an electronic device that performs operations on multiple analog signals. In some embodiments, the analog adder can be an operational amplifier-based adder circuit, such as an inverting adder circuit or a non-inverting adder circuit. In some embodiments, a first analog adder can generate a third analog signal by performing an addition operation on a first analog signal and an inverted secondary response signal to compensate for the secondary response. The third analog signal can reflect the superimposed sound wave of ambient noise and noise reduction canceled out, and the inverted noise reduction sound wave after passing through the secondary channel, i.e., the ambient noise after secondary response compensation.

[0090] For example, continue to refer to the above. Figure 5 , This represents the analog signal corresponding to the environmental noise after secondary response compensation, i.e., the third analog signal output by analog adder 160. In some embodiments, the relationship between the secondary response, the first analog signal, the second analog signal, and the third analog signal can be expressed as:

[0091]

[0092] in, The third analog signal, This is the secondary response signal, which is the response added from the speaker to the microphone. The second analog signal is y(t), and e(t) is the first analog signal.

[0093] Correspondingly, in some embodiments, a first analog-to-digital converter samples a first analog signal to generate a first digital signal, and a third analog-to-digital converter samples a third analog signal to generate a third digital signal. The processing circuit 140 can send control commands to the analog filter 130 based on the first and third digital signals to adjust the amplitude-frequency response and phase-frequency response of the analog filter 130 while compensating for the secondary response.

[0094] For example, continue to refer to the above. Figure 5 The first analog-to-digital converter 141 samples the first analog signal e(t) to generate the first digital signal e(n), and the third analog-to-digital converter 143 samples the third analog signal... Sampling to generate a third digital signal Processing circuit 140 can process the first digital signal e(n) and the third digital signal. Determine the coefficients of analog filter 130. In compensating for the secondary response, the updated coefficients of analog filter 130 can be expressed as:

[0095]

[0096] Where w(n+1) represents the coefficients that need to be updated in analog filter 130, and w(n) represents the coefficients that were last updated in analog filter 130. e(n) is the third digital signal, and e(n) is the first digital signal. The adjustment value of analog filter 130 can be obtained by processing the first and third digital signals using a noise reduction algorithm (such as LMS algorithm or FXLMS algorithm).

[0097] In some embodiments, after determining the coefficients of the analog filter 130 in the case of compensating for the secondary response, the processing circuit 140 sends a control command to the analog filter 130 to make the actual gain and phase shift of the analog filter 130 close to the calculated updated coefficients, so that the analog filter 130 can approach the optimal response to environmental noise. For a specific implementation of adjusting the analog filter 130, please refer to the above description. Figures 3A-3B The relevant content will not be repeated here.

[0098] In the embodiments of this specification, by using an analog adder to compensate for the secondary response, signal compensation can be achieved in the analog domain, avoiding the time delay caused by processing signals in the digital domain. This ensures that the analog filter 130 can process external environmental noise in a timely manner, while improving the accuracy of noise reduction and further enhancing the noise reduction effect of the active noise cancellation frequency device 100.

[0099] In some embodiments, when the active noise cancellation audio device 100 is an open audio device (i.e., the speaker is close to but does not block the ear), the response of the channel between the user's ear canal and the microphone will affect the noise cancellation effect. Therefore, the active noise cancellation audio device 100 can construct the transfer function between the user's ear canal and the microphone to compensate for this, i.e., perform open response compensation.

[0100] The transfer function between the user's ear canal and the microphone can represent the impact on sound transmission between the user's ear canal and the microphone. In some embodiments, the transfer function between the user's ear canal and the microphone can be obtained through experimental testing, or based on statistical models or neural network models.

[0101] For example, the response H1 between the speaker and the microphone, and the response H2 between the speaker and the user's ear canal can be obtained through testing (such as artificial head testing), and then the relationship between the responses H1 and H2 can be used to determine the response. Obtain the transfer function between the user's ear canal and the microphone. Alternatively, based on the response H1 between the speaker and microphone, a statistical model (such as a Gaussian mixture model) or a neural network model can be run to obtain the transfer function of the model output.

[0102] In some embodiments, the active noise cancellation device 100 may further include a first analog adder, a third analog-to-digital converter (ADC), and a fourth ADC. The fourth ADC can sample the secondary response signal to generate a fourth digital signal for signal processing by the processing circuit 140. Specific implementations of the analog adder and ADC can be found above. Figures 4-5 The relevant descriptions in the text will not be repeated here. The processing circuit 140 can determine the fifth digital signal based on the third digital signal and the transfer function between the user's ear canal and the microphone, and send control commands to the analog filter 130 based on the fourth and fifth digital signals to adjust the amplitude-frequency response and phase-frequency response of the analog filter 130 while compensating for secondary and open responses. Further, in some embodiments, the processing circuit 140 can perform an addition operation on the fourth and fifth digital signals to obtain a sixth digital signal, and send control commands to the analog filter 130 based on the third and sixth digital signals.

[0103] The third digital signal reflects the environmental noise after secondary response compensation. The fourth digital signal reflects the noise-reduced sound after adding a secondary response. The fifth digital signal reflects the sound wave obtained after secondary response compensation of the noise-reduced sound under the influence of open response. The sixth digital signal reflects the sound wave obtained after secondary response compensation and open response compensation of the noise-reduced sound. Figure 6 The specific implementation of open response compensation is explained in detail with examples.

[0104] Figure 6 This is a structural schematic diagram of an active noise cancellation frequency device 100 according to some embodiments of this specification.

[0105] like Figure 6 As shown, The fourth analog-to-digital converter 144 represents the transfer function between the user's ear canal and the microphone, and can process the secondary response signal. Sampling to generate a fourth digital signal This represents the fifth digital signal under the influence of open response. This represents the sixth digital signal after secondary response compensation and open response compensation. Therefore, based on the transfer function between the user's ear canal and the microphone, the relationship between the fifth, fourth, and third digital signals can be expressed as:

[0106]

[0107] in, The sixth digital signal, The fifth digital signal, It is the fourth digital signal, and * indicates a convolution operation. This is the transfer function corresponding to the secondary response. In other words, the processing circuit 140 can process the fourth digital signal. and the fifth digital signal Perform addition to obtain the sixth digital signal. The processing circuit 140 can also determine the coefficients of the analog filter 130 based on the third and sixth digital signals. In compensating for the secondary response and open response, the updated coefficients of the analog filter 130 can be expressed as:

[0108]

[0109] Where w′(n+1) represents the coefficients that need to be updated in the current iteration of analog filter 130, and w′(n) represents the coefficients that were last updated in analog filter 130. It is the third digital signal. The sixth digital signal, The adjustment value of analog filter 130 can be obtained by processing the third and sixth digital signals using a noise reduction algorithm (such as LMS algorithm or FXLMS algorithm).

[0110] In some embodiments, after determining the coefficients of the analog filter 130 in the case of compensating for the secondary response and open response, the processing circuit 140 sends a control command to the analog filter 130 to make the actual gain and phase shift of the analog filter 130 close to the calculated updated coefficients, so that the analog filter 130 can approach the optimal response to ambient noise. For specific implementation methods of adjusting the analog filter 130, please refer to the above description. Figures 3A-3B The relevant content will not be repeated here.

[0111] In the embodiments of this specification, when the active noise cancellation frequency device 100 is an open audio device, compensating for the transfer function between the user's ear canal and the microphone can improve the accuracy of noise cancellation and further enhance the noise cancellation effect of the active noise cancellation frequency device 100.

[0112] The beneficial effects that the embodiments of this specification may bring include, but are not limited to: (1) Using an analog filter to directly process the analog signal corresponding to the noise-reducing sound (e.g., gain or phase shift) can reduce the signal transformation (e.g., digital-to-analog conversion) stage and the time delay caused by digital filter processing, so that the audio device can respond to noise reduction in a timely manner, thereby improving the noise reduction effect. (2) The processing circuit adjusts the gain and phase shift of the analog filter according to the ambient noise and the analog signal corresponding to the noise-reducing sound, so that the analog filter can achieve the optimal response to the ambient noise, further improving the noise reduction effect.

[0113] The basic concepts have been described above. It is clear that the detailed disclosure above is merely illustrative and does not constitute a limitation of this specification. Although not explicitly stated herein, various modifications, improvements, and corrections may be made to this specification by those skilled in the art. Such modifications, improvements, and corrections are suggested in this specification and therefore remain within the spirit and scope of the exemplary embodiments described herein.

[0114] Furthermore, this specification uses specific terms to describe embodiments thereof. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic associated with at least one embodiment of this specification. Therefore, it should be emphasized and noted that references to "an embodiment," "one embodiment," or "an alternative embodiment" in different locations throughout this specification do not necessarily refer to the same embodiment. Moreover, certain features, structures, or characteristics in one or more embodiments of this specification can be appropriately combined.

[0115] Furthermore, unless expressly stated in the claims, the order of processing elements and sequences, the use of numbers and letters, or other names described in this specification are not intended to limit the order of the processes and methods described herein. Although various examples have been discussed in the foregoing disclosure of some embodiments of the invention that are currently considered useful, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments; rather, the claims are intended to cover all modifications and equivalent combinations that conform to the spirit and scope of the embodiments described herein. For example, while the system components described above can be implemented using hardware devices, they can also be implemented solely using software solutions, such as installing the described system on existing servers or mobile devices.

[0116] Similarly, it should be noted that, in order to simplify the description disclosed herein and thus aid in the understanding of one or more embodiments of the invention, the foregoing description of embodiments in this specification may sometimes combine multiple features into a single embodiment, drawing, or description thereof. However, this method of disclosure does not imply that the subject matter of this specification requires more features than those mentioned in the claims. In fact, the embodiments contain fewer features than all the features of a single embodiment disclosed above.

[0117] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used in the description of embodiments are modified in some examples with the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of range in some embodiments of this specification are approximate values, in specific embodiments, such values ​​are set as precisely as feasible.

[0118] For each patent, patent application, patent application publication, and other material, such as articles, books, specifications, publications, and documents, referenced in this specification, the entire contents of which are incorporated herein by reference. This excludes historical application documents that are inconsistent with or conflict with the content of this specification, as well as documents that limit the broadest scope of the claims in this specification (currently or subsequently appended to this specification). It should be noted that in the event of any inconsistency or conflict between the descriptions, definitions, and / or terminology used in the supplementary materials to this specification and the content of this specification, the descriptions, definitions, and / or terminology used in this specification shall prevail.

[0119] Finally, it should be understood that the embodiments described in this specification are merely illustrative of the principles of the embodiments described herein. Other variations may also fall within the scope of this specification. Therefore, alternative configurations of the embodiments described herein are intended to be illustrative rather than limiting, and should be considered consistent with the teachings of this specification. Accordingly, the embodiments described herein are not limited to those explicitly introduced and described herein.

Claims

1. An active noise cancellation frequency device, characterized in that, include: A loudspeaker used to produce noise-canceling sound; A microphone is used to collect ambient noise and the noise-reduced sound, and to generate a first analog signal; An analog filter is used to provide gain to the first analog signal and generate a second analog signal, the second analog signal driving the loudspeaker to produce the noise-reduced sound; A first analog adder is configured to generate a third analog signal based on the first analog signal, the second analog signal, and a secondary response corresponding to the second analog signal, wherein the secondary response is the response from the speaker to the microphone; as well as The processing circuit includes a first analog-to-digital converter (ADC) and a third ADC. The first ADC is used to sample the first analog signal to generate a first digital signal; the third ADC is used to sample the third analog signal to generate a third digital signal; the processing circuit is further used to send control commands to the analog filter based on the first digital signal and the third digital signal to adjust the gain and phase shift of the analog filter.

2. The active noise cancellation frequency device according to claim 1, characterized in that, The processing circuit adjusts the gain and phase shift of the analog filter, including: Within a specific time range, as the amplitude of the first analog signal changes, the processing circuit controls the analog filter to dynamically adjust its gain.

3. The active noise cancellation device according to claim 1, characterized in that, The processing circuit includes a first analog-to-digital converter and a second analog-to-digital converter; The first analog-to-digital converter samples the first analog signal to generate a first digital signal, and the second analog-to-digital converter samples the second analog signal to generate a second digital signal; The processing circuit sends control commands to the analog filter, including: The processing circuit sends control commands to the analog filter based on the first digital signal and the second digital signal.

4. The active noise cancellation frequency device according to claim 3, characterized in that, The analog filter includes a switching gating circuit and a response regulator. The switching gating circuit adjusts the resistance or capacitance of the response regulator according to the control command to change the amplitude frequency response and phase frequency response of the analog filter.

5. The active noise cancellation frequency device according to claim 4, characterized in that, The response regulator includes one or more phase modulation units, each phase modulation unit including at least one adjustable resistor or at least one adjustable capacitor; The switch gate control circuit adjusts the resistance or capacitance value of the response regulator according to the control command, including: The switch gate control circuit adjusts the resistance value of the adjustable resistor or the capacitance value of the adjustable capacitor according to the control command.

6. The active noise cancellation device according to claim 1, characterized in that, It also includes a fixing structure that fixes the speaker and the microphone in a position near the user's ear without blocking the user's ear canal.

7. The active noise cancellation device according to claim 6, characterized in that, It also includes a first analog adder, a third analog-to-digital converter, and a fourth analog-to-digital converter, wherein, The first analog adder is used to generate a third analog signal based on the first analog signal, the second analog signal, and a secondary response corresponding to the second analog signal; the secondary response is the response from the speaker to the microphone. The third analog-to-digital converter samples the third analog signal to generate a third digital signal; The fourth analog-to-digital converter samples the second analog signal after adding the secondary response to generate a fourth digital signal; The processing circuit sends control commands to the analog filter, including: The processing circuit determines the fifth digital signal based on the third digital signal and the transfer function between the user's ear canal and the microphone; The processing circuit sends control commands to the analog filter based on the fourth digital signal and the fifth digital signal.

8. The active noise cancellation device according to claim 7, characterized in that, The transfer function between the user's ear canal and the microphone is obtained through experimental testing, or based on a statistical model or a neural network model.

9. The active noise cancellation device according to any one of claims 1-8, characterized in that, The processing circuit periodically sends control commands to the analog filter.

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