CN116612774A - Active noise reduction audio equipment - Google Patents
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- G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
- G10L21/00—Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility
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- G10L21/00—Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility
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Abstract
The embodiment of the specification discloses active noise reduction audio equipment. The apparatus comprises: a speaker, a microphone, an analog filter, and a processing circuit. The speaker is used for generating noise reduction sounds, the microphone is used for collecting environmental noise and noise reduction sounds, and a first analog signal is generated. The analog filter is used for providing gain for the first analog signal and generating a second analog signal, wherein the second analog signal drives the loudspeaker to generate noise reduction sound. The processing circuit is used for sending control instructions to the analog filter according to the first analog signal and the second analog signal so as to adjust the gain and the phase shift of the analog filter. According to the method and the device, the amplitude and the phase of the analog signal are adjusted through the analog filter, noise reduction sound is generated, time delay brought by signal conversion links and digital filter processing can be reduced, noise reduction response can be timely carried out on the audio equipment, and therefore noise reduction effect is improved.
Description
Technical Field
The present disclosure relates to the field of audio noise reduction, and in particular, to an active noise reduction audio device.
Background
Ambient noise is often reduced in audio devices by active noise reduction techniques. For example, the audio device may collect and analyze external environmental noise through the microphone to generate noise reduction sound with opposite phase to the external environmental noise, so that when sound emitted by the audio device enters the human ear, the external environmental noise and the noise reduction sound cancel each other, and a noise elimination effect is achieved.
In audio equipment, a digital filter bank is generally adopted to adjust the gain and the phase of an audio signal, but the digital filter bank often generates larger time delay when processing the signal, so that external environment noise cannot be processed in time, and noise reduction response is too slow, and the noise reduction effect of the audio equipment is affected.
Therefore, there is a need for an active noise reduction audio device that can respond quickly.
Disclosure of Invention
One of the embodiments of the present specification provides an active noise reduction audio device. The apparatus includes: a speaker, a microphone, an analog filter, and a processing circuit. The speaker is used for generating noise reduction sounds, the microphone is used for collecting environmental noise and noise reduction sounds, and a first analog signal is generated. The analog filter is used for providing gain for the first analog signal and generating a second analog signal, wherein the second analog signal drives the loudspeaker to generate noise reduction sound. The processing circuit is used for sending control instructions to the analog filter according to the first analog signal and the second analog signal so as to adjust the gain and the phase shift of the analog filter.
According to the embodiment of the specification, the amplitude and the phase of the analog signal are adjusted by using the analog filter, and noise reduction sound is generated by using the amplitude and the phase of the analog signal, so that the time delay brought by signal conversion (such as digital-to-analog conversion and the like) links and digital filter processing can be reduced, and noise reduction response can be timely carried out on the audio equipment, and the noise reduction effect is improved.
In addition, the active noise reduction audio device provided in the embodiment of the present disclosure may further include a processing circuit, where the processing circuit adjusts the gain and the phase shift of the analog filter according to the analog signals corresponding to the environmental noise and the noise reduction sound, so that the analog filter achieves an optimal response to the environmental noise, and further improves the noise reduction effect.
In some embodiments, the processing circuit adjusts the gain and phase shift of the analog filter, comprising: the processing circuit controls the analog filter to dynamically adjust the gain of the analog filter as the amplitude of the first analog signal changes within a specific time range.
In some alternative embodiments, 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 instructions to the analog filter, comprising: the processing circuit sends control instructions to the analog filter according to the first digital signal and the second digital signal.
In some embodiments, the analog filter includes a switching gate control circuit and a response regulator, the switching gate control circuit adjusting a resistance or capacitance of the response regulator according to the control command to change an amplitude-frequency response and a phase-frequency response of the analog filter.
In some embodiments, the response modifier comprises one or more phase modulation units, each phase modulation unit comprising at least one adjustable resistor or at least one adjustable capacitor. The switch door control circuit adjusts the resistance value or the capacitance value of the response regulator according to the control instruction, and comprises: 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 instruction.
In some alternative embodiments, the active noise reduction audio device further comprises a first analog adder, a first analog-to-digital converter, and a third analog-to-digital converter. The first analog adder is used for generating a third analog signal according to the first analog signal, the second analog signal and a secondary response corresponding to the second analog signal, wherein the secondary response is a response from the loudspeaker to the microphone. The first analog-to-digital converter samples the first analog signal to generate a first digital signal and the third analog-to-digital converter samples the third analog signal to generate a third digital signal. And the processing circuit sends control instructions to the analog filter, comprising: the processing circuit sends a control instruction to the analog filter according to the first digital signal and the third digital signal.
In some embodiments, the active noise reduction audio device further comprises a securing structure that secures the speaker and microphone, respectively, in a position near the user's ear and not occluding the user's ear canal.
In some alternative embodiments, the active noise reduction audio device further comprises a first analog adder, a third analog-to-digital converter, and a fourth analog-to-digital converter. The first analog adder is used for generating a third analog signal according to the first analog signal, the second analog signal and a secondary response corresponding to the second analog signal, wherein the secondary response is a response from the loudspeaker to the microphone. The third analog-to-digital converter samples the third analog signal to generate a third digital signal, and the fourth analog-to-digital converter samples the second analog signal after adding the secondary response to generate a fourth digital signal. And the processing circuit sends control instructions to the analog filter, comprising: the processing circuit determines a fifth digital signal according to the third digital signal and a transfer function between the user's ear canal and the microphone, and sends a control instruction to the analog filter according to the fourth digital signal and the fifth digital signal.
In some embodiments, the transfer function between the microphone and the ear canal of the user is obtained through experimental testing, or is obtained based on a statistical model or a neural network model.
In some embodiments, the processing circuitry periodically sends control instructions to the analog filter.
Drawings
The present specification will be further elucidated by way of example embodiments, which will be described in detail by means of the accompanying drawings. The embodiments are not limiting, in which like numerals represent like structures, wherein:
FIG. 1 is a block diagram of an active noise reduction audio device according to some embodiments of the present description;
FIG. 2 is a simplified schematic structural diagram of an active noise reduction audio device according to some embodiments of the present description;
fig. 3A is a schematic diagram of a phase modulation unit according to some embodiments of the present disclosure;
FIG. 3B is a schematic diagram of a phase modulation unit according to some embodiments of the present disclosure;
FIG. 4 is a schematic diagram of an active noise reduction audio device according to some embodiments of the present description;
FIG. 5 is a schematic diagram of an active noise reduction audio device according to some embodiments of the present description;
fig. 6 is a schematic structural diagram of an active noise reduction audio device according to some embodiments of the present description.
Detailed Description
In order to more clearly illustrate the technical solutions of the embodiments of the present specification, the drawings that are required to be used in the description of the embodiments will be briefly described below. It is apparent that the drawings in the following description are only some examples or embodiments of the present specification, and it is possible for those of ordinary skill in the art to apply the present specification to other similar situations according to the drawings without inventive effort. Unless otherwise apparent from the context of the language or otherwise specified, like reference numerals in the figures refer to like structures or operations.
It will be appreciated that "system," "apparatus," "unit" and/or "module" as used herein is one method for distinguishing between different components, elements, parts, portions or assemblies at different levels. However, if other words can achieve the same purpose, the words can be replaced by other expressions.
As used in this specification and the claims, the terms "a," "an," "the," and/or "the" are not specific to a singular, but may include a plurality, unless the context clearly dictates otherwise. In general, the terms "comprises" and "comprising" merely indicate that the steps and elements are explicitly identified, and they do not constitute an exclusive list, as other steps or elements may be included in a method or apparatus.
A flowchart is used in this specification to describe the operations performed by the system according to embodiments of the present specification. It should be appreciated that the preceding or following operations are not necessarily performed in order precisely. Rather, the steps may be processed in reverse order or simultaneously. Also, other operations may be added to or removed from these processes.
The active noise reduction audio device of one or more embodiments of the present disclosure may provide noise reduction according to ambient noise, so as to be applied to various scenes in which ambient noise interference needs to be avoided, for example, noise reduction may be provided for an audio output device (such as a sound device, an earphone, etc.), so as to improve the quality of audio output; as another example, noise reduction sounds may be provided for audio input devices (e.g., microphones, pickups, etc.) to improve the quality of audio recordings. In some embodiments, the active noise reduction audio device may adjust the size of the noise reduction sound output in real time according to the size of the environmental noise, so that the active noise reduction audio device may optimally respond to the environmental noise, and improve the noise reduction effect.
In some embodiments, the active noise reduction audio device may be a feedback active noise reduction device or a feedforward active noise reduction device. The microphone in the feedforward active noise reduction device mainly receives environmental noise, and then the loudspeaker generates corresponding noise reduction sound to reduce noise. The microphone in the feedback type active noise reduction equipment can collect the noise reduction sound generated by the environmental noise and the loudspeaker at the same time, and the processing circuit generates a feedback signal for driving the loudspeaker to adjust the noise reduction sound according to the superposition effect of the environmental noise and the noise reduction sound, so that the noise reduction effect is achieved. In some embodiments, the active noise reduction audio device may also employ other noise reduction methods, such as feedforward and feedback combined active noise reduction.
Currently, active noise reduction audio devices may include a digital filter bank, an analog-to-digital converter, and a digital-to-analog converter. The analog-to-digital converter can convert sound (environment noise or sound obtained by superposing the environment noise and the noise-reducing sound) received by the microphone into a digital signal, the digital filter bank processes the digital signal to generate a corresponding noise-reducing digital signal, and the digital-to-analog converter converts the noise-reducing digital signal into an analog signal and outputs the analog signal through the loudspeaker so as to offset the environment noise. However, a mode of adopting a digital filter bank to process signals can generate larger time delay, so that the active noise reduction equipment can not process external environment noise in time easily, the noise reduction response is too slow, and the real-time noise reduction effect of the audio equipment is affected.
According to the active noise reduction audio device provided by the embodiment of the specification, the analog filter is adopted to directly process (e.g. gain or phase shift) the analog signal corresponding to the noise reduction sound, so that the links of signal conversion (such as digital-to-analog conversion and the like) and the time delay brought by the digital filter processing can be reduced, the audio device can timely perform noise reduction processing, and the noise reduction effect is improved.
In addition, the active noise reduction audio device provided in the embodiment of the present disclosure may further include a processing circuit, where the processing circuit adjusts the gain and the phase shift of the analog filter according to the analog signals corresponding to the environmental noise and the noise reduction sound, so that the analog filter achieves an optimal response to the environmental noise, and further improves the noise reduction effect.
Fig. 1 is a block diagram of an active noise reduction audio device according to some embodiments of the present description. In some embodiments, as shown in fig. 1, an active noise reduction audio device 100 may include: speaker 110, microphone 120, analog filter 130, and processing circuit 140.
Speaker 110 is a transducer device that converts electrical signals into acoustic signals. In some embodiments, the active noise reduction audio device 100 is an open-ended earphone and the speaker 110 may be positioned near the user's ear but not in a location that blocks the user's ear. For example, the support structure of the open earphone may secure the speaker (or a housing accommodating the speaker) in a hanging or clamping manner on the peripheral side of the user's pinna (e.g., the front side of the tragus) or inside the outline of the pinna (e.g., near the triangular fossa). In some embodiments, the active noise reduction audio device 100 is a non-open earphone (e.g., an in-ear earphone or earmuff earphone), and the support structure of the non-open earphone may position the speaker 110 within the user's ear canal or within an enclosed space formed by the housing structure around the user's ear. In some embodiments, the support structure may be a mount for an ear-hang type bracket, a head-hang type bracket, or the like. Illustratively, the active noise reduction audio device 100 may be an external earphone, a speaker, a bone conduction earphone, an air conduction earphone, an AR device, a VR device, a headphone audio device, a car audio device, a hearing aid, or the like, or alternatively, the active noise reduction audio device 100 may be part of an in-car audio system or an in-room audio system for actively reducing noise at a specific location in space.
In some embodiments, the speaker 110 may output the noise reduction sound having an opposite phase to the ambient noise so that the noise reduction sound may cancel the ambient noise. Further, the noise reduction sound may be 180 degrees out of phase with the ambient noise at the user's ear canal. In some embodiments, speaker 110 may also output other audio, such as alert sounds, audio played according to user needs, and the like.
Microphone 120 is a transducer device that converts acoustic signals into electrical signals. In some embodiments, the microphone 120 may collect the ambient noise and the noise-reducing sound at the same time, and transmit the collected sound to the analog filter 130 or the processing circuit 140 for processing, and feedback the magnitude and phase of the noise-reducing sound, so that the sound collected by the microphone 120 is as small as possible, and the microphone may be referred to as a feedback microphone. The feedback microphone may be positioned close to the user's ear canal so that the received sound is as close as possible to the sound actually received by the user's ear. In some embodiments, the microphone 120 may be used primarily to collect ambient noise, with as little noise reduction as possible from the speaker 110, at which point the microphone may be referred to as a feedforward microphone. To reduce the impact of the speaker 110 on the feedforward microphone, a physical structure may be provided between the feedforward microphone and the speaker 110 to isolate sound transmission, or the feedforward microphone may be located away from the speaker 110, or the feedforward microphone may be located near an acoustic zero of the speaker 110.
In some embodiments, when the microphone is a feedback microphone, ambient noise and noise-reducing sound may be collected simultaneously and a first analog signal corresponding to the ambient noise and noise-reducing sound may be generated. The amplitude of the first analog signal may reflect the degree to which the ambient noise and the noise reducing sound cancel each other. In order to achieve the desired noise reduction effect, the amplitude of the first analog signal should be as small as possible, even down to 0.
It should be noted that, in comparison with a closed or semi-open audio device, the microphone is not disposed at the ear canal of the user in the open audio device, so that the sound received by the ear canal of the user is inconsistent with the sound received by the microphone. In some embodiments, a transfer function may be constructed between the microphone and the user's ear canal, representing the correspondence of the sound signals received by the user's ear canal to the sound signals received by the microphone. For a specific implementation of the open audio device, reference may be made to the following related content of fig. 6, which is not described herein.
To better describe the relationship between the speaker 110 and the microphone 120, fig. 2 depicts a specific implementation of the speaker and microphone by way of example.
Fig. 2 is a simplified schematic structural diagram of an active noise reduction audio device according to some embodiments of the present description.
As shown in fig. 2, y (t) represents an analog signal corresponding to the noise reduction sound, also referred to as a second analog signal, received by the speaker 110, from which the speaker 110 can generate the noise reduction sound; p (t) represents the corresponding analog signal when ambient noise is received by microphone 120; e (t) is a first analog signal generated by the microphone 120 from the environmental noise and the noise reduction sound received simultaneously. Thus, the relationship of the three signals can be expressed as:
e(t)＝p(t)+y(t). (1)
in some embodiments, in order to make the generated noise reduction sound cancel with the environmental noise, the first analog signal e (t) is subjected to a certain process (such as a process of shifting a phase by a shifter and amplifying by an amplifier, etc.), and then the second analog signal y (t) is generated. In an ideal case, the second analog signal y (t) and the analog signal p (t) corresponding to the ambient noise cancel each other out, thereby realizing that the amplitude of the first analog signal e (t) is reduced to 0. It should be noted that the description of the processing of the first analog signal e (t) is for illustrative purposes only and does not limit the corresponding modifications made by those skilled in the art on the basis of the principle of understanding. For example, the first analog signal e (t) may be subjected to phase shifting or amplifying by different electronic devices such as an amplifier and a phase shifter, or the phase shifting and amplifying of the first analog signal e (t) may be simultaneously performed by the same electronic device (for example, an analog filter).
Analog filter 130 is a circuit device that filters an analog or continuous time signal. In some embodiments, analog filter 130 may perform signal processing on the analog signal. For example, the analog filter 130 may simultaneously phase shift and amplify the analog signal to adjust the phase and amplitude of the analog signal.
In some embodiments, the analog filter 130 may be used to provide gain to the first analog signal and generate a second analog signal that drives the speaker 110 to produce a noise-reduced sound. Illustratively, with continued reference to FIG. 2 above, the gain of the analog filter 130 may be represented in the time domain as H (t), in the frequency domain as H(s), and the analog filter 130 may provide the gain H (t) to the first analog signal e (t) and generate the second analog signal y (t). Thus, the relationship of the three signals can be expressed in the time domain as:
y(t)＝e(t)*h(t), (2)
where is the convolution operation. In some embodiments, according to the above formula (1) and formula (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 the frequency domain, respectively, may be expressed as:
where E (S) is a representation of the first analog signal in the frequency domain, P (S) is a representation of the analog signal corresponding to the ambient noise in the frequency domain, and H (S) is a gain of the analog filter 130 in the frequency domain.
As shown in equation (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, the closer 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 environmental noise may cancel each other). Thus, the active noise reduction audio device 100 may set the analog filter 130 having a large gain H (S) to improve the noise reduction effect.
In some embodiments, the analog filter 130 may adjust its gain and phase shift according to control instructions from the processing circuit 140 to avoid unstable noise reduction effects of the active noise reduction audio device 100 caused by excessive or insufficient gain. Illustratively, when the active noise reduction audio device 100 is in the initial state, the value of the first analog signal is mainly derived from the contribution of the ambient noise (i.e., the second analog signal in the initial state is smaller or approximately 0), at which time the analog filter 130 may be set to have a smaller gain, avoiding that the first analog signal is excessively amplified and the second analog signal with an excessively large amplitude is generated at the next moment, resulting in that the speaker emits an excessively large noise reduction sound, which causes the device to be damaged. The processing circuit 140 may control the analog filter 130 to dynamically adjust its gain as the amplitude of the first analog signal varies over a particular time frame. For example, the gain of the analog filter 130 may be increased over a period of time from when the active noise reduction audio device 100 is in an initial state as the amplitude of the first analog signal decreases, thereby avoiding that the second analog signal may not cancel each other out with the analog signal corresponding to the ambient noise due to too little gain. For specific adjustment of the analog filter 130, reference may be made to the following related contents of the processing circuit, which will not be described herein. In some embodiments, during operation of the active noise reduction audio device 100, when the ambient noise fluctuates, the analog filter 130 may also dynamically adjust the gain of the analog filter 130 under the control of the processing circuit 140, so as to adapt to the change of the ambient noise. For example, at some point, when the environmental noise becomes larger, the amplitude of the first analog signal may become larger, and the processing circuit 140 may control the analog filter 130 to reduce the gain thereof, so as to avoid damage to the speaker caused by excessive amplification of the first analog signal.
In some embodiments, the analog filter 130 may include a switching gate control circuit and a response regulator, where the switching gate control circuit adjusts a resistance value or a capacitance value of the response regulator according to a control instruction to change an amplitude-frequency response and a phase-frequency response of the analog filter 130, so as to implement a phase shifting process and/or an amplifying process on the first analog signal.
In some embodiments, the switch gate control circuit may adjust the resistance or capacitance of the response regulator via an analog switch. Further, the analog switch can change the channel of the response regulator through position transformation to adjust the resistance value or the capacitance value of the response regulator according to the different resistance values or capacitance values of different channels of the response regulator. Illustratively, the response modifier includes a potentiometer, and the resistance of the response modifier can be changed by changing the position of the analog switch to change the path of the potentiometer to the circuit.
In some embodiments, the switch gating circuit may adjust the state of the switch itself according to the control instructions. In an exemplary embodiment, the switch gating circuit may adjust the position of the analog switch according to the frequency of the pulse signal when the control command is the pulse signal. In some embodiments, the switch gate control circuit may periodically receive a control signal from the processing circuit 140, and details of implementation of the control signal may be referred to in the following processing circuit and will not be described herein.
The response modifier may be a circuit device that processes signals. For example, the response regulator may perform signal processing (e.g., phase shifting, amplifying, etc.) on the input first analog signal to obtain the second analog signal. In some embodiments, the resistance or capacitance of the response modifier may affect the amplitude-frequency response and the phase-frequency response of the analog filter 130, thereby affecting the effectiveness of the signal processing. For example, in the case that the first analog signal does not change, but the resistance or capacitance of the response regulator changes, the amplitude-frequency response and the phase-frequency response of the analog filter 130 are changed, so that the amplitude and the phase of the second analog signal output by the analog filter 130 are changed. The specific implementation of the response regulator will be described in detail below using a phase modulation unit as an example.
In some embodiments, the response modifier may include one or more phase modulation units, each of which may include at least one adjustable resistor or at least one adjustable capacitor. Correspondingly, the switch door control circuit can adjust the resistance value of the adjustable resistor or the capacitance value of the adjustable capacitor according to the control instruction.
The phase modulation unit may be a circuit set of a plurality of parameter-adjustable devices. In some embodiments, the response modifier may change the resistance or capacitance of the response modifier by changing the resistance of the adjustable resistor or the capacitance of the adjustable capacitor in the phase modulation unit. The adjustable resistor can be a slide rheostat, a potentiometer, a resistor and the like, and the specific type of the adjustable resistor can be selected according to the type of the switch door control circuit. The adjustable capacitor can be a patch adjustable capacitor, a plug-in adjustable capacitor and the like, and the specific type of the adjustable capacitor can be selected according to the type of the switch door control circuit. Fig. 3A and 3B illustrate by way of example a specific implementation of a phase modulation unit.
Fig. 3A is a schematic diagram of a phase modulation unit according to some embodiments of the present disclosure.
As shown in fig. 3A, phase modulation unit 310 may include a capacitor C1, a resistor R1, and a voltage follower Q1. The capacitor C1 is connected with the resistor R1 in series, one end of the capacitor C1 is grounded, the connection point of the capacitor C1 and the resistor R1 is connected with the non-inverting input end of the voltage follower Q1, the inverting input end of the voltage follower Q1 is connected with the output end, and the phase modulation unit 310 can transmit a signal Ui 1 Signal processing is carried out to obtain a signal Uo 1 . In the embodiment of the present disclosure, the voltage follower Q1 can avoid the influence of the post-stage circuit on the phase modulation unit 310, and maintain the stable operation of the phase modulation unit 310.
Fig. 3B is a schematic diagram of a phase modulation unit according to some embodiments of the present disclosure.
As shown in fig. 3B, a plurality of phase modulation units 320 are connected in series, wherein one phase modulation unit 320 may include a capacitor (e.g., capacitor C2) and a resistor (e.g., resistor R2) connected in series, and the resistor (e.g., capacitor C2) in the phase modulation unit 320 is connected in series with the resistor (e.g., resistors R3, R4) of the other phase modulation unit 320, and the capacitor (e.g., capacitor C2) in the phase modulation unit 320 is connected in parallel with the capacitor (e.g., capacitors C3, C4) of the other phase modulation unit 320. Multiple phase modulation units 320 may mix signal Ui 2 Signal processing is carried out to obtain a signal Uo 2 。
In some embodiments, the range of the phase frequency response of the response regulator may be adjusted by adjusting the number of phase modulation units 320 in series. Illustratively, the greater the number of phase modulation units 320 in series, the greater the range of phase frequency response of the response regulator.
Thus, the transfer function of phase modulation units (e.g., phase modulation units 310, 320 described above) may be expressed as:
wherein, R is the resistance of the resistor in the phase modulation unit, C is the capacitance of the capacitor in the phase modulation unit, and the phase frequency response of one phase modulation unit can be expressed as: -arctan (wRC), the range of the phase-frequency response may be [ -90 °,0 ° ].
In some embodiments, the capacitances C1-C4 may be tunable capacitances, or the resistances R1-R4 may be tunable resistances. Note that, fig. 3A to 3B only show that the resistors R1 to R4 are adjustable resistors. The phase frequency response of the phase modulation unit can be changed within [ -90 degrees, 0 degrees ] by adjusting the capacitance value of the adjustable capacitor (such as the capacitor C1-C4) or the resistance value of the adjustable resistor (such as the resistor R1-R4). Correspondingly, the switch door control circuit can adjust the access circuit by using an analog switch corresponding to the adjustable device according to the control instruction, so as to realize the adjustment of the capacitance value of the capacitors C1-C4 or the resistance value of the resistors R1-R4.
In the embodiment of the present disclosure, the amplitude-frequency response and the phase-frequency response of the analog filter 130 can be adjusted by matching the switching gate control circuit with the response adjuster, so that the gain provided by the analog filter 130 at a specific moment is prevented from being too large or too small, so that the optimal response of the analog filter 130 to the environmental noise is achieved, and the noise reduction effect of the active noise reduction audio device 100 is improved.
The processing circuit 140 may be a circuit unit having a data processing control function. In some embodiments, processing circuitry 140 may include circuit modules such as an integrated circuit ASIC, a programmable gate array (Field Programmable Gate Array, FPGA), a complex programmable logic device (Complex Programmable logic device, CPLD), a micro control unit (Microcontroller Unit, MCU), an arithmetic logic unit (Central Processing Unit, CPU), a digital signal processor (Digital Signal Process, DSP), or a graphics processor (graphics processing unit, GPU).
In some embodiments, the processing circuit 140 may control the analog filter 130 to dynamically adjust its gain as the amplitude of the first analog signal changes over a particular time frame. For example, the specific time range may be a time period after the active noise reduction audio device 100 starts to operate, and as the active noise reduction audio device 100 starts to operate, the processing circuit 140 may send a control instruction with the amplitude of the first analog signal decreasing, and gradually increase the gain of the analog filter 130, so as to keep the amplitude of the second analog signal close to the analog signal corresponding to the environmental noise, and improve the noise reduction effect of the device.
It should be noted that, when the active noise reduction audio device 100 is in the initial state (i.e., the state in which the active noise reduction audio device 100 starts to operate), since the external environmental noise is mostly not cancelled, the amplitude of the first analog signal is larger, at this time, the processing circuit 140 may issue a control instruction to control the analog filter 130 to have a smaller gain, so as to avoid the amplitude of the second analog signal from being too large, and ensure that the active noise reduction audio device 100 can stably operate in the initial state.
In some embodiments, the processing circuit 140 may send control instructions to the analog filter 130 to adjust the gain and phase shift of the analog filter 130 based on the first analog signal and the second analog signal.
The first analog signal may reflect the degree to which the ambient noise and the noise reduction sound cancel each other, and the second analog signal may reflect the magnitude of the noise reduction sound. In some embodiments, the control instructions may be high level signals or pulse signals, etc., and the particular type of control instruction may be selected based on the type of processing circuitry 140.
In some embodiments, processing circuitry 140 may adjust the gain and phase shift of analog filter 130 by adjusting the frequency of the control instructions. Fig. 4 illustrates a specific implementation of the processing circuit 140 in detail by way of example.
Fig. 4 is a schematic structural diagram of an active noise reduction audio device 100 according to some embodiments of the present description.
As shown in fig. 4, y (t) represents the second analog signal, e (t) represents the first analog signal, and the processing circuit 140 may calculate the coefficients (such as gain and phase shift) of the analog filter 130 according to the first analog signal e (t) and the second analog signal y (t), calculate the amplitude-frequency response and the phase-frequency response of the analog filter 130, generate control instructions corresponding to the amplitude-frequency response and the phase-frequency response, and send the control instructions to the analog filter 130. The analog filter 130 may adjust its own gain and phase shift based on the control command such that the actual gain and phase shift of the analog filter 130 approximates the calculated gain and phase shift. The specific implementation of the analog filter 130 may be referred to in the above description of fig. 3A-3B, and will not be described in detail herein.
In the embodiment of the present disclosure, the processing circuit 140 generates the control signal according to the analog signal corresponding to the environmental noise and the noise reduction sound, so as to adjust the gain and the phase shift of the analog filter 130, so that the analog filter 130 achieves the optimal response to the environmental noise, and further improves the noise reduction effect.
In some embodiments, processing circuitry 140 may include a first analog-to-digital converter that samples a first analog signal to generate a first digital signal and a second analog-to-digital converter that samples a second analog signal to generate a second digital signal. Correspondingly, the processing circuit 140 may send control instructions to the analog filter 130 according to the first digital signal and the second digital signal.
In some embodiments, the analog-to-digital converter (e.g., first analog-to-digital converter, second analog-to-digital converter) may sample the analog signal (e.g., first analog signal, second analog signal) according to a predetermined sampling rate to generate a discrete digital signal (e.g., first digital signal, second digital signal). Correspondingly, the processing circuit 140 may generate the control signal according to the first digital signal and the second digital signal. Illustratively, as shown in FIG. 4, the first analog-to-digital converter 141 samples the first analog signal e (t) to generate a first digital signal e (n), and the second analog-to-digital converter 142 samples the second analog signal y (t) to generate a second digital signal y (n).
In some implementations, the processing circuit 140 may calculate coefficients (e.g., gain and phase shift) of the analog filter 130 from the first digital signal and the second digital signal based on a noise reduction algorithm such as an adaptive filtering algorithm (Least Mean Square, LMS), a filtered x least mean square algorithm (FXLMS), or the like, to generate control instructions corresponding to the coefficients.
In the embodiment of the present disclosure, the analog-to-digital converter converts the analog signal into the digital signal, so that 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 can be compatible, and the analog-to-digital combination can be implemented, thereby widening the application scenario of the active noise reduction audio device 100.
Because of the time required for analog-to-digital conversion and signal processing, in some embodiments, processing circuitry 140 may periodically send control instructions to the analog filter 130. Correspondingly, the switching gate control circuit can adjust the resistance or capacitance of the response regulator in each period to regulate the amplitude-frequency response and the phase-frequency response of the analog filter 130.
In some embodiments, the processing circuit 140 may determine the period of sending the control command based on one or more delay-affecting factors such as the sampling rate of the analog-to-digital converter 130 and the time of signal conversion, the switch gate update time, and the time the processing circuit 140 processes the signal. For example, when the sampling rate of the analog-to-digital converter is 16kHz, and the switching gate circuit needs to update point by point about 0.06ms, the analog filter 130 needs to process the signal for 1ms, and the analog-to-digital conversion and the switching gate circuit needs to delay for about 5ms, it is determined that the period of sending the control command may be 1s. The specific time parameters provided above are referred to by way of example only and are not specifically limited in this specification.
In some embodiments, processing circuitry 140 may cease sending control instructions to analog filter 130 to cease regulating the amplitude-frequency response and the phase-frequency response of analog filter 130 when active noise reduction audio device 100 is operating stably. Further, the processing circuit 140 may stop sending the control command to the analog filter 130 when the amplitude of the first analog signal is within the preset amplitude range. When the amplitude of the first analog signal is within the preset amplitude range, it is reflected that the first analog signal is close to 0, that is, it may be reflected that the active noise reduction audio device 100 is in an ideal state of active noise reduction, and the operation is stable.
In some embodiments, as shown in fig. 4, the active noise reduction audio device 100 may further include an amplifier 150, and the amplifier 150 may amplify the first analog signal e (t) in conjunction with the analog filter 130. In some embodiments, the active noise reduction audio device 100 may not provide the amplifier 150, and may amplify the first analog signal e (t) only through the analog filter 130.
In some embodiments, the active noise reduction audio device 100 may compensate for the secondary response because the presence of the secondary channel's response in the audio device may affect the noise reduction effect. The secondary response is a response of a secondary channel in the audio device that may reflect the effect of the sound transfer path from the speaker to the microphone on the sound signal. Fig. 5 illustrates by way of example a specific implementation of compensating for the secondary response.
Fig. 5 is a schematic structural diagram of an active noise reduction audio device 100 according to some embodiments of the present description.
As shown in fig. 5, y (t) represents a second analog signal,representing the secondary response, i.e. the transfer function of the loudspeaker to the microphone +.>Representing a secondary response signal, which can be understood as adding a secondary response +.>A second analog signal y (t) after.
An analog adder is an electronic device that operates on a plurality of analog signals. In some embodiments, the analog adder may be an operational amplifier based adder circuit, such as an inverting adder circuit, an in-phase adder circuit, or the like. In some embodiments, the first analog adder may generate a third analog signal to compensate for the secondary response based on adding the first analog signal and the inverted secondary response signal. The third analog signal may reflect the sound wave after the cancellation of the environmental noise and the noise reduction sound, and the superimposed sound wave of the noise reduction sound inverted after passing through the secondary channel, that is, the environmental noise after the secondary response compensation.
By way of example, with continued reference to fig. 5 above,the analog signal corresponding to the environmental noise after the secondary response compensation, that is, the third analog signal outputted from the analog adder 160 is represented. In some embodiments, the relationship between the secondary response, the first analog signal, the second analog signal, and the third analog signal may be expressed as:
Wherein, the liquid crystal display device comprises a liquid crystal display device,for the third analog signal->For secondary response signals, i.e. adding response of loudspeaker to microphone +.>And e (t) is the first analog signal.
Correspondingly, in some embodiments, the first analog-to-digital converter samples the first analog signal to generate the first digital signal and the third analog-to-digital converter samples the third analog signal to generate the third digital signal. The processing circuit 140 may send control instructions to the analog filter 130 based on the first digital signal and the third digital signal to adjust the amplitude-frequency response and the phase-frequency response of the analog filter 130 while compensating for the secondary response.
Illustratively, with continued reference to FIG. 5 above, the first analog-to-digital converter 141 pairs the firstThe analog signal e (t) is sampled to generate a first digital signal e (n), and a third analog-to-digital converter 143 performs a third analog signalSampling to generate a third digital signalThe processing circuit 140 can be based on the first digital signal e (n) and the third digital signal +.>Coefficients of the analog filter 130 are determined. In the case of compensating for the secondary response, updating the coefficients of the analog filter 130 may be expressed as:
where w (n + 1) is the coefficient that analog filter 130 currently needs to update, w (n) is the coefficient that analog filter 130 last updated, E (n) is the first digital signal, which is the third digital signal +.>The adjustment value of the analog filter 130 may be obtained by performing signal processing on the first digital signal and the third digital signal through a noise reduction algorithm (such as LMS algorithm and FXLMS algorithm).
In some embodiments, processing circuitry 140, after determining the coefficients of analog filter 130 with compensation for the secondary response, sends control instructions to analog filter 130 to cause the actual gain and phase shift of analog filter 130 to approach the calculated updated coefficients so that analog filter 130 may approach the optimal response to ambient noise. The specific implementation of the analog filter 130 may be referred to in the above description of fig. 3A-3B, and will not be described in detail herein.
In the embodiment of the present disclosure, the secondary response is compensated by using the analog adder, so that signal compensation in the analog domain can be implemented, and delay caused by signal processing in the digital domain is avoided, thereby improving the accuracy of noise reduction while ensuring that the analog filter 130 can timely process external environmental noise, and further improving the noise reduction effect of the active noise reduction audio device 100.
In some embodiments, when the active noise reduction audio device 100 is an open audio device (i.e., the speaker is close to but not blocking the ear), the response of the channel between the user's ear canal and the microphone may affect the noise reduction effect, and thus the active noise reduction audio device 100 may construct a transfer function between the user's ear canal and the microphone to compensate, i.e., to perform an open response compensation.
The transfer function between the microphone and the user's ear canal may be indicative of the effect that sound is transferred between the microphone and the user's ear canal. In some embodiments, the transfer function between the microphone and the ear canal of the user may be obtained through experimental testing, or based on a statistical model or a neural network model.
Illustratively, the response H between speaker and microphone may be obtained by testing (e.g., artificial head testing, etc.) 1 And response H of speaker to user's ear canal 2 Based on response H again 1 And response H 2 Relationship betweenObtain the transfer function between the user's ear canal and the microphone +.>Alternatively, the response H between the speaker and the microphone can be based on 1 Running a statistical model (such as a Gaussian mixture model) or a neural network model to obtain a transfer function of model output>
In some embodiments, the active noise reduction audio device 100 may further include a first analog adder, a third analog-to-digital converter, and a fourth analog-to-digital converter. The fourth analog-to-digital converter may sample the secondary response signal to generate a fourth digital signal for signal processing by the processing circuit 140. The specific implementation of the analog adder and analog-to-digital converter may be referred to the relevant descriptions in fig. 4-5, and will not be repeated here. The processing circuit 140 may determine a fifth digital signal based on the third digital signal and a transfer function between the microphone and the ear canal of the user, and send control instructions to the analog filter 130 based on the fourth digital signal and the fifth digital signal to adjust the amplitude-frequency response and the phase-frequency response of the analog filter 130 while compensating for the secondary response and the open response. Further, in some embodiments, the processing circuit 140 may perform an addition operation on the fourth digital signal and the fifth digital signal to obtain a sixth digital signal, and send a control instruction to the analog filter 130 according to the third digital signal and the sixth digital signal.
The third digital signal may reflect the environmental noise after the secondary response compensation, the fourth digital signal may reflect the noise reduction sound after the secondary response is added, and the fifth digital signal may reflect the sound wave obtained after the noise reduction sound is subjected to the secondary response compensation under the influence of the open response. The sixth digital signal may reflect the sound wave obtained after the secondary response compensation and the open response compensation to the noise reduction sound. Fig. 6 illustrates in detail by way of example a specific implementation of open response compensation.
Fig. 6 is a schematic structural diagram of an active noise reduction audio device 100 according to some embodiments of the present description.
As shown in figure 6 of the drawings,representing the transfer function between the user's ear canal and the microphone, the fourth analog-to-digital converter 144 may be sensitive to the secondary response signal +.>Sampling to generate a fourth digital signal +.>Representing a fifth digital signal under the influence of an open response,>representing the sixth digital signal after the secondary response compensation and the open response compensation. Thus, according to the transfer function between the microphone and at the user's ear canal, the relationship between the fifth digital signal, the fourth digital signal and the third digital signal can be expressed as:
Wherein, the liquid crystal display device comprises a liquid crystal display device,for the sixth digital signal>For the fifth digital signal->Is the fourth digital signal, and +>* Representing convolution operations +.>A transfer function corresponding to the secondary response. That is, the processing circuit 140 may add +_to the fourth digital signal>And a fifth digital signal->Adding to obtain a sixth digital signal +.>The processing circuit 140 may also determine coefficients of the analog filter 130 based on the third digital signal and the sixth digital signal. In the case of compensating for the secondary response as well as the open response, updating the coefficients of the analog filter 130 can be expressed as:
where w '(n+1) is the coefficient that analog filter 130 needs to update this time, w' (n) is the coefficient that analog filter 130 updated last time,for the third digital signal->For the sixth digital signal>The adjustment value of the analog filter 130 may be obtained by performing signal processing on the third digital signal and the sixth digital signal through a noise reduction algorithm (such as LMS algorithm and FXLMS algorithm).
In some embodiments, processing circuitry 140, after determining the coefficients of analog filter 130 with compensation for the secondary response as well as the open response, sends control instructions to analog filter 130 to cause the actual gain and phase shift of analog filter 130 to approach the calculated updated coefficients, and analog filter 130 may approach the optimal response to ambient noise. The specific implementation of the analog filter 130 may be referred to in the above description of fig. 3A-3B, and will not be described in detail herein.
In the embodiment of the present disclosure, when the active noise reduction audio device 100 is an open audio device, the transfer function between the ear canal of the user and the microphone is compensated, so that the accuracy of noise reduction can be improved, and the noise reduction effect of the active noise reduction audio device 100 can be further improved.
Possible benefits of embodiments of the present description include, but are not limited to: (1) The analog filter is adopted to directly process (e.g. gain or phase shift) the analog signal corresponding to the noise reduction sound, so that the links of signal conversion (such as digital-to-analog conversion and the like) and the time delay brought by the digital filter processing can be reduced, the noise reduction response of the audio equipment can be timely carried out, and the noise reduction effect is improved. (2) The processing circuit adjusts the gain and the phase shift of the analog filter according to the analog signals corresponding to the environmental noise and the noise reduction sound so as to enable the analog filter to achieve the optimal response to the environmental noise and further improve the noise reduction effect.
While the basic concepts have been described above, it will be apparent to those skilled in the art that the foregoing detailed disclosure is by way of example only and is not intended to be limiting. Although not explicitly described herein, various modifications, improvements, and adaptations to the present disclosure may occur to one skilled in the art. Such modifications, improvements, and modifications are intended to be suggested within this specification, and therefore, such modifications, improvements, and modifications are intended to be included within the spirit and scope of the exemplary embodiments of the present invention.
Meanwhile, the specification uses specific words to describe the embodiments of the specification. Reference to "one embodiment," "an embodiment," and/or "some embodiments" means that a particular feature, structure, or characteristic is associated with at least one embodiment of the present description. Thus, it should be emphasized and should be appreciated that two or more references to "an embodiment" or "one embodiment" or "an alternative embodiment" in various positions in this specification are not necessarily referring to the same embodiment. Furthermore, certain features, structures, or characteristics of one or more embodiments of the present description may be combined as suitable.
Furthermore, the order in which the elements and sequences are processed, the use of numerical letters, or other designations in the description are not intended to limit the order in which the processes and methods of the description are performed unless explicitly recited in the claims. While certain presently useful inventive embodiments have been discussed in the foregoing disclosure, by way of various examples, it is to be understood that such details are merely illustrative and that the appended claims are not limited to the disclosed embodiments, but, on the contrary, are intended to cover all modifications and equivalent arrangements included within the spirit and scope of the embodiments of the present disclosure. For example, while the system components described above may be implemented by hardware devices, they may also be implemented solely by software solutions, such as installing the described system on an existing server or mobile device.
Likewise, it should be noted that in order to simplify the presentation disclosed in this specification and thereby aid in understanding one or more inventive embodiments, various features are sometimes grouped together in a single embodiment, figure, or description thereof. This method of disclosure, however, is not intended to imply that more features than are presented in the claims are required for the present description. Indeed, less than all of the features of a single embodiment disclosed above.
In some embodiments, numbers describing the components, number of attributes are used, it being understood that such numbers being used in the description of embodiments are modified in some examples by the modifier "about," approximately, "or" substantially. Unless otherwise indicated, "about," "approximately," or "substantially" indicate that the number allows for a 20% variation. Accordingly, in some embodiments, numerical parameters set forth in the specification and claims are approximations that may vary depending upon the desired properties sought to be obtained by the individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and employ a method for preserving the general number of digits. Although the numerical ranges and parameters set forth herein are approximations that may be employed in some embodiments to confirm the breadth of the range, in particular embodiments, the setting of such numerical values is as precise as possible.
Each patent, patent application publication, and other material, such as articles, books, specifications, publications, documents, etc., referred to in this specification is incorporated herein by reference in its entirety. Except for application history documents that are inconsistent or conflicting with the content of this specification, documents that are currently or later attached to this specification in which the broadest scope of the claims to this specification is limited are also. It is noted that, if the description, definition, and/or use of a term in an attached material in this specification does not conform to or conflict with what is described in this specification, the description, definition, and/or use of the term in this specification controls.
Finally, it should be understood that the embodiments described in this specification are merely illustrative of the principles of the embodiments of this specification. Other variations are possible within the scope of this description. Thus, by way of example, and not limitation, alternative configurations of embodiments of the present specification may be considered as consistent with the teachings of the present specification. Accordingly, the embodiments of the present specification are not limited to only the embodiments explicitly described and depicted in the present specification.
Claims (10)
1. An active noise reduction audio device, comprising:
A speaker for generating noise reduction sound;
the microphone is used for collecting environmental noise and the noise reduction sound and generating a first analog signal;
an analog filter for providing gain to the first analog signal and generating a second analog signal that drives the speaker to produce the noise reduction sound; and
and the processing circuit is used for sending a control instruction to the analog filter according to the first analog signal and the second analog signal so as to adjust the gain and the phase shift of the analog filter.
2. The active noise reduction audio device of claim 1, wherein the processing circuit adjusts a gain and a phase shift of the analog filter, comprising:
the processing circuit controls the analog filter to dynamically adjust its gain as the amplitude of the first analog signal changes over a particular time frame.
3. The active noise reduction audio device of claim 1, wherein the processing circuit comprises 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 instructions to the analog filter, comprising:
the processing circuit sends a control instruction to the analog filter according to the first digital signal and the second digital signal.
4. The active noise reduction audio device of claim 3, wherein the analog filter comprises a switching gate control circuit and a response regulator, the switching gate control circuit adjusting a resistance or a capacitance of the response regulator according to the control instruction to change an amplitude-frequency response and a phase-frequency response of the analog filter.
5. The active noise reduction audio device of claim 4, wherein the response modifier comprises one or more phase modulation units, each phase modulation unit comprising at least one adjustable resistor or at least one adjustable capacitor;
the switch door control circuit adjusts the resistance value or the capacitance value of the response regulator according to the control instruction, and the switch door control circuit comprises:
and 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 instruction.
6. The active noise reduction audio device of claim 1, further comprising a first analog adder, a first analog-to-digital converter, and a third analog-to-digital converter, wherein,
The first analog adder is configured to generate a third analog signal according to the first analog signal, the second analog signal, and a secondary response corresponding to the second analog signal, where the secondary response is a response from the speaker to the microphone;
the first analog-to-digital converter samples the first analog signal to generate a first digital signal;
the third analog-to-digital converter samples the third analog signal to generate a third digital signal;
the processing circuit sends control instructions to the analog filter, comprising:
the processing circuit sends a control instruction to the analog filter according to the first digital signal and the third digital signal.
7. The active noise reduction audio device of claim 1, further comprising a securing structure that secures the speaker and the microphone, respectively, in a position near the user's ear and not occluding the user's ear canal.
8. The active noise reduction audio device of claim 7, further comprising a first analog adder, a third analog-to-digital converter, and a fourth analog-to-digital converter, wherein,
the first analog adder is used for generating a third analog signal according to the first analog signal, the second analog signal and a secondary response corresponding to the second analog signal; the secondary response is a response of 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 instructions to the analog filter, comprising:
the processing circuit determines a fifth digital signal according to the third digital signal and a transfer function between the user's ear canal and the microphone;
the processing circuit sends a control instruction to the analog filter according to the fourth digital signal and the fifth digital signal.
9. The active noise reduction audio device of claim 8, wherein a transfer function between the microphone and at the user's ear canal is obtained through experimental testing or is obtained based on a statistical model or a neural network model.
10. The active noise reduction audio device of any of claims 1-9, wherein the processing circuitry periodically sends control instructions to the analog filter.
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