CN110610693B - Weighted mixed type active anti-noise system and controller - Google Patents
Weighted mixed type active anti-noise system and controller Download PDFInfo
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Abstract
The invention provides a weighted mixed type active anti-noise system, which comprises a reference microphone, an error microphone, a loudspeaker and a controller connected to the reference microphone, the error microphone and the loudspeaker. The controller comprises a feedforward noise reduction filtering module, a feedback noise reduction filtering module, a mixer, a noise detection module and a weight distribution module. The weight distribution module comprises one or a plurality of weight modulation units arranged between the error microphone and the feedback noise reduction filter module, when the noise detection module detects high-frequency noise from the reference microphone or the error microphone, a control signal is transmitted to the weight distribution module, and the weight distribution module reduces the weight value of the weight modulation unit so as to reduce the proportion of a feedback signal of the feedback noise reduction filter module.
Description
Technical Field
The present invention relates to an active noise immunity system and a controller, and more particularly, to a weighted hybrid active noise immunity system and a controller.
Background
Currently, an active noise reduction (ANC) technique applied to an earphone has two modes, which are called Feed-Forward noise reduction and Feedback noise reduction, respectively, and the combination of the Feed-Forward noise reduction and the Feedback noise reduction is called Hybrid noise reduction. Different active noise reduction techniques have their own limitations in noise reduction depth and bandwidth, which are mainly determined by the headphone acoustic structure, signal processing and system signal delay.
The working principle of the feedforward noise reduction system is mainly to output a signal with the same frequency response as the environmental noise but opposite phase to realize noise reduction. The reference microphone detects noise and generates an inverse signal through the filter circuit, and the inverse signal and the noise signal are offset at the eardrum, so that the noise level heard by human ears is reduced. The filter circuit is mainly used for compensating the difference between the noise detected at the ear drum and the microphone, and also has a compensation effect on the response capability of the loudspeaker in terms of the noise reduction signal.
The principle of operation of a feedback noise reduction system is primarily to detect noise in the eardrum region and then form a basic feedback loop to minimize the noise level in that region. The whole loop is composed of the responses of the loudspeaker and the microphone and the filter. As the filter gain (and its loop gain) increases, the noise residual becomes smaller, and thus the noise reduction performance is improved. However, if the phase of the loop is close to + -180 DEG, the "loop" "signal is inverted and the" + "" sign on the denominator is changed to "-". In this case, the loop gain size adjustment is limited because when it increases from 0.0 to 1.0, the result is amplification, and when it equals 1.0, the result is "zero division", easily causing system instability and often causing howling as the frequency response amplitude increases.
The Hybrid active anti-noise system (Hybrid ANC) combines the feedforward noise reduction system and the feedback noise reduction system, thereby effectively improving the respective defects of the feedforward noise reduction system and the feedback noise reduction system. Hybrid-type active anti-noise systems typically include a pair of microphones, and feedforward anti-noise systems use an external microphone to measure the ambient noise before entering the ear, process the signal to ensure an accurate inverted signal, and effectively cancel the ambient noise with the system's speakers. The filter of the feedback anti-noise system is used for collecting the acoustic signals near the error microphone and feeding back the acoustic signals to perform error correction. However, in the conventional hybrid active anti-noise architecture, when the noise is at a higher frequency and is regular, the feedback noise cancellation system is prone to generate an unstable condition, which results in a poor noise cancellation effect.
Disclosure of Invention
The objective of the present invention is to provide a weighted hybrid active anti-noise system, which includes a reference microphone, an error microphone, a speaker, and a controller connected to the reference microphone, the error microphone, and the speaker. The controller comprises a feedforward noise reduction filter module, a feedback noise reduction filter module, a mixer, a noise detection module and a weight distribution module, wherein the feedforward noise reduction filter module performs feedforward noise reduction on a reference signal received by the reference microphone to obtain a feedforward noise reduction signal, the feedback noise reduction filter module performs feedback noise reduction on an error sound source signal received by the error microphone to obtain a feedback noise reduction signal, the feedforward noise reduction signal and the feedback noise reduction signal are transmitted to the mixer to be mixed, and the mixed noise reduction signal is output to the loudspeaker, the weight distribution module comprises one or a plurality of weight modulation units arranged between the error microphone and the feedback noise reduction filter module, and when the noise detection module detects high-frequency noise by the reference microphone or the error microphone, a control signal is transmitted to the weight distribution module, the weight distribution module reduces the weight value of the weight modulation unit so as to reduce the proportion of the feedback signal of the feedback noise reduction filtering module.
Another objective of the present invention is to provide a controller, which includes a feedforward noise reduction filtering module, a feedback noise reduction filtering module, a mixer, a noise detection module, and a weight assignment module. The feedforward noise reduction filter module performs feedforward noise reduction on the reference signal received by the reference microphone to obtain a feedforward noise reduction signal. The feedback noise reduction filter module performs feedback noise reduction on the error sound source signal received by the error microphone to obtain a feedback noise reduction signal. The mixer mixes the feedforward noise reduction signal and the feedback noise reduction signal and outputs a noise reduction signal. The noise detection module detects high-frequency noise from the input of the feedforward noise reduction filtering module or the feedback noise reduction filtering module, and outputs a control signal when the high-frequency noise is detected. The weight distribution module comprises one or a plurality of weight modulation units arranged between the error microphone and the feedback noise reduction filter module, and when the control signal is received, the weight value of the weight modulation unit is reduced so as to reduce the proportion of the feedback signal of the feedback noise reduction filter module.
Therefore, the present invention has the following advantages over the prior art:
1. the invention adds a weight modulation function on the feedback path, and can properly reduce the weight on the feedback path when the performance is poor, so that the feedforward path is led to achieve the real self-adaptive effect.
2. The invention can strengthen the processing effect corresponding to the irregular noise and the regular noise so as to improve the defect that the traditional mixed active anti-noise framework is easy to generate instability when processing the high-frequency regular noise.
Drawings
FIG. 1 is a schematic diagram of a weighted mixed-mode active anti-noise system according to the present invention.
FIG. 2 is a schematic diagram of the weighted mixed-mode active anti-noise system according to the present invention (II).
FIG. 3 is a flowchart illustrating a control procedure of the weighted mixed-mode active anti-noise system according to the present invention.
FIG. 4 is a flowchart illustrating a control procedure of the weighted mixed-mode active anti-noise system according to the present invention.
100 weight type mixed type active anti-noise system; 10 reference microphone; 20 error microphones; 30 speakers; 31 a speaker unit; 32 a drive unit; 40 a controller; f1 feedforward noise reduction filter module; f11 secondary path filter; f12 adaptive operator; f13 digital filter; f2 feedback noise reduction filtering module; f21 secondary path filter; f22 adaptive operator; f23 digital filter; an F3 mixer; f4 noise detection module; f5 weight assignment module; an F5A weight modulation unit; f51 a first complementary weight modulator; f52 a second complementary weight modulator; f53 a first weight modulator; f54 second weight modulator; steps S01-S06
Detailed Description
The detailed description and technical contents of the present invention will be described below with reference to the accompanying drawings. Furthermore, for convenience of illustration, the drawings are not necessarily drawn to scale, and they are not intended to limit the scope of the invention.
Embodiments of the present invention may be implemented in a noise reduction device or noise reduction controller in a personal listening system including a wired headset, a smart phone handset, a wireless headset or other head-worn audio device, and are not limited in this disclosure. The controller described in the present invention may be formed by a single chip or a plurality of chips, and in another embodiment, the controller may be a chip provided in an audio device (e.g. a mobile device) or an audio chip integrated or separated from a wireless headset or a head-mounted device, which are not intended to limit the scope of the present invention. Specifically, the controller may be, for example, a Microprocessor (Microprocessor), a Digital Signal Processor (DSP), or other similar devices or combinations thereof, which are not limited in the present invention.
Referring to fig. 1, a schematic diagram (a) of the weighted hybrid active anti-noise system according to the present invention is shown, wherein:
the present embodiment discloses a weighted hybrid active anti-noise system 100, which mainly includes a reference microphone 10, an error microphone 20, a speaker 30, and a controller 40 connected to the reference microphone 10, the error microphone 20, and the speaker 30.
The reference Microphone 10 (fed Microphone) is mainly used for receiving a reference sound source signal. The reference audio signal is mainly the ambient noise, i.e. the noise that the anti-noise system mainly filters. The reference microphone 10 may be a microphone, a sound pickup, or other devices capable of receiving ambient sound waves and further converting the ambient sound waves into analog and digital audio in one embodiment.
The error Microphone 20(Feedback Microphone) is mainly used for receiving an error sound source signal. The error microphone 20 is generally disposed at a reference position within the anti-noise region, and the audio received by the error microphone 20 corresponds to the difference between the reference audio and the inverted signal output from the speaker 30, which is defined as an error source signal. Like the reference microphone 10, the error microphone 20 may be a microphone, a sound pickup, or other devices capable of receiving ambient sound waves and further converting the ambient sound waves into analog and digital audio in one embodiment.
The speaker 30 is mainly used to output a reverse signal to cancel the noise in the environment. The speaker 30 may be, for example, a headphone, a speaker or other such devices for outputting the reverse signal to cancel noise in one embodiment. The speaker 30 mainly includes a speaker unit 31 and a driving unit 32 connected to the speaker unit 31. The driving unit 32 is used to convert the received digital signal into an analog signal for the speaker unit 31 to output as sound.
The controller 40 is connected or coupled to the reference microphone 10, the error microphone 20, and the speaker 30 via specific pins for coordinating the operations of the devices and processing the transmitted signals. Specifically, the controller 40 mainly includes a feedforward noise reduction filter module F1, a feedback noise reduction filter module F2, a mixer F3, a noise detection module F4, and a weight distribution module F5, it should be noted that these functional modules may be integrated into a single controller, or may be cooperatively executed by a plurality of independent controllers (for example, by a single or a plurality of controllers executing respective functional blocks), and these equivalent variations are not intended to limit the scope of the present invention.
In circuit configuration, the feedforward noise reduction filter module F1 receives the reference signal of the reference microphone 10, and transmits the reference signal after feedforward noise reduction processing as a first input signal (feedforward noise reduction signal) to the mixer F3, the feedback noise reduction filter module F2 receives the error sound source signal of the error microphone 20, and transmits the error sound source signal after feedback noise reduction processing as a second input signal (feedback noise reduction signal) to the mixer F3, so as to mix the first input signal and the second input signal through the mixer F3 to obtain a noise reduction signal, and output the mixed noise reduction signal to the speaker 30.
The noise detection module F4 receives audio from the reference microphone 10 or the error microphone 20 and determines the noise status from the audio, and the noise detection module F4 can be, for example, a spectral noise detector, a temporal noise detector, an adaptive noise filter detector, and the like. The weight distribution module F5 includes one or more weight modulation units F5A disposed between the error microphone 20 and the feedback noise reduction filter module F2, and when the noise detection module F4 detects high frequency noise from the reference microphone 10 or the error microphone 20, the weight distribution module F5 sends a control signal to the weight distribution module F5, and after receiving the control signal, the weight distribution module F5 reduces the weight value of the weight modulation unit F5A to reduce the output weight of the feedback signal of the feedback noise reduction filter module F2.
The feedforward noise reduction filter module F1 and the feedback noise reduction filter module F2 are described in detail below with reference to an embodiment. Please refer to fig. 2, which is a schematic diagram (two) of the weighted hybrid active anti-noise system of the present invention, and is shown in the figure:
the feedforward noise reduction Filter Module F1 mainly includes a Secondary Path Filter F11(Secondary Path Filter), an adaptive operator F12(Adaptation Algorithm Module), and a Digital Filter F13(Digital Filter). The sub-path filter F11 is defined by a path that a designer converts into an error audio signal e (n) according to a noise reduction signal y (n) to correct and compensate an input digital signal, thereby obtaining a reference signal waveform. The adaptive operator F12 updates the Filter coefficients of the digital Filter F13 according to the reference audio signal and the error audio signal, and the adaptive operator F12 may be, for example, a least mean square Filter (LMS Filter), which is not limited in the present invention. The digital Filter F13 filters the reference signal of the reference microphone 10 according to the updated Filter coefficient to obtain a feedforward noise reduction signal, and transmits the feedforward noise reduction signal to the mixer F3, wherein the digital Filter F13 may be a finite impulse response Filter (FIR Filter) or a Biquad Filter (Biquad Filter) in a possible implementation manner, which is not limited in the present invention.
The digital filter F13 of the feedforward denoising filter module F1 is mainly used to estimate the error caused by unknown environmental factors (e.g., ear muffs), and both the unknown environmental factors and the digital filter F13 are configured to receive the same input signal x (n). The problem of the secondary path, the simulation filter signal and the transformation set of the error source signal passing through the path from the electrical signal to the acoustic signal can be solved by introducing the filtering FXLMS algorithm. During the electroacoustic conversion process, the error effect generated therebetween is minimized by delaying or changing the signal.
The feedback noise reduction filtering module F2 mainly includes a Secondary Path Filter F21, a self-adaptive operator F22(Secondary Path Filter), and a Digital Filter F23(Digital Filter). Like the feedforward denoising filter module F1, the secondary path filter F21 is defined by a path that a designer converts into an error source signal e (n) according to a denoising signal y (n) to correct and compensate an input digital signal. The adaptive Filter F22 of the feedback denoising Filter module F2 updates the Filter coefficients of the digital Filter F23 by mixing the error signal e (n), the result signal y (n-1) output from the previous denoising signal of the secondary path, and the error source signal e (n) with the input signal of the denoising signal-error source signal mixer F6, and the adaptive operator F22 may be, for example, a least mean square Filter (LMS Filter), which is not limited in the present invention. The digital Filter F23 filters the resulting signal y (n-1) and the mixed signal of the error source signal e (n) according to the updated Filter coefficients, and outputs a feedback noise reduction signal to the second input terminal of the mixer F3, wherein the digital Filter F23 may be a finite impulse response Filter (FIR Filter) or a Biquad Filter in one possible implementation, which is not limited in the present invention. A secondary path filter F7 is installed at the front end of the noise reduction signal-error audio signal mixer F6 to correct and compensate the input noise reduction signal.
In this embodiment, the weight distribution module F5 includes a first complementary weight modulator F51 disposed between the mixer F3 and the feedforward denoising filter module F1, a second complementary weight modulator F52 disposed between the mixer F3 and the feedback denoising filter module F2, a first weight modulator F53 disposed between the error microphone 20 and the adaptive filter F22 of the feedback denoising filter module F2, and a second weight modulator F54 disposed between the error microphone 20 and the denoising signal-error source signal mixer F6. The weights of the first complementary weight modulator F51 and the second complementary weight modulator F52 are summed to a constant value, such as 1. The weight modulator F51 can be, for example, uniform modulation, weighted modulation, dynamic detection modulation, etc., and modulates the weight of each weight modulator F51 through software or firmware stored in a controller (or storage unit) to determine the signal amplification ratio of the weight modulator F51.
In another possible implementation, a weight modulator (not shown) may be provided before the common node of the first weight modulator F53 and the second weight modulator F54, and the weight of the input signal of the feedback noise reduction filter module F2 is controlled by a single weight modulator, but the efficiency is lower than that of the previous implementation.
Referring to fig. 3, regarding the control logic of the weight assignment module F5, the control flow of the weighted hybrid active anti-noise system according to the present invention is shown as follows:
when the system is started, the noise detection module F4 continuously detects the reference audio signal of the reference microphone 10 (and/or the error audio signal of the error microphone 20) and detects whether a noise is received (step S01).
When detecting noise, the noise detection module F4 determines the type of the noise, whether the type of the noise is regular noise or irregular noise (step S02), and determines whether the type of the noise can be determined by a spectrum noise detector, a time domain noise detector, an adaptive noise filter detector, etc. to distinguish the type of the noise as regular noise or irregular noise.
When the detected noise is at a high frequency and has regularity, an unstable condition is easily generated on the path of the feedback noise reduction filtering module F2, so that the noise reduction effect is reduced. At this time, the noise detection module F4 sends a first control signal to the weight assignment module F5 to switch the weight assignment module F5 to the first operation mode (step S03). In the first operating mode, the weight distribution module F5 gradually reduces the weight of the second complementary weight modulator F52 according to timing priority and further reduces the weight of the first weight modulator F53 and the second weight modulator F54.
Specifically, the weight assignment module F5 sets the weight of the first weight modulator F53 to 1, the weight of the second weight modulator F54 to 1, and the weight of the second complementary weight modulator F52 to 0.5 at a start initial value.
When irregular noise is detected, the weight of the second complementary weight modulator F52 is adjusted to be smaller (minimum can be adjusted to 0) according to the time sequence, so that the noise cancellation effect of the whole system is biased to the feedforward noise reduction filtering module F1 to process the irregular noise.
Subsequently, the weight distribution module F5 further slowly adjusts the weight of the first weight modulator F53 to be small (minimum can be adjusted to 0), so that the update mechanism of the feedback noise reduction filter module F2 slowly approaches a state of little contribution.
Finally, the weight of the second weight modulator F54 is adjusted to be gradually decreased (the minimum can be adjusted to 0), so that the influence of the signal reconstructed by the final feedback denoising filter module F2 on the error (error) is minimized.
In the above process, the timing sequence is adjusted in advance by the design engineer, and the weight modulators are triggered in sequence through time. In another possible implementation aspect, the weight assignment module F5 can determine whether to continue modulating the weights according to the error rate of the noise detection module F4.
When the noise detection module F4 detects the loss of the irregular noise, the weight distribution module F5 directly or gradually returns the weight of each weight modulator to the initial value (the weight of the first weight modulator F53 is set to 1, the weight of the second weight modulator F54 is set to 1, and the weight of the second complementary weight modulator F52 is set to 0.5) (step S04).
In step S02, when the detected noise is regular, the noise detection module F4 sends a second control signal to the weight distribution module F5 to switch the weight distribution module F5 to the second operation mode (step S05). The weight assignment module F5 gradually increases the weight of the second complementary weight modulator F52 (adjusted to 1 at the highest) according to timing priority in the second operating mode.
Specifically, when the weight distribution module F5 is in the second operation mode, the weight distribution module F5 increases the weight of the second complementary weight modulator F52 (to 1 at most), so that the overall noise cancellation effect of the system is biased toward the path of the feedback noise reduction filter module F2 for processing the regular noise. Since the regular noise is processed by the feedback de-noising filter module F2, the first weight modulator F53 and the second weight modulator F54 are kept at the initial values
When the noise detection module F4 detects the loss of the regular noise, the weight distribution module F5 directly or gradually returns the weight of each weight modulator to the initial value (the weight of the first weight modulator F53 is set to 1, the weight of the second weight modulator F54 is set to 1, and the weight of the second complementary weight modulator F52 is set to 0.5) (step S06).
In summary, the present invention adds a weight modulation function to the feedback path, so that the weight can be properly reduced on the feedback path when the performance is deteriorated, and the feedforward path can be led to achieve the real adaptive effect. In addition, the invention can strengthen the processing effect corresponding to the irregular noise and the regular noise so as to improve the defect that the traditional mixed active anti-noise framework is easy to generate instability when processing the high-frequency regular noise.
Although the present invention has been described in detail, it should be understood that the above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the invention, i.e., the appended claims are intended to cover all such modifications and changes as fall within the true spirit and scope of the invention.
Claims (4)
1. A weighted mixed active anti-noise system is characterized by comprising
A reference microphone;
an error microphone;
a speaker; and
a controller connected to the reference microphone, the error microphone and the speaker, wherein the controller comprises a feedforward noise reduction filter module, a feedback noise reduction filter module, a mixer, a noise detection module and a weight distribution module, the feedforward noise reduction filter module performs feedforward noise reduction on a reference signal received by the reference microphone to obtain a feedforward noise reduction signal, the feedback noise reduction filter module performs feedback noise reduction on an error sound source signal received by the error microphone to obtain a feedback noise reduction signal, the feedforward noise reduction signal and the feedback noise reduction signal are transmitted to the mixer to be mixed, and the mixed noise reduction signal is output to the speaker, the weight distribution module comprises one or more weight modulation units arranged between the error microphone and the feedback noise reduction filter module, and the controller transmits control signals when the noise detection module detects high-frequency noise from the reference microphone or the error microphone The weight distribution module reduces the weight value of the weight modulation unit so as to reduce the proportion of the feedback noise reduction signal of the feedback noise reduction filtering module;
the weight distribution module comprises a first complementary weight modulator arranged between the mixer and the feedforward noise reduction filtering module and a second complementary weight modulator arranged between the mixer and the feedback noise reduction filtering module, and the weight sum of the first complementary weight modulator and the second complementary weight modulator is a constant value;
the weight distribution module comprises a first weight modulator arranged between the error microphone and the adaptive filter of the feedback noise reduction filtering module, and a second weight modulator arranged between the error microphone and the noise reduction signal-error sound source signal mixer;
the noise detection module transmits a first control signal to the weight distribution module when the noise detection module detects irregular high-frequency noise from the reference microphone or the error microphone, and the weight distribution module gradually reduces the weight of the second complementary weight modulator according to a time sequence or an error rate collected by the error microphone and sequentially reduces the weights of the first weight modulator and the second weight modulator when the weight distribution module receives the first control signal.
2. The weighted mixed-mode active anti-noise system of claim 1, wherein the noise detection module sends a second control signal to the weight distribution module when detecting regular high-frequency noise from the reference microphone or the error microphone, and the weight distribution module gradually increases the weight of the second complementary weight modulator according to timing priority when receiving the second control signal.
3. A controller, wherein the controller is disposed in a weighted hybrid active anti-noise system with a reference microphone and an error microphone, the controller comprising:
a feedforward noise reduction filter module, which performs feedforward noise reduction on the reference signal received by the reference microphone to obtain a feedforward noise reduction signal;
a feedback noise reduction filter module, which performs feedback noise reduction on the error sound source signal received by the error microphone to obtain a feedback noise reduction signal;
a mixer for mixing the feedforward noise reduction signal and the feedback noise reduction signal and outputting a noise reduction signal;
a noise detection module, which detects the high frequency noise from the input of the feedforward noise reduction filter module or the feedback noise reduction filter module and outputs a control signal when detecting the high frequency noise; and
a weight distribution module, which comprises one or more weight modulation units arranged between the error microphone and the feedback noise reduction filter module, and reduces the weight value of the weight modulation unit to reduce the proportion of the feedback noise reduction signal of the feedback noise reduction filter module when receiving the control signal;
the weight distribution module comprises a first complementary weight modulator arranged between the mixer and the feedforward noise reduction filtering module and a second complementary weight modulator arranged between the mixer and the feedback noise reduction filtering module, and the sum of the weights of the first complementary weight modulator and the second complementary weight modulator is a constant value;
the weight distribution module also comprises a first weight modulator at the front end of the LMS filter of the feedback noise reduction filtering module and a second weight modulator arranged at the front end of the noise reduction signal-error sound source signal mixer;
when the noise detection module detects irregular high-frequency noise from the reference microphone or the error microphone, a first control signal is transmitted to the weight distribution module, and when the weight distribution module receives the first control signal, the weight distribution module gradually reduces the weight of the second complementary weight modulator according to a time sequence or the error rate collected by the noise detection module, and sequentially reduces the weights of the first weight modulator and the second weight modulator.
4. The controller as claimed in claim 3, wherein the noise detection module sends a second control signal to the weight distribution module when the noise detection module detects regular high frequency noise from the reference microphone or the error microphone, and the weight distribution module gradually increases the weight of the second complementary weight modulator according to timing priority when the weight distribution module receives the second control signal.
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| CN112995855B (en) * | 2021-05-20 | 2021-08-13 | 成都爱旗科技有限公司 | Filter step length coefficient determining method and device and noise reduction device |
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