TW202207214A - Biquad error controling feedback type active noise cancellation system - Google Patents

Abstract

The present invention provides a biquad error controlling feedback type active noise cancellation system, which comprises an error voice receiving device, a voice outputting device, an error shaping device, and a feedback module. The error voice receiving device receives an error voice signal and outputs an error signal. The voice outputting device outputs a voice signal. The input of the error shaping device connects to the error voice receiving device to receive the error signal. After the error shaping device cancels the high-frequency noise of the error signal, the error shaping device outputs an error shaping signal. The input of the feedback module connects to the output of the error shaping device and receives the voice signal. The feedback module outputs a noise cancelled signal according to the error shaping signal and the voice signal.

Description

Feedback Active Anti-Noise System Based on Biquadratic Error Control

The present invention provides a feedback-type active anti-noise system, in particular to a feedback-type active anti-noise system capable of improving the noise reduction effect with biquadical error control.

Active Noise Control (ANC) is a device that can block specified noises while leaving other sounds unaffected. The main principle is to accept the specified noise according to the sound source receiving device, and use the sound transmitting device to send out sound waves with completely opposite phases, so that the two sound waves can cancel each other, so as to filter the noise. At present, active anti-noise technology has been widely used in sound-isolating speakers and noise-cancelling headphones of aircraft and fighters.

The traditional feedback active anti-noise technology mainly uses a filter (FIR filter) to convert the received error signal into a corresponding reverse signal, thereby filtering out noise. However, the high frequency of the input error signal may cause the adaptive operation at the front end of the filter (FIR filter) to diverge, resulting in poor noise reduction.

The main purpose of the present invention is to provide a feedback active anti-noise system with biquad error control, including an error receiving device, an audio output device, an error shaper, and a feedback module. The error receiving device receives an error source signal and outputs an error signal. The audio output device outputs an audio signal. The input terminal of the error shaper is connected to the error receiving device to receive the error signal. The error shaper includes a noise bandwidth detector, and an input terminal is connected to the coefficient correction of the noise bandwidth detector. a 1- to N-order biquad filter whose input end is connected to the coefficient modifier, the noise bandwidth detector calculates the bandwidth of the error signal, and the coefficient modifier modifies the error signal according to the bandwidth coefficients of the 1- to N-order biquad filters, the 1- to N-order biquad filters remove high-frequency noise of the error signal of the next sample according to the modified coefficients and output an error integer signal. The input end of the feedback module is connected to the output end of the error shaper to receive the audio signal, the output end of the feedback module is connected to the audio output device, the feedback module includes a mixer, and an input end is connected to the audio output device. An LMS operator with an error shaper output and an output of the mixer, and an adaptive filter with an input connected to the output of the LMS operator and the output of the mixer, the input of the mixer connected to the error shaper The output terminal receives the audio signal, the mixer mixes the error-shaped signal and the audio signal and outputs a mixed signal, and the LMS operator updates the adaptive signal according to the received error-shaped signal and the mixed signal The weight coefficient of the filter, the adaptive filter filters the mixed signal according to the updated weight coefficient and outputs a noise reduction signal to the audio output device.

Therefore, compared with the prior art, the present invention can reduce the high-frequency noise of the error signal, and can adjust and eliminate the high-frequency noise according to the requirements, and further avoid the operation divergence of the adaptive filter, which leads to the reduction of the noise reduction effect. .

The detailed description and technical content of the present invention are described below with reference to the drawings. Furthermore, the drawings in the present invention are not necessarily drawn according to the actual scale for the convenience of description. These drawings and their scales are not intended to limit the scope of the present invention, and are described here in advance.

In one embodiment, the present invention can be implemented as a noise reduction device or noise reduction controller in a personal listening system including wired headsets, smart phones, wireless headsets, or other head-worn audio devices. is not restricted.

The "devices", "devices", "modules" and their corresponding functions described in the present invention may be performed by a single chip or a combination of a plurality of chips, and the number of these chip configurations is not within the scope of the present invention. the range to be limited. In addition, the chip can be but not limited to a processor (Processor), a central processing unit (CPU), a microprocessor (Microprocessor), a digital signal processor (Digital Signal Processor, DSP), special applications The combination of integrated circuits (Application Specific Integrated Circuits, ASIC), programmable logic devices (Programmable Logic Device, PLD) and other devices is not limited in the present invention. In another embodiment of the present invention, the "device", "device", "module" or a combination thereof may be a chip provided by an audio device (such as a mobile device or a wearable device), or may be integrated or separated into a wired headset , wireless earphones, or audio chips of head-mounted devices, and these changes are not intended to be limited by the present invention.

One of the embodiments of the present invention will be described below. Please refer to FIG. 1 , which is a block diagram of the feedback active anti-noise system for biquad error control according to the present invention, as shown in the figure:

Referring to FIG. 1 , the present embodiment discloses a feedback active anti-noise system 100 with biquad error control, which mainly includes an error receiving device 10 , an audio output device 20 , an error shaper 30 , and a feedback module 40 .

The error receiving device 10 is mainly used to receive the error audio source signal. The error receiving device 10 is generally arranged between the speaker and the human ear. The audio signal received by the error receiving device 10 mainly includes noise NS and speakers. The difference between the output sounds is defined here as the error sound source signal. In one embodiment, the error receiving device 10 can be, for example, a microphone, a microphone, or other devices that can receive ambient sound waves and further convert them into analog and digital audio. In one embodiment, the error receiving device 10 includes an error microphone 12 , a preamplifier 14 connected to the back end of the error microphone 12 , an anti-aliasing filter 16 connected to the back end of the preamplifier 14 , and An analog-to-digital converter 18 is connected to the rear end of the anti-aliasing filter 16 . Finally, the analog-to-digital converter 18 outputs the error signal to the error shaper 30 .

The audio output device 20 is mainly used for outputting the noise reduction signal and the original audio for canceling the noise NS. In one embodiment, the audio output device 20 can be, for example, a speaker, a speaker, and a corresponding audio processing chip, and other devices for outputting sound. Here, the output sound is defined as an audio signal. In one embodiment, the audio output device 20 sequentially includes a speaker 28, a power amplifier 26 connected to the front end of the speaker 28, a reconstruction filter 24 connected to the front end of the power amplifier 26, and a reconstruction filter 24 connected to the front end of the speaker 28. Digital-to-analog converter 22 in front of filter 24. Wherein, the digital-to-analog converter 22 receives the noise reduction signal of the feedback module 40 and the original audio signal (the input position is not shown in the figure), and the aforesaid original audio signal is music, human voice or other sound that has not yet entered the space and is not affected by the noise NS, Not limited in the present invention.

The error shaper 30 is mainly used for reducing the high frequency noise of the error signal, and the error signal after reducing the high frequency noise is defined as an error shaping signal. Please refer to "FIG. 2", "FIG. 3", and "FIG. 4" together, which are a block diagram of the error shaper 30, a block diagram of a biquad filter, and a hierarchical configuration of a 1st to Nth order biquad filter in the present invention, as the picture shows:

The input end of the error shaper 30 is connected to the output end of the error receiving device 10 to receive the error signal. In one embodiment, the error shaper 30 sequentially includes a noise bandwidth detector 32, a coefficient modifier 34 whose input terminal is connected to the noise bandwidth detector 32, and an input terminal connected to the noise bandwidth detector 32. 1st to Nth order biquad filter 36 of coefficient modifier 34 . The input terminal of the noise bandwidth detector 32 is connected to the output terminal of the error receiving device 10 ; the other input terminal of the coefficient corrector 34 is connected to the error microphone 12 , and the coefficient corrector 34 and the error microphone 12 are connected to the other input terminal of the coefficient corrector 34 . A Frequency Detector (not shown) is arranged therebetween; the input ends of the respective biquad filters in the 1st to Nth order biquad filters 36 are connected to the coefficient modifier 34. Specifically, the The other input terminal of the 1st-order biquad filter 361 of the 1st to Nth-order biquad filters 36 is connected to the error receiving device 10 . Finally, the N-order biquad filter 36N of the 1 to N-order biquad filters 36 outputs the error-shaped signal to the feedback module 40 .

The hierarchical configuration of the aforementioned 1st to Nth order biquad filters 36 is as follows, please refer to “FIG. 4”: the output end of the 1st order biquad filter 361 is connected to the other input end of the 2nd order biquad filter 362; The output terminal of the biquad filter 362 is connected to the other input terminal of the 3rd order biquad filter 363, and so on, the output terminal of the N-1 order biquad filter 36N-1 is connected to the N order biquad filter 36N the other input.

The input end of the feedback module 40 is connected to the error shaper 30 and receives the audio signal, so as to perform an adaptive operation on the received audio signal and the error-shaping signal, and use the generated inverse signal to counteract the noise. The pin is used to achieve the noise reduction effect, and the signal output by the feedback module 40 for canceling the noise NS is defined as the noise reduction signal. In one embodiment, please also refer to FIG. 5 , the feedback module 40 includes a mixer 42 , an LMS operator 44 (Least Mean Square Filter) whose input terminal is connected to the output terminal of the mixer 42 , and an input terminal connected to the output terminal of the mixer 42 . An adaptive filter 46 (Adaptive filter) of the LMS operator 44 . The other input end of the LMS operator 42 is connected to the output end of the error shaper 30; the other input end of the adaptive filter 46 is connected to the mixer 42, and the output end of the adaptive filter 44 is connected to the audio output device 20. In this embodiment, the signal input to the speaker 38 has a first secondary path filter 41 between the paths fed back to the mixer 42 to filter the audio signal in advance; the output end of the mixer 42 There is a second secondary path filter 43 between the path to the input 44 of the LMS operator to filter the mixed signal in advance. The first secondary path filter 41, the second secondary path filter 43 and the path filter 43 are used as transfer functions for estimating the actual path, so that the LMS operator 44 can adjust the coefficients of the adaptive filter 46 to generate the same size as the noise NS, The noise reduction signal with opposite phase is sent to the audio output device 20 .

The above describes a specific embodiment of the hardware structure of the present invention, and the operation of the present invention will be further described below. Please refer to "Fig. 3", "Fig. 4", "Fig. Figure 6" is a schematic diagram of the control logic and flow chart of the biquad filter, the hierarchical configuration of the 1- to N-order biquad filter, and the feedback active anti-noise system controlled by the biquad error amount according to the present invention, as shown in the figure. :

First, the noise NS and the audio signal are received by the error microphone 12 of the error receiving device 10, and the noise NS and the audio signal are converted into an error signal of digital audio through the error receiving device 10 to the error shaper 30 (step S201). When the system is activated, the audio signal has not undergone noise reduction processing, and the audio signal at this time is the original audio.

其中，

為n階段由該誤差收訊裝置10輸入的誤差訊號，

為該雜訊頻寬偵測器32輸出的該中心頻率，

共有M個輸出，M為預設的輸出數量。The noise bandwidth sensor 32 of the error shaper 30 detects the bandwidth of the error signal and outputs a noise bandwidth signal with the same bandwidth as the center frequency of the error signal to the coefficient modifier 34 (step S202 ). The center frequency is obtained by the noise bandwidth detector 32 through the error signal according to the following formula:

in,

is the error signal input by the error receiving device 10 in n stages,

is the center frequency output by the noise bandwidth detector 32,

There are M outputs in total, where M is the preset number of outputs.

其中，

為中心角頻率數值，

為固有頻率參數，

、

、

、

、

為各別雙二階濾波器361-36N的係數。The coefficient modifier 34 receives the error microphone signal and the noise bandwidth signal, and calculates a coefficient correction signal for adjusting the coefficients of the biquad filter to the 1st to Nth order biquad filter 36, so that the 1st to Nth order biquad filter 36. Correct the coefficient according to the bandwidth of the error signal (step S203). In other words, the coefficients of the 1st to Nth order biquad filters 36 of the present invention can be modified by the coefficient modifier 34 to adjust the high frequency noise to be modified. Referring to FIG. 3, the coefficient modifier 34 modifies the coefficients of the respective biquad filters 361-36N according to the following equation:

in,

is the center angular frequency value,

is the natural frequency parameter,

,

,

,

,

are the coefficients of the respective biquad filters 361-36N.

以及該固有頻率參數

由該係數修正器34依據下列的式子獲得：

其中，

為由該雜訊頻寬偵測器32輸入的中心頻率，

為由該誤差麥克風12輸入的誤差麥克風訊號的頻率，Q為預設的品質參數，

為中心角頻率數值，

為固有頻率參數。前述提及的品質參數Q基於品質因素而決定；固有頻率參數

基於固有頻率因子而決定。The aforementioned center angular frequency value

and the natural frequency parameter

It is obtained by the coefficient modifier 34 according to the following formula:

in,

is the center frequency input by the noise bandwidth detector 32,

is the frequency of the error microphone signal input by the error microphone 12, Q is a preset quality parameter,

is the center angular frequency value,

is the natural frequency parameter. The aforementioned quality parameter Q is determined based on the quality factor; the natural frequency parameter

Determined based on the natural frequency factor.

、

視為已知參數)，由該N階雙二階濾波器36N輸出一錯誤整形訊號（步驟S204）。所述的各別雙二階濾波器361-36N係依據下列的式子對該誤差訊號進行濾波：

； 其中，

、

、

係為第

階、第

階、及第

階時點所接收到的誤差訊號，

、

、

係為第

階、第

階、及第

階時點輸出的該錯誤整型訊號，

、

、

、

、

係為各別雙二階濾波器361-36N的係數。Then, the 1st to Nth order biquad filters 36 correct the coefficient according to the bandwidth of the received error signal, and eliminate the high frequency noise of the next sampled error signal according to the corrected coefficient (

,

regarded as a known parameter), an error-shaped signal is output from the N-order biquad filter 36N (step S204). The respective biquad filters 361-36N filter the error signal according to the following equation:

; in,

,

,

the first

step, first

order, and

The error signal received at the order time point,

,

,

the first

step, first

order, and

The erroneous integer signal output at the time point of the step,

,

,

,

,

are the coefficients of the respective biquad filters 361-36N.

Next, the audio signal and the error-shaping signal that have passed through the first secondary filter 41 are mixed by the mixer 42 of the feedback module 40 to output a mixed signal (step S205 ).

The LMS operator 44 receives the error-shaping signal and the mixed signal through the second secondary path filter 43 to update the weights of the adaptive filter 46, so that the adaptive filter 46 adjusts the received mixed signal to be the same as the noise NS , the noise reduction signal with opposite phase, the adaptive filter 46 outputs the noise reduction signal to the audio output device 20 (step S206 ).

Finally, the audio output device 20 uses the received noise reduction signal to eliminate the next-order noise NS, and converts the noise reduction signal and the original audio to output an analog audio signal (step S207 ). In other words, the audio signal achieves the noise reduction effect by the noise reduction signal of the previous stage, so that the original audio in the audio signal is not affected by the noise NS and enters the human ear.

To sum up, compared with the prior art, the present invention can reduce the high-frequency noise of the error signal, and can adjust the high-frequency noise to be eliminated according to the requirements, and further avoid the adaptive filter. The operation diverges and the noise reduction effect is reduced.

The present invention has been described in detail above, however, the above-mentioned is only a preferred embodiment of the present invention, and should not limit the scope of the present invention by this Equivalent changes and modifications should still fall within the scope of the patent of the present invention.

100: Feedback active anti-noise system for biquad error control 10: Error receiving device 12: Error Microphone 14: Preamplifier 16: Anti-aliasing filter 18: Analog-to-Digital Converter 20: Audio output device 22: Digital-to-Analog Converter 24: Reconstruction filter 26: Power Amplifier 28: Speakers 30: Bad Integer 32: Noise Bandwidth Detector 34: Coefficient Corrector 36:1 to Nth order biquad filter 361-36N: Biquad Filters 40: Feedback Module 41: First secondary path filter 42: Mixer 43: Second Secondary Path Filter 44: LMS Calculator 46: Adaptive Filter NS: noise S201-207: Steps

FIG. 1 is a block diagram of a feedback active anti-noise system with biquad error control according to the present invention.

FIG. 2 is a block diagram of an error shaper of the present invention.

FIG. 3 is a block diagram of a biquad filter according to the present invention.

FIG. 4 is a block diagram illustrating the hierarchical configuration of 1st to Nth order biquad filters according to the present invention.

FIG. 5 is a schematic diagram of the control logic of the feedback active anti-noise system for biquad error control according to the present invention.

FIG. 6 is a schematic flow chart of the feedback active anti-noise system for biquad error control according to the present invention.

10: Error receiving device

20: Audio output device

30: Bad Integer

40: Feedback Module

41: First secondary filter

42: Mixer

43: Second Secondary Filter

44: LMS Calculator

46: Adaptive Filter

NS: noise

Claims (10)

A feedback active anti-noise system with biquadical error control, comprising: an error receiving device, receiving an error source signal and outputting an error signal; an audio output device, outputting an audio signal; an error shaper, the input terminal of which is connected to the error receiving device to receive the error signal, the error shaper includes a noise bandwidth detector, and an input terminal is connected to the coefficient of the noise bandwidth detector A modifier, and a biquad filter whose input end is connected to the coefficient modifier, the noise bandwidth detector calculates the bandwidth of the error signal, and the coefficient modifier is based on the bandwidth of the error signal modifying the coefficients of the 1st to Nth order biquad filters, the 1st to Nth order biquad filters remove high-frequency noise of the error signal of the next sample according to the modified coefficients and output an error integer signal; and A feedback module, the input end of which is connected to the output end of the error shaper and receives the audio signal, the output end of the feedback module is connected to the audio output device, the feedback module includes a mixer, an input end connected to an LMS operator to the output of the error shaper and the output of the mixer, and an adaptive filter with an input connected to the output of the LMS operator and the output of the mixer, the input of the mixer connected to the The output end of the error shaper receives the audio signal, the mixer mixes the error shaper signal and the audio signal and outputs a mixed signal, and the LMS operator updates according to the received error shaper signal and the mixed signal weight coefficient of the adaptive filter, the adaptive filter filters the mixed signal according to the updated weight coefficient and outputs a noise reduction signal to the audio output device. The feedback-type active anti-noise system for biquad-order error control as described in claim 1, wherein the error receiving device comprises an error microphone, a preamplifier connected to the rear end of the error microphone, a connection An anti-aliasing filter at the back end of the preamplifier, and an analog-to-digital converter connected to the back end of the anti-aliasing filter. The feedback active anti-noise system with biquad-order error control as described in claim 1, wherein the audio output device comprises a speaker, a power amplifier connected to the front end of the speaker, and a power amplifier connected to the speaker A front-end reconstruction filter, and a digital-to-analog converter connected to the front-end of the reconstruction filter. The feedback-type active anti-noise system with biquad-order error control as described in claim 2, wherein the input end of the noise bandwidth detector is connected to the error receiving device to detect the error signal bandwidth and output a noise bandwidth signal with the same bandwidth as the center frequency of the error signal; The input end of the coefficient corrector is connected to the error microphone to receive an error microphone signal, and according to the error microphone signal and the noise bandwidth signal, a coefficient correction signal for adjusting the coefficients of the biquad filter is output to the 1st to Nth order biquad filters; The input end of the 1st-order biquad filter is connected to the error receiving device to receive the error signal, the 1st to Nth-order biquad filters update the coefficient according to the coefficient correction signal and correct the next sampled according to the coefficient After the error signal, the error integer signal is output by the N-order biquad filter. The feedback active anti-noise system for biquad error control as described in item 4 of the claimed scope, wherein the respective biquad filters filter the error signal according to the following formula:

; in,

,

,

the first

step, first

order, and

The error signal received at the order time point,

,

,

the first

step, first

order, and

The erroneous integer signal output at the time point of the step,

,

,

,

,

are the coefficients of the respective biquad filter. The feedback-type active anti-noise system for biquad error control according to claim 5, wherein the coefficient modifier modifies the coefficients of the respective biquad filters according to the following formula:

in,

is the center angular frequency value,

is the natural frequency parameter,

,

,

,

,

are the coefficients of the respective biquad filter. The feedback-type active anti-noise system with biquad-order error control as described in claim 6, wherein the central angular frequency value and the natural frequency parameter are obtained by the coefficient modifier according to the following formula:

in,

is the center frequency input by the noise bandwidth detector,

is the frequency input by the error microphone, Q is the preset quality parameter,

is the center angular frequency value,

is the natural frequency parameter. For the feedback active anti-noise system with biquad error control in claim 7, the center frequency is obtained by the noise bandwidth detector through the error signal according to the following formula:

in,

is the error signal input by the error receiving device in n stages,

is the center frequency of the noise bandwidth detector output,

There are M outputs in total, where M is the preset number of outputs. The feedback active anti-noise system with biquad error control according to claim 7, wherein the quality parameter is determined based on a quality factor, and the natural frequency parameter is determined based on the natural frequency factor. The feedback active anti-noise system with biquad error control as described in claim 1, wherein a first secondary path filter is provided between the path between the output end of the audio output device and the input end of the mixer There is a second secondary path filter between the path of the output end of the mixer and the input end of the LMS operator.

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