Double second-order error quantity integer active noise cancellation system

Abstract

This application belongs to the technical field of signal noise reduction, and provides a dual second-order error quantization active noise cancellation system, which includes a reference receiving device, an error receiving device, an audio output device, an error shaper, and a processor. The reference receiving device receives a reference sound source signal and outputs a reference signal. The error receiving device receives an error sound source signal and outputs an error signal. The audio output device outputs an audio signal. The input end of the error shaper is connected to the error receiving device to receive the error signal, and the error shaper eliminates the high-frequency noise of the error signal and outputs an error shaping signal. The input end of the processor is connected to the reference receiving device and the error shaper, and the processor reduces the noise of the error quantization signal and outputs a noise reduction signal to the audio output device. This application can reduce the high-frequency noise of the error signal, and can adjust according to requirements to eliminate the high-frequency noise. In addition, it can further avoid the problem that the operation of the adaptive filter diverges, resulting in a reduction in the noise reduction effect.

Description

[0001] This application claims the priority of a Taiwan, China patent with the invention title "Dual Second-Order Error Quantity Integer Active Noise Cancellation System" and the patent number 109127404, the entire content of which is incorporated herein by reference. Technical Field

[0002] This application belongs to the technical field of signal noise reduction, and provides a dual second-order error quantity integer active noise cancellation system, in particular to a dual second-order error quantity integer active noise cancellation system that can improve the noise cancellation effect. Background Art

[0003] Active Noise Control (ANC) is a device that can isolate specified noise while other sounds remain unaffected. The main principle is to receive the specified noise by a sound source receiving device and send out sound waves with completely opposite phases by a sound sending device, so that the two sound waves can cancel each other out, thereby filtering out the noise. Currently, active noise control technology has been widely applied to sound insulation speakers and noise reduction headphones on airplanes and fighter jets.

[0004] Traditional feedforward active noise control technology mainly uses a filter (FIR filter) to convert the received error signal into a corresponding reverse signal to filter 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 cancellation effect. Summary of the Invention

[0005] To solve the above problems, this application provides a dual second-order error quantity integer active noise cancellation system, including: a reference receiving device, an error receiving device, an audio output device, an error shaper, and a processor.

[0006] The reference receiving device receives a reference sound source signal and outputs a reference signal.

[0007] The error receiving device receives an error sound source signal and outputs an error signal.

[0008] The audio output device outputs an audio signal.

[0009] The input end of the error shaper is connected to the error signal receiving device to receive the error signal. The error shaper includes a noise bandwidth detector, a coefficient corrector with its input end connected to the noise bandwidth detector, and a 1st to Nth order biquadratic filter with its input end connected to the coefficient corrector. The noise bandwidth detector calculates the bandwidth of the error signal. The coefficient corrector corrects the coefficients of the 1st to Nth order biquadratic filter according to the bandwidth of the error signal. The 1st to Nth order biquadratic filter eliminates the high-frequency noise of the error signal of the next sample according to the corrected coefficients and outputs an error shaping signal from the 1st to Nth order biquadratic filter. The input end of the processor is connected to the reference signal receiving device and the error shaper. The output end of the processor is connected to the audio output device. The processor includes an LMS operator and an adaptive filter with its input end connected to the LMS operator. The LMS operator updates the coefficients of the adaptive filter according to the received reference signal and the error shaping signal. The adaptive filter outputs a noise reduction signal to the audio output device according to the updated coefficients.

[0010] Compared with the prior art, the present application can reduce the high-frequency noise of the error signal, and can adjust to eliminate the high-frequency noise according to requirements. Furthermore, it can further avoid the problem that the operation of the adaptive filter diverges, resulting in a reduction in the noise reduction effect. Description of the Drawings

[0011] Figure 1 It is a schematic diagram of the modules of the biquadratic error amount shaping active noise cancellation system of the present application.

[0012] Figure 2 It is a schematic diagram of the modules of the error shaper of the present application.

[0013] Figure 3 It is a schematic diagram of the modules of the biquadratic filter of the present application.

[0014] Figure 4 It is a schematic diagram of the module configuration of the 1st to Nth order biquadratic filter of the present application.

[0015] Figure 5 It is a schematic diagram of the control logic of the biquadratic error amount shaping active noise cancellation system of the present application.

[0016] Figure 6 It is a schematic diagram of the implementation process of the biquadratic error amount shaping active noise cancellation system of the present application.

[0017] 100: Dual second-order error quantity integer active noise cancellation system; 10: Reference receiving device; 12: Reference microphone; 14: Preamplifier; 16: Anti-aliasing filter; 18: Analog-to-digital converter; 20: Error receiving device; 22: Error microphone; 24: Preamplifier; 26: Anti-aliasing filter; 28: Analog-to-digital converter; 30: Audio output device; 32 Digital-to-analog converter; 34 Reconstruction filter; 36: Power amplifier; 38: Speaker; 40: Error integerizer; 42: Noise bandwidth detector; 44: Coefficient corrector; 46: 1st to Nth order dual second-order filter; 461 - 46N: Dual second-order filter; 50: Processor; 52: LMS calculator; 54: Adaptive filter; 56: Secondary filter; 60: Main path. Detailed implementation manner

[0018] Regarding the detailed description and technical content of this application, it is described as follows in conjunction with the drawings. And for the convenience of explanation, the scale of the drawings in this application may not be drawn according to the actual scale, and these drawings and their scales are not used to limit the scope of this application, which is hereby stated in advance.

[0019] This application can be implemented in a noise reduction device or a noise reduction controller of a personal listening system including a wired headset, a smart phone, a wireless headset, or other head-mounted audio devices, and this application does not limit this.

[0020] In this application, the described devices, apparatuses, and their corresponding functions can be cooperatively executed by a single chip or a combination of multiple chips, and the number of these chip configurations is not within the scope intended to be limited by this application. In addition, the chip can be, but is not limited to, a combination of devices such as a processor, a central processing unit (CPU), a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a programmable logic device (PLD), etc., which is not limited in this application. In another embodiment of this application, the device, apparatus, or their combination can be a chip provided by an audio device (such as a mobile device, a wearable device), or an audio chip integrated or separated in a wired headset, a wireless headset, or a head-mounted device, and these variations are not within the scope intended to be limited by this application.

[0021] The following describes one embodiment of this application. Please refer to Figure 1, which is a schematic diagram of the dual second-order error quantization active noise cancellation system of the present application, as shown in the figure:

[0022] Please refer to Figure 1 , the dual second-order error quantization active noise cancellation system 100 provided in this embodiment mainly includes a reference signal receiving device 10, an error signal receiving device 20, an audio output device 30, an error shaper 40, and a processor 50.

[0023] The reference signal receiving device 10 is mainly used to receive a reference sound source signal, and the reference sound source signal mainly includes ambient noise NS. In one embodiment, the reference signal receiving device 10 can be a microphone, a pickup, or other devices that can be used to receive ambient sound waves and further convert them into analog or digital audio. In one embodiment, the reference signal receiving device 10 sequentially includes a reference microphone 12, a preamplifier 14 connected to the rear end of the reference microphone 12, an anti-aliasing filter 16 connected to the rear end of the preamplifier 14, and an analog-to-digital converter 18 connected to the rear end of the anti-aliasing filter 16. Finally, the analog-to-digital converter 18 outputs a reference signal to the processor 50.

[0024] The error signal receiving device 20 is mainly used to receive an error sound source signal. The error signal receiving device 20 is generally arranged at a position within the noise cancellation area. The sound source signal received by the error signal receiving device 20 is equivalent to the difference between the reference sound source signal and the reverse signal output by the speaker, which is defined as the error sound source signal here. In one embodiment, the error signal receiving device 20 can be, for example, a microphone, a pickup, or other devices that can be used to receive ambient sound waves and further convert them into analog or digital audio. In one embodiment, the error signal receiving device 20 includes an error microphone 22, a preamplifier 24 connected to the rear end of the error microphone 22, an anti-aliasing filter 26 connected to the rear end of the preamplifier 24, and an analog-to-digital converter 28 connected to the rear end of the anti-aliasing filter 26. Finally, the analog-to-digital converter 28 outputs an error signal to the error shaper 40.

[0025] The audio output device 30 is mainly used to output a reverse signal to cancel the ambient noise NS in the environment. In one embodiment, the audio output device 30 can be a speaker, a horn, or other similar devices used to output a reverse signal to cancel sound waves. Here, the aforementioned reverse signal is defined as an audio signal. In one embodiment, the audio output device 30 sequentially includes a speaker 38, a power amplifier 36 connected to the front end of the speaker 38, a reconstruction filter 34 connected to the front end of the power amplifier 36, and a digital-to-analog converter 32 connected to the front end of the reconstruction filter 34. Among them, the digital-to-analog converter 32 receives the noise reduction signal from the processor 50.

[0026] The error shaper 40 mainly serves to reduce the high-frequency noise of the error signal, and defines the error signal after reducing the high-frequency noise as the error shaping signal. Please refer to Figure 2 , Figure 3 , Figure 4 , which are the block diagrams of the error shaper 40, the biquadratic filter, and the block diagram of the hierarchical configuration of the 1st to Nth order biquadratic filters in this application, as shown in the figure:

[0027] The input end of the error shaper 40 is connected to the error receiving device 20 to receive the error signal. In an embodiment, the error shaper 40 sequentially includes a noise bandwidth detector 42, a coefficient corrector 44 with its input end connected to the noise bandwidth detector 42, and a 1st to Nth order biquadratic filter 46 with its input end connected to the coefficient corrector 44. Among them, the input end of the noise bandwidth detector 42 is connected to the output end of the error receiving device 20; the other input end of the coefficient corrector 44 is connected to the reference microphone 12, and a frequency detector (not shown in the figure) is provided between the coefficient corrector 44 and the reference microphone 12; the other input end of the 1st order biquadratic filter 461 of the 1st to Nth order biquadratic filter 46 is connected to the error receiving device 20. Finally, the error shaping signal is output from the Nth order biquadratic filter 46N of the 1st to Nth order biquadratic filter 46 to the processor 50 (the structure of the biquadratic filter in the aforementioned 1st to Nth order biquadratic filter 46 is as Figure 3 shown).

[0028] The hierarchical configuration of the aforementioned 1st to Nth order biquadratic filter 46 is as follows, please refer to Figure 4 : The output end of the 1st order biquadratic filter 461 is connected to the other input end of the 2nd order biquadratic filter 462; the output end of the 2nd order biquadratic filter 462 is connected to the other input end of the 3rd order biquadratic filter 463, and so on, the output end of the (N - 1)th order biquadratic filter 46N - 1 is connected to the other input end of the Nth order biquadratic filter 46N.

[0029] One of the input ends of the processor 50 is connected to the reference receiving device 10, and the other input end is connected to the error shaper 40, which is used to perform an adaptive operation on the received reference signal and the error shaping signal to achieve a noise reduction effect. Here, the signal output by the processor 50 for canceling the environmental noise NS is defined as the noise reduction signal. Please refer to Figure 5, in one embodiment, the processor 50 includes an LMS arithmetic unit 52 and an adaptive filter 54 whose input terminal is connected to the LMS arithmetic unit 52. Among them, the input terminal of the LMS arithmetic unit 52 is connected to the error shaper 40, and another input terminal of the LMS arithmetic unit 52 is connected to the reference receiving device 10; another input terminal of the adaptive filter 54 is connected to the reference receiving device 10, and the output terminal of the adaptive filter 54 is connected to the audio output device 30. In this embodiment, a secondary path filter 56 is provided between the reference receiving device 10 and the LMS arithmetic unit 52 to pre-filter the reference signal in advance. The secondary path filter 56 serves as the transfer function for estimating the actual path, enabling the LMS arithmetic unit 52 to adjust the coefficients of the adaptive filter 54 to generate a noise reduction signal with the same magnitude and opposite phase as the environmental noise NS to the audio output device 30.

[0030] The above describes a specific embodiment of the hardware architecture of the present application. The operation of the present application will be further described below. Please refer to Figure 3 , Figure 4 , Figure 5 , Figure 6 , which are the block diagrams of the biquadratic filter, the hierarchical configuration of the 1st to Nth order biquadratic filters, the control logic schematic diagram, and the flow schematic diagram of the biquadratic error amount shaping active noise cancellation system of the present application, as shown in the figure:

[0031] First, the environmental noise NS is received by the reference microphone 12 of the reference receiving device 10, and the reference receiving device 10 converts the environmental noise NS into a digital audio reference signal; the environmental noise NS received by the reference microphone 12 is transmitted to the error receiving device 20 through the main path 60 (step S201). Among them, the main path 60 is the transmission path between the reference receiving device 10 and the error receiving device 20.

[0032] The error receiving device 20 receives the error sound source signal and converts the error sound source signal into a digital audio error signal to the error shaper 40 (step S202). Among them, the error sound source signal is the difference between the reference signal and the audio signal output by the audio output device 30.

[0033] The noise bandwidth sensor 42 of the error shaper 40 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 corrector 44 (step S203). The center frequency is obtained from the error signal by the noise bandwidth detector 42 according to the following formula:

[0034]

[0035] Among them, x[n] is the error signal input by the error receiving device 20 at the nth stage, f kis the center frequency output by the noise bandwidth detector 42, f k There are M outputs in total, and M is the preset number of outputs.

[0036] The coefficient corrector 44 receives the reference microphone signal and the noise bandwidth signal, and calculates a coefficient correction signal for adjusting the coefficients of the biquadratic filters to the biquadratic filters 46 of order 1 to N, so that the biquadratic filters 46 of order 1 to N correct the coefficients according to the bandwidth of the error signal (step S204). In other words, the coefficients of the biquadratic filters 46 of order 1 to N in the present application can be corrected by the coefficient corrector 44 to adjust the high-frequency noise to be corrected. Please refer to Figure 3 The coefficient corrector 44 corrects the coefficients of the biquadratic filters 461-46N according to the following formula:

[0037]

[0038] where w0 is the center angular frequency value, α is the natural frequency parameter, and b0, b1, b2, a1, a2 are the coefficients of the biquadratic filter.

[0039] The aforementioned center angular frequency value and the natural frequency parameter are obtained by the coefficient corrector according to the following formula:

[0040] where f k is the center frequency input by the noise bandwidth detector 42, F s is the frequency input by the reference microphone 12, Q is the default quality parameter, w0 is the center angular frequency value, and α is the natural frequency parameter. The aforementioned quality parameter Q is determined based on the quality factor; the natural frequency parameter α is determined based on the natural frequency factor.

[0041] The biquadratic filters 46 of order 1 to N correct the coefficients according to the bandwidth of the received error signal, and after eliminating the high-frequency noise of the error signal of the next sample according to the corrected coefficients (x[n-1], x[n-2] are regarded as known parameters), the error shaping signal is output by the biquadratic filter 46N of order N (step S205). The biquadratic filters 461-46N filter the error signal according to the following formula:

[0042] y[n] = b0 × x[n] + b1 × x[n-1] + b2 × x[n-2] - a1 × y[n-1] - a2 × y[n-2];

[0043] Wherein, x[n], x[n-1], and x[n-2] are error signals received at the nth, (n-1)th, and (n-2)th time points respectively, y[n], y[n-1], and y[n-2] are the error shaping signals output at the nth, (n-1)th, and (n-2)th time points respectively, and b0, b1, b2, a1, and a2 are the coefficients of the biquadratic filter 461-46N.

[0044] Subsequently, the LMS arithmetic unit 52 of the processor 50 receives the error shaping signal and the reference signal via the secondary path filter 56 to update the coefficients of the adaptive filter 54, so that the adaptive filter 54 adjusts the received reference signal into a noise reduction signal with the same magnitude and opposite phase as the environmental noise NS, and outputs the noise reduction signal to the audio output device 30 (step S206).

[0045] Finally, the audio output device 30 converts the received noise reduction signal into an audio signal of analog audio, and eliminates the environmental noise NS with the audio signal (step S207).

[0046] In summary, compared with the prior art, the present application can reduce the high-frequency noise of the error signal compared with the existing technology, and can adjust the eliminated high-frequency noise according to requirements. Furthermore, it can avoid the operation divergence of the adaptive filter, resulting in a reduction in the noise reduction effect.

[0047] The present application has been described in detail above. However, the above content is only the preferred embodiment of the present application, and the scope of implementation of the present application cannot be limited thereby. That is, all equal changes and modifications made according to the patent scope of the present application should still fall within the patent coverage of the present application.

Claims

1. A dual second-order error quantity integer active noise cancellation system, characterized in that, Comprising: A reference signal receiving device, which receives a reference sound source signal and outputs a reference signal; An error signal receiving device, which receives an error sound source signal and outputs an error signal; An audio output device, which outputs an audio signal; An error shaper, the input end of the error shaper is connected to the error signal receiving device to receive the error signal, the error shaper includes a noise bandwidth detector, a coefficient corrector with its input end connected to the noise bandwidth detector, and a 1st to Nth order biquadratic filter with its input end connected to the coefficient corrector. The noise bandwidth detector calculates the bandwidth of the error signal, the coefficient corrector corrects the coefficients of the 1st to Nth order biquadratic filter according to the bandwidth of the error signal, and the 1st to Nth order biquadratic filter eliminates the high-frequency noise of the downsampled error signal according to the corrected coefficients and outputs an error shaping signal from the 1st to Nth order biquadratic filter; And A processor, its input end is connected to the reference signal receiving device and the error shaper, the output end of the processor is connected to the audio output device, the processor includes an LMS operator and an adaptive filter with its input end connected to the LMS operator. The LMS operator updates the coefficients of the adaptive filter according to the received reference signal and the error shaping signal, and the adaptive filter outputs a noise reduction signal to the audio output device according to the updated coefficients.

2. The double second-order error quantity integer active noise cancellation system according to claim 1, characterized in that, The reference signal receiving device includes a reference microphone, a preamplifier connected to the rear end of the reference microphone, an anti-aliasing filter connected to the rear end of the preamplifier, and an analog-to-digital converter connected to the rear end of the anti-aliasing filter.

3. The double second-order error quantity integer type active noise cancellation system according to claim 1, characterized in that, The error signal receiving device includes an error microphone, a preamplifier connected to the rear end of the error microphone, an anti-aliasing filter connected to the rear end of the preamplifier, and an analog-to-digital converter connected to the rear end of the anti-aliasing filter.

4. The biquadratic error amount shaping active noise cancellation system according to claim 1, wherein The audio output device includes a speaker, a power amplifier connected to the front end of the speaker, a reconstruction filter connected to the front end of the power amplifier, and a digital-to-analog converter connected to the front end of the reconstruction filter.

5. The biquadratic error amount shaping active noise cancellation system according to claim 2, wherein The input end of the noise bandwidth detector is connected to the error signal receiving device to detect the bandwidth of the error signal and output a noise bandwidth signal with the same bandwidth as the center frequency of the error signal; Wherein, the input end of the coefficient corrector is connected to the reference microphone to receive the reference microphone signal, and calculates and outputs a coefficient correction signal for adjusting the coefficients of the biquadratic filter to the 1st to Nth order biquadratic filter according to the reference microphone signal and the noise bandwidth signal; Among them, the input end of the first-order biquadratic filter is connected to the error signal receiving device to receive the error signal. The first- to N-order biquadratic filters update coefficients according to the coefficient correction signal, correct the error signal of the next sample according to the updated coefficients, and then the N-order biquadratic filter outputs the error integer signal.

6. The biquadratic error amount integer active noise cancellation system according to claim 5, wherein the biquadratic filter filters the error signal according to the following formula: y[n] = b0×x[n] + b1×x[n - 1] + b2×x[n - 2] - a1×y[n - 1] - a2×y[n - 2]; wherein, x[n], x[n - 1], x[n - 2] are the error signals received at the nth, (n - 1)th, and (n - 2)th time points, y[n], y[n - 1], y[n - 2] are the error integer signals output at the nth, (n - 1)th, and (n - 2)th time points, and b0, b1, b2, a1, a2 are the coefficients of the biquadratic filter.

7. The biquadratic error amount integer active noise cancellation system according to claim 6, wherein the coefficient corrector corrects the coefficients of the biquadratic filter according to the following formula: wherein, w0 is the central angular frequency value, α is the natural frequency parameter, and b0, b1, b2, a1, a2 are the coefficients of the biquadratic filter.

8. The biquadratic error amount integer active noise cancellation system according to claim 7, wherein the central angular frequency value and the natural frequency parameter are obtained by the coefficient corrector according to the following formula: where f k is the center frequency input by the noise bandwidth detector, F s is the frequency input by the reference microphone, Q is the default quality parameter, w0 is the central angular frequency value, and α is the natural frequency parameter.

9. The biquadratic error amount integer active noise cancellation system according to claim 8, wherein the central frequency is obtained by the noise bandwidth detector from the error signal according to the following formula: k = 0, ……, M - 1; where x[n] is the error signal input by the error receiving device at the nth stage, and f k is the center frequency output by the noise bandwidth detector, and f k has M outputs, where M is a preset number of outputs.

10. The biquadratic error amount integer active noise cancellation system according to claim 8, wherein the quality parameter is determined based on the quality factor, and the natural frequency parameter is determined based on the natural frequency factor.

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