Adaptive active noise control system and adaptive active noise control method

Abstract

An adaptive active noise control system and an adaptive active noise control method. The adaptive active noise control system includes an active noise control circuit and a control circuit. The active noise control circuit generates an anti-noise signal and includes at least one adaptive filter. The control circuit receives a first input signal derived from a reference signal output by a reference microphone that collects ambient noise, receives a second input signal derived from an error signal output by an error microphone that collects residual noise after noise reduction, and performs a comparison operation based on a first characteristic value of the first input signal and a second characteristic value of the second input signal to control the at least one adaptive filter.

Description

Technical Field

[0001] This invention relates to noise reduction / cancellation, and more particularly to an adaptive active noise control system and related methods with double talk handling. Background Technology

[0002] Active noise control (ANC) eliminates unwanted noise based on the superposition principle. Specifically, anti-noise signals with the same amplitude but opposite phase are generated and combined with unwanted noise, causing the two noise signals to cancel each other out in a local quiet zone (e.g., the user's eardrum). For example, an adaptive ANC algorithm models the transfer function of noise from location A (e.g., a reference microphone) to location B (e.g., an error microphone or the user's eardrum), and then converts the ambient noise collected at location A into an anti-noise signal that can be used to eliminate noise at location B. However, when the target noise source is not ambient noise but another sound source (e.g., the user's own voice, i.e., near-end speech), the adaptive ANC algorithm derives an incorrect transfer function. This situation is known as "double talk," and an incorrect transfer function may fail to eliminate ambient noise, and in the worst case, may even increase noise.

[0003] Therefore, an adaptive active noise control system with bilateral call processing is needed to prevent filter coefficient divergence in the presence of near-end speech. Summary of the Invention

[0004] One of the objectives of this invention is to propose an adaptive active noise control system and related methods with bilateral call processing.

[0005] In one embodiment of the present invention, an adaptive active noise control system is disclosed. The adaptive active noise control system includes an active noise control circuit and a control circuit. The active noise control circuit is used to generate an anti-noise signal, wherein the active noise control circuit includes at least one adaptive filter. The control circuit is used to receive a first input signal obtained from a reference signal output by a reference microphone collecting ambient noise, and a second input signal obtained from an error signal output by an error microphone collecting noise-reduced residual noise. The control circuit performs a comparison operation based on a first characteristic value of the first input signal and a second characteristic value of the second input signal to control the at least one adaptive filter.

[0006] In another embodiment of the present invention, an adaptive active noise control method is disclosed. The adaptive active noise control method includes: generating an anti-noise signal via an active noise control circuit, wherein the active noise control circuit includes at least one adaptive filter; receiving a first input signal obtained from a reference signal, wherein the reference signal is generated by acquiring ambient noise; receiving a second input signal obtained from an error signal, wherein the error signal is generated by acquiring noise-reduced residual noise; and performing a comparison operation based on a first feature value of the first input signal and a second feature value of the second input signal to control the at least one adaptive filter.

[0007] The advantage of the adaptive active noise control system of the present invention is that the control circuit can freeze the adaptive adjustment of the filter coefficients during the period when the presence of bilateral call events is detected, thus avoiding filter coefficient divergence in the presence of near-end speech; in addition, the control circuit can greatly improve the active noise control performance during the period when bilateral call events are detected by the transfer function restoration. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of an adaptive active noise control system according to an embodiment of the present invention.

[0009] Figure 2 This is a schematic diagram of a first adaptive active noise control system with bilateral call processing according to an embodiment of the present invention.

[0010] Figure 3 This is a schematic diagram of a detection circuit according to an embodiment of the present invention.

[0011] Figure 4 This is a schematic diagram of a conversion function recovery circuit according to an embodiment of the present invention.

[0012] Figure 5 This is a schematic diagram of a second adaptive active noise control system with bilateral call processing according to an embodiment of the present invention.

[0013] Figure 6 This is a schematic diagram of a third adaptive active noise control system with bilateral call processing according to an embodiment of the present invention.

[0014] [Symbol Explanation]

[0015] 100, 200, 500, 600: Adaptive Active Noise Control System

[0016] 102: Reference Microphone

[0017] 104: Error Microphone

[0018] 106, 206, 506, 606: Active noise control circuit

[0019] 108, 208, 508, 608: Control circuit

[0020] 110: Noise Cancelling Speaker

[0021] 112: Adaptive Filter

[0022] 212, 512, 612_1, 612_2: Adaptive filters based on filter-x minimum mean square

[0023] 214, 222, 514, 516, 614_1, 614_2, 616: Filters

[0024] 224, 518, 618: Combined circuit

[0025] 226, 526, 626: Bilateral Call Detection Circuit / Bilateral Call Detection

[0026] 228, 400, 528, 628: Transition function recovery circuit / transition function restorer

[0027] 300: Detection Circuit

[0028] 302, 304: Feature extraction circuits

[0029] 306: Comparator Circuit

[0030] 402: Conversion function pool

[0031] x[n]: Reference signal

[0032] y[n]: Anti-noise signal

[0033] e[n]: Error signal

[0034] Estimated signal

[0035] FL: Flag signal

[0036] y'[n]: signal

[0037] P(z), S(z), W(z), W FF (z), W FB (z): Transformation function

[0038] S1: First input signal

[0039] S2: Second input signal

[0040] CV1: First eigenvalue

[0041] CV2: Second eigenvalue

[0042] TH: Predetermined critical value

[0043] w[n], w[ni]: Filter coefficients Detailed Implementation

[0044] Certain terms are used in the specification and claims to refer to specific elements. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same element. This specification and claims do not distinguish elements based on differences in name, but rather on differences in function. The terms "comprising" and "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." Furthermore, the terms "coupled" or "coupled" herein include any direct and indirect electrical connection means. Therefore, if a first device is described as coupled to a second device, it means that the first device can be directly electrically connected to the second device, or indirectly electrically connected to the second device through other devices and connection means.

[0045] Figure 1This is a schematic diagram of an adaptive active noise control system according to an embodiment of the present invention. The adaptive active noise control system 100 can be installed in headphones (e.g., in-ear headphones). In this embodiment, the adaptive active noise control system 100 includes a reference microphone 102, an error microphone 104, an active noise control circuit 106, a control circuit 108, and a noise-cancelling loudspeaker 110. Active noise control circuit 106 generates an anti-noise signal y[n] for noise reduction / cancellation. Specifically, the anti-noise signal y[n] can be a digital signal, which is transmitted to noise cancellation speaker 110 to play analog anti-noise, where the analog anti-noise is intended to reduce / cancel unwanted ambient noise through superposition. Since an adaptive active noise control algorithm is used by active noise control circuit 106, active noise control circuit 106 includes at least one adaptive filter 112. Each adaptive filter 112 is used to estimate an unknown transformation function of a primary path from reference microphone 102 to the location where noise reduction / cancellation is achieved. For example, the at least one adaptive filter 112 used by active noise control circuit 106 can be an adaptive filter based on least mean square (LMS). Please note that the number of adaptive filters 112 used by the active noise control circuit 106 depends on the active noise control architecture adopted by the active noise control circuit 106. For example, the active noise control circuit 106 can adopt an adaptive feed-forward active noise control architecture, an adaptive feedback active noise control architecture, or an adaptive hybrid active noise control architecture (which can be regarded as a combination of an adaptive feed-forward active noise control architecture and an adaptive feedback active noise control architecture).

[0046] Reference microphone 102 is used to collect ambient noise from an external noise source and generate a reference signal x[n]. Error microphone 104 is used to collect residual noise after noise reduction / cancellation and generate an error signal e[n]. Either the reference signal x[n] or the error signal e[n] can be used by active noise control circuit 106 to adaptively adjust the filter coefficients of at least one adaptive filter 112.

[0047] In this embodiment, the control circuit 108 is used to receive a first input signal obtained from the reference signal x[n], receive a second input signal obtained from the error signal e[n], and perform a comparison operation based on a first feature value of the first input signal and a second feature value of the second input signal to control at least one adaptive filter 112.

[0048] To better understand the technical features of the present invention, it is assumed that the control circuit 108 is applied to double talk processing. When the control circuit 108 is applied to double talk processing, the comparison operation performed by the control circuit 108 is for double talk detection, where the first feature value can be the energy of the first input signal and the second feature value can be the energy of the second input signal. However, this is only an example and is not a limitation of the present invention. That is, the use of the control circuit 108 is not limited to double talk processing, and / or the first and second feature values ​​are not limited to energy levels. In fact, any adaptive active noise control system that uses the control circuit 108 disclosed in this application to control the operation of at least one adaptive filter falls within the scope of the present invention. Furthermore, the first input signal used by the control circuit 108 can be directly set by the reference signal x[n], or can be indirectly obtained after some processing of the reference signal x[n]. Similarly, the second input signal used by the control circuit 108 can be directly set by the error signal e[n], or can be indirectly obtained after some processing of the error signal e[n]. These design changes all fall within the scope of this invention.

[0049] Figure 2 This is a schematic diagram of a first adaptive active noise control system with bilateral call processing according to an embodiment of the present invention. The adaptive active noise control system 200 includes an active noise control circuit 206 and a control circuit 208. Figure 1 The active noise control circuit 106 shown can be implemented by the active noise control circuit 206. Figure 1The control circuit 108 shown can be implemented by the control circuit 208. The conversion function of the acoustic channel (also called the primary path) between the reference signal x[n] (which is the ambient noise collected by the reference microphone 102) and the noise signal d[n] at the noise reduction / cancellation point can be expressed as P(z). The conversion function of the electro-acoustic channel (also called the secondary path) between the anti-noise signal y[n] (which is the output of the active noise control circuit 206) and the error signal e[n] (which is the residual noise collected by the error microphone 104) can be expressed as S(z). Therefore, regarding the acoustic superposition in the space between the active noise control circuit 206 and the error microphone 104, a signal y'[n] will be generated because the anti-noise signal y[n] passes through the conversion function S(z) of the secondary path. In this embodiment, the active noise control circuit 206 employs an adaptive feedforward active noise control architecture with an adaptive filter 212 based on filtered-x LMS (Fx-LMS). The filtered-x LMS-based adaptive filter 212 has a transfer function W(z) defined by the filter coefficients adaptively adjusted by the filtered-x LMS algorithm. Therefore, the active noise control circuit 206 also includes a transfer function... A filter 214, and a transformation function This is the estimation of the transformation function S(z) for the secondary path. The focus of this invention is the control mechanism of the adaptive filter 212. Since the adaptive feedforward active noise control using the filter-x least mean square algorithm is known to those skilled in the art, further details will not be elaborated here.

[0050] Regarding the control circuit 208, it includes a filter 222, a combining circuit 224, a two-sided call detection circuit (labeled "two-sided call detection") 226, and a transfer function restoration circuit (labeled "transfer function restorer") 228. In this embodiment, the filter 222 has a transfer function (It is an estimate of the transformation function S(z) of the secondary path), and combined with circuit 224 to subtract the output error signal e[n] of filter 222 to generate an estimated signal. Estimated signal The estimation of d[n] is given, where d[n] = P(z) * x[n], and P(z) is unknown. The bilateral call detection circuit 226 is used to perform bilateral call detection based on a first input signal S1 derived from the reference signal x[n] and a second input signal S2 derived from the error signal e[n], and generates a flag signal FL to indicate whether a bilateral call event has occurred due to near-end speech. In this embodiment, the first input signal S1 is set by the reference signal x[n], and the second input signal S2 is the estimated signal output by the combination circuit 224. Please note that filter 222 and combination circuit 224 can be optional components. For example, in a design variation, the first input signal S1 can be directly set by the reference signal x[n], and the second input signal S2 can be directly set by the error signal e[n]. Under certain operating conditions, the purpose of detecting the occurrence of bilateral call events can also be achieved, which also falls within the scope of this invention.

[0051] Figure 3 This is a schematic diagram of a detection circuit according to an embodiment of the present invention. Due to the inherent characteristics of near-end speech, the energy at a first location near the noise reduction / cancellation location (e.g., the location of error microphone 104) is higher than the energy at a second location far from the noise reduction / cancellation location (e.g., the location of reference microphone 102). Based on this observation, the bilateral call detection circuit 226 can be constructed by... Figure 3 The detection circuit 300 shown is used for implementation. In this embodiment, the detection circuit 300 includes multiple feature extraction circuits 302 and 304 and a comparison circuit 306. Feature extraction circuit 302 is used to obtain a first feature value CV1 of the first input signal S1, and feature extraction circuit 304 is used to obtain a second feature value CV2 of the second input signal S2. Comparison circuit 306 is used to compare the ratio between the first feature value CV1 and the second feature value CV2 with a predetermined threshold TH to generate a comparison result. Based on the comparison result, a flag signal FL is set, and the flag signal FL is transmitted at least to the adaptive filter 212 based on filter-x least mean square. For example, the first feature value CV1 can be the energy of the first input signal S1, the second feature value CV2 can be the energy of the second input signal S2, and comparison circuit 306 can compare the ratio of the first feature value CV1 to the second feature value CV2 (i.e., ...). The ratio is compared to the predetermined critical value TH. If the value is less than a predetermined threshold TH, the comparator circuit 306 determines that a two-way communication event has occurred and sets the flag signal FL to a first logic value (e.g., FL = 1). When the ratio... If the value is not less than a predetermined threshold TH, the comparator circuit 306 determines that no bilateral call event has occurred and sets the flag signal FL to a second logic value (e.g., FL = 0).

[0052] like Figure 2 As shown, the adaptive filter 212 based on the filter-x least mean square (LMS) is controlled by a flag signal FL. When the flag signal FL has a first logic value (i.e., FL = 1) indicating the presence of a bilateral call event, the adaptive filter 212 based on the LMS is instructed to freeze the adaptive adjustment of the filter coefficients. That is, when the flag signal FL is asserted by the bilateral call detection circuit 226, the transfer function W(z) estimated by the adaptive filter 212 based on the LMS remains unchanged. When the flag signal FL has a second logic value (i.e., FL = 0) indicating the absence of a bilateral call event, the adaptive filter 212 based on the LMS is instructed to resume the adaptive adjustment of the filter coefficients. That is, when the flag signal FL is deasserted by the bilateral call detection circuit 226, the transfer function W(z) estimated by the adaptive filter 212 based on the LMS is allowed to be updated by the LMS algorithm. Since the adaptive adjustment of the filter coefficients is frozen during the period when the bilateral call detection circuit 226 detects the presence of a bilateral call event, the adaptive filter 212 based on the minimum mean square of filter-x can avoid the filter coefficients from diverging in the presence of near-end speech.

[0053] Generally, bilateral call detection requires some processing time, so the flag signal FL is only set to be valid after the start time of the near-end speech. At the time when the bilateral call detection circuit 226 detects the bilateral call event, a set of filter coefficients w[n] currently being used by the adaptive filter 212 based on the filter-x least mean square may have been affected by the near-end speech and may represent an inaccurate transition function. To solve this problem, the present invention proposes to use a transition function recovery circuit 228 to temporarily store one or more sets of filter coefficients w[ni] previously used by the adaptive filter 212 based on the filter-x least mean square. The transition function recovery circuit 228 is also controlled by the flag signal FL set by the bilateral call detection circuit 226 and can be used to correct transition functions (i.e., filter coefficients) that are misled by sound sources that are not ambient noise sources.

[0054] Figure 4 This is a schematic diagram of a conversion function recovery circuit according to an embodiment of the present invention. Figure 2 The conversion function restoration circuit 228 shown can be derived from... Figure 4The transfer function recovery circuit 400 shown is used for implementation. The transfer function recovery circuit 400 has a transfer function pool 402, which can be implemented by a storage device (e.g., a memory), and is used to periodically store a set of filter coefficients w[n] currently being used by the adaptive filter 212 based on the filter-x least mean square. When the flag signal FL has a first logic level (e.g., FL = 1) to indicate the presence of a bilateral communication event, the transfer function recovery circuit 400 (especially the transfer function pool 402 of the transfer function recovery circuit 400) is instructed to output a set of filter coefficients w[ni] previously used by the adaptive filter 212 based on the filter-x least mean square to the adaptive filter 212 based on the filter-x least mean square, in order to update the set of filter coefficients w[n] currently being used by the adaptive filter 212 based on the filter-x least mean square. Since the set of filter coefficients w[ni] previously used by the adaptive filter 212 based on filter-x least mean square was determined by the filter-x least mean square algorithm in the absence of bilateral call events, the transfer function restoration applied to the adaptive filter 212 based on filter-x least mean square can effectively improve the active noise control performance during the period when bilateral call detection circuit 226 detects bilateral call events.

[0055] Figure 5 This is a schematic diagram of a second adaptive active noise control system with bilateral call processing according to an embodiment of the present invention. The adaptive active noise control system 500 includes an active noise control circuit 506 and a control circuit 508. Figure 1 The active noise control circuit 106 shown can be implemented by the active noise control circuit 506. Figure 1 The control circuit 108 shown can be implemented by the control circuit 508. In this embodiment, the active noise control circuit 506 employs an adaptive feedback active noise control architecture with an adaptive filter 512 based on the minimum mean square of the filter-x. The adaptive filter 512 based on the minimum mean square of the filter-x has a transfer function W(z) defined by the filter coefficients adaptively adjusted by the minimum mean square of the filter-x algorithm. Therefore, the active noise control circuit 506 also includes a transfer function... A filter 514, and a transfer function This is an estimate of the transformation function S(z) for the secondary path. In this feedback architecture, the active noise control circuit 506 also includes a filter 516 and a combination circuit 518, which are used together to generate the estimated signal from the measured error signal e[n]. The estimated signal This is an estimate of d[n] (d[n] = P(z) * x[n], where P(z) is unknown). Note that the reference signal x[n] (which is the ambient noise collected by the reference microphone 102) is used by the control circuit 508, but not by the active noise control circuit 506 with an adaptive feedback active noise control architecture. The focus of this invention is on the control mechanism of the adaptive filter 512. Since adaptive feedback active noise control using the filter-x least mean square algorithm is known to those skilled in the art, further details are not described here.

[0056] Regarding the control circuit 508, it includes a two-sided call detection circuit (labeled "two-sided call detection") 526 and a transformation function recovery circuit (labeled "transformation function restorer") 528. The two-sided call detection circuit 526 is used to perform two-sided call detection based on a first input signal S1 obtained from a reference signal x[n] and a second input signal S2 obtained from an error signal e[n], and generates a flag signal FL to indicate whether a two-sided call event has occurred. In this embodiment, the first input signal S1 is set by the reference signal x[n], and the second input signal S2 is an estimated signal output by the combination circuit 518 in the adaptive feedback active noise control architecture. However, this is only for illustrative purposes and is not intended to limit the invention. For example, in a design variation, the first input signal S1 can be set by the reference signal x[n], and the second input signal S2 can be set by the error signal e[n]. Under certain operating conditions, the purpose of detecting the occurrence of bilateral call events can also be achieved, which also falls within the scope of the invention.

[0057] In this embodiment, the bilateral call detection circuit 526 can be derived from... Figure 3 The detection circuit 300 shown is used to perform bilateral call detection; and the conversion function recovery circuit 528 can be implemented by... Figure 4 The transformation function recovery circuit 400 shown is implemented to perform transformation function recovery based on the filter-x least mean square adaptive filter 512. As those skilled in the art can understand from the above description... Figure 3 and Figure 4 The operating principles of the bilateral call detection circuit 526 and the conversion function recovery circuit 528 can be easily understood from the instruction manual paragraphs. For the sake of brevity, further explanation is omitted here.

[0058] Figure 6 This is a schematic diagram of a third adaptive active noise control system with bilateral call processing according to an embodiment of the present invention. The adaptive active noise control system 600 includes an active noise control circuit 606 and a control circuit 608. Figure 1The active noise control circuit 106 shown can be implemented by the active noise control circuit 606. Figure 1 The control circuit 108 shown can be implemented by the control circuit 608. In this embodiment, the active noise control circuit 606 adopts an adaptive hybrid active noise control architecture (which is... Figure 2 The adaptive feedforward active noise control architecture shown and Figure 5 The adaptive feedback active noise control architecture shown is a combination of two adaptive filters (612_1 and 612_2) based on the filter-x least mean square algorithm. The filter-x least mean square algorithm-based adaptive filter 612_1 has a transition function W defined by the filter coefficients adaptively adjusted by the filter-x least mean square algorithm. FF (z), therefore, regarding the adaptive feedforward active noise control architecture (which is part of the adaptive hybrid active noise control architecture), the active noise control circuit 606 includes a transition function A filter 614_1, and a transformation function This is an estimate of the transformation function S(z) for the secondary path. Furthermore, the adaptive filter 612_2 based on the filter-x least mean square algorithm has a transformation function W defined by the filter coefficients adaptively adjusted by the filter-x least mean square algorithm. FB (z), therefore, regarding the adaptive feedback active noise control architecture (which is another part of the adaptive hybrid active noise control architecture), the active noise control circuit 606 includes a transition function A filter 614_2, and a transformation function The active noise control circuit 606 includes an estimate of the transformation function S(z) for the secondary path, and also includes a filter 616 and a combination circuit 618, which are used together to generate the estimated signal from the measured error signal e[n]. The estimated signal This is an estimate of d[n] (d[n] = P(z) * x[n], where P(z) is unknown). The focus of this invention is on the control mechanism of adaptive filters 612_1 and 612_2. Since the adaptive hybrid active noise control using the filter-x least mean square algorithm is known to those skilled in the art, further details will not be elaborated here.

[0059] Regarding the control circuit 608, it includes a two-sided call detection circuit (labeled "two-sided call detection") 626 and a transformation function recovery circuit (labeled "transformation function restorer") 628. The two-sided call detection circuit 626 is used to perform two-sided call detection based on a first input signal S1 obtained from a reference signal x[n] and a second input signal S2 obtained from an error signal e[n], and generates a flag signal FL to indicate whether a two-sided call event has occurred. In this embodiment, the first input signal S1 is set by the reference signal x[n], and the second input signal S2 is an estimated signal output by the combination circuit 618 in the adaptive hybrid active noise control architecture. However, this is only for illustrative purposes and is not intended to limit the invention. For example, in a design variation, the first input signal S1 can be set by the reference signal x[n], and the second input signal S2 can be set by the error signal e[n]. Under certain operating conditions, the purpose of detecting the occurrence of bilateral call events can also be achieved, which also falls within the scope of the invention.

[0060] In this embodiment, the bilateral call detection circuit 626 can be derived from... Figure 3 The detection circuit 300 shown is used to perform bilateral call detection; and the conversion function recovery circuit 628 can be implemented by... Figure 4 The transformation function recovery circuit 400 shown is implemented to perform transformation function recovery for each of the adaptive filters 612_1 and 612_2 based on the filter-x minimum mean square. For example, the transition function recovery circuit 628 periodically stores a set of filter coefficients currently used by the adaptive filter 612_1 based on filter-x minimum mean square, and periodically stores a set of filter coefficients currently used by the adaptive filter 612_2 based on filter-x minimum mean square. Furthermore, when the bilateral call detection circuit 626 asserts the flag signal FL in response to the detection of a bilateral call event, the transition function recovery circuit 628 outputs a set of filter coefficients previously used by the adaptive filter 612_1 based on filter-x minimum mean square to update the set of filter coefficients currently used by the adaptive filter 612_1 based on filter-x minimum mean square, and outputs a set of filter coefficients previously used by the adaptive filter 612_2 based on filter-x minimum mean square to update the set of filter coefficients currently used by the adaptive filter 612_2 based on filter-x minimum mean square. As those skilled in the art can read the above description... Figure 3 and Figure 4 The operating principles of the bilateral call detection circuit 626 and the conversion function recovery circuit 628 can be easily understood from the instruction manual paragraphs. For the sake of brevity, further explanation is omitted here.

[0061] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made in accordance with the claims of the present invention shall be within the scope of the present invention.

Claims

1. An adaptive active noise control system, comprising: An active noise control circuit for generating an anti-noise signal, wherein the active noise control circuit includes at least one adaptive filter; and A control circuit is configured to receive a first input signal obtained from a reference signal output by a reference microphone acquiring ambient noise, and a second input signal obtained from an error signal output by an error microphone acquiring noise-reduced residual noise, and to perform a comparison operation based on a first characteristic value of the first input signal and a second characteristic value of the second input signal to control the at least one adaptive filter, wherein the control circuit includes: A filter for processing the anti-noise signal output by the at least one adaptive filter to generate a filtered anti-noise signal; and The circuit combines the filtered anti-noise signal and the error signal to generate the second input signal.

2. The adaptive active noise control system of claim 1, wherein the control circuit is used to perform the comparison operation for bilateral call detection.

3. The adaptive active noise control system as described in claim 1, wherein the control circuit comprises: The detection circuit is used to compare the ratio between the first feature value and the second feature value with a predetermined threshold value to generate a comparison result, set a flag signal based on the comparison result, and output the flag signal to the at least one adaptive filter. The at least one adaptive filter is controlled by the flag signal.

4. The adaptive active noise control system of claim 3, wherein, in response to a comparison result indicating that the ratio of the first characteristic value to the second characteristic value is less than the predetermined threshold value, the detection circuit sets the flag signal to instruct the at least one adaptive filter to freeze the adaptive adjustment of the filter coefficients.

5. The adaptive active noise control system as described in claim 3, wherein the control circuit further comprises: A transfer function recovery circuit is used to temporarily store a set of filter coefficients previously used by the at least one adaptive filter; and The transfer function recovery circuit is controlled by the flag signal.

6. The adaptive active noise control system of claim 5, wherein, in response to a comparison result indicating that the ratio of the first eigenvalue to the second eigenvalue is less than the predetermined threshold, the detection circuit sets the flag signal to instruct the transfer function recovery circuit to output the set of filter coefficients previously used by the at least one adaptive filter to update the set of filter coefficients currently being used by the at least one adaptive filter.

7. The adaptive active noise control system as described in claim 1, wherein the active noise control circuit adopts an adaptive feedforward active noise control architecture, an adaptive feedback active noise control architecture, or an adaptive hybrid active noise control architecture, wherein the adaptive hybrid active noise control architecture is a combination of an adaptive feedforward active noise control architecture and an adaptive feedback active noise control architecture.

8. An adaptive active noise control method, comprising: An anti-noise signal is generated by an active noise control circuit, wherein the active noise control circuit includes at least one adaptive filter. Receive a first input signal obtained from a reference signal, wherein the reference signal is generated by acquiring ambient noise; Receive a second input signal obtained from the error signal, wherein the error signal is generated by acquiring the denoised residual noise; and A comparison operation is performed based on the first feature value of the first input signal and the second feature value of the second input signal to control the at least one adaptive filter; The step of receiving the second input signal obtained from the error signal includes: A filtering operation is performed on the anti-noise signal output by the at least one adaptive filter to generate a filtered anti-noise signal; as well as The filtered noise signal and the error signal are combined to generate the second input signal.

9. The adaptive active noise control method of claim 8, wherein the comparison operation is performed to perform bilateral call detection.

10. The adaptive active noise control method of claim 8, wherein the step of performing the comparison operation based on the first feature value of the first input signal and the second feature value of the second input signal to control the at least one adaptive filter comprises: The comparison result is generated by comparing the ratio between the first eigenvalue and the second eigenvalue with a predetermined critical value; The flag signal is set based on the comparison result; and The flag signal is output to the at least one adaptive filter; The at least one adaptive filter is controlled by the flag signal.

11. The adaptive active noise control method of claim 10, wherein, in response to a comparison result indicating that the ratio of the first eigenvalue to the second eigenvalue is less than the predetermined threshold, the flag signal is set to instruct the at least one adaptive filter to freeze the adaptive adjustment of the filter coefficients.

12. The adaptive active noise control method as described in claim 10, further comprising: Temporarily store a set of filter coefficients that have previously been used by the at least one adaptive filter; and Based on the flag signal, the set of filter coefficients that were previously used by the at least one adaptive filter are selectively output to the at least one adaptive filter.

13. The adaptive active noise control method of claim 12, wherein, in response to a comparison result indicating that the ratio of the first eigenvalue to the second eigenvalue is less than the predetermined threshold, the flag signal is set to indicate that the set of filter coefficients previously used by the at least one adaptive filter should be output to the at least one adaptive filter to update the set of filter coefficients currently being used by the at least one adaptive filter.

14. The adaptive active noise control method as described in claim 8, wherein the active noise control circuit employs an adaptive feedforward active noise control architecture, an adaptive feedback active noise control architecture, or an adaptive hybrid active noise control architecture. The adaptive hybrid active noise control architecture is a combination of an adaptive feedforward active noise control architecture and an adaptive feedback active noise control architecture.

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