Adaptive active noise cancellation device and sound playing system using the same

Abstract

The present invention relates to an adaptive active noise cancellation device and a sound playing system using the same. The adaptive active noise cancellation device shapes a received error signal and an interference signal according to a shape of an ideal noise, and then sends the shaped interference signal and the shaped error signal to a parameter adjustment unit to perform adaptive parameter adjustment. Thus, the adaptive active noise cancellation device can not only adaptively suppress external noise to minimize the error signal, but also suppress specific frequencies to which human ears are sensitive.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of noise cancellation, and in particular to an adaptive active noise cancellation device and a sound playing system using the same. BACKGROUND

[0002] The noise reduction technology of general earphones is divided into passive noise cancellation (PNC) and active noise cancellation (ANC). Passive noise cancellation mainly isolates noise through earphone sound insulation materials or special structures. Generally, it is an earplug or a full-cover earphone, which will cause ear swelling and pain after long-term wearing, and even affect hearing at a large sound pressure. Active noise cancellation is to set a dedicated noise reduction circuit in the earphone, which generally receives, analyzes the frequency of external noise through an audio receiver (such as a microphone) and an anti-noise output chip, and generates an opposite sound wave to cancel the noise through the destructive interference of the sound wave.

[0003] In addition, the active noise cancellation technology is divided into a factory preset active noise cancellation filter (ANC filter) and an adaptive ANC filter in the noise cancellation part. The adaptive ANC filter basically generates different noise cancellation transfer functions according to different environmental noises, and gradually converges by comparing the error between the noise and the generated anti-noise according to the number and time of adaptive ANC filter operation, thereby eliminating the noise. The existing adaptive ANC filter provides different noise cancellation capabilities under different environmental noises, and is relatively unreliable. How to reduce the influence of environmental noise on noise cancellation capability has become an important work project in this field. SUMMARY

[0004] Therefore, how to alleviate or eliminate the defects of the above-mentioned related field, and at the same time make the adaptive active noise cancellation filter technology meet the environmental noise to suppress the noise, is a problem to be solved.

[0005] The present invention relates to an active noise cancellation system, which outputs an anti-noise signal according to a reference noise signal. The active noise cancellation system comprises an error microphone and an adaptive active noise cancellation device. The error microphone receives an ambient noise signal and the reference noise signal to generate an error signal. The adaptive active noise cancellation device comprises an automatic noise shaping circuit, an adaptive active noise filter unit, a first transfer path modeling unit and a parameter adjustment unit. The automatic noise shaping circuit receives the error signal, shapes the error signal into a shaped error signal and an interference signal into a shaped interference signal according to a predetermined noise shape, and outputs the shaped interference signal and the shaped error signal. The adaptive active noise filter unit receives the shaped interference signal and outputs an anti-noise signal for generating the reference noise signal. The first transfer path modeling unit receives the shaped interference signal and generates a modeled shaped interference signal according to a transfer function. The parameter adjustment unit receives the modeled shaped interference signal and the shaped error signal, adjusts filter coefficients of the adaptive active noise filter unit according to the modeled shaped interference signal and the shaped error signal using an adaptive algorithm.

[0006] In a preferred embodiment of the present invention, when the active noise cancellation system is a feedback active noise cancellation earphone, the interference signal is a restored ambient noise signal. In another preferred embodiment of the present invention, when the active noise cancellation system is a feedforward active noise cancellation earphone, the active noise cancellation system further comprises an external noise receiving microphone for receiving an external noise signal and converting the external noise signal into the interference signal.

[0007] The present invention shapes the error signal and the interference signal according to a predetermined noise shape before the shaped error signal and the shaped interference signal are sent to the parameter adjustment unit for adaptive parameter adjustment. Thus, the adaptive active noise filter unit can effectively suppress the external noise and the noise in the ear canal to minimize the error signal, and can suppress the specific frequencies sensitive to human ears.

[0008] Other advantages of the present invention will be described in detail with the following description and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0009] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:

[0010] Figure 1 A frequency response diagram showing the ideal noise and the noise after the adaptive active noise cancellation function is turned on.

[0011] Figure 2A frequency response plot of ambient noise and noise level after activating adaptive active noise cancellation.

[0012] Figure 3 A schematic diagram of an active noise reduction earphone according to a preferred embodiment of the present application.

[0013] Figure 4 A circuit block diagram of a sound playing system according to a preferred embodiment of the present application.

[0014] Figure 5 A circuit block diagram of a sound playing system according to a preferred embodiment of the present application.

[0015] Figure 6 A circuit block diagram of a sound playing system according to a preferred embodiment of the present application.

[0016] Figure 7 A circuit block diagram of a sound playing system according to a preferred embodiment of the present application.

[0017] Figure 8 A circuit block diagram of a sound playing system according to a preferred embodiment of the present application.

[0018] Figure 9 A circuit block diagram of a sound playing system according to a preferred embodiment of the present application.

[0019] Figure 10 A circuit block diagram of a sound playing system according to a preferred embodiment of the present application.

[0020] Figure 11 A circuit block diagram of a sound playing system according to a preferred embodiment of the present application.

[0021] Figure 12 A circuit block diagram of a sound playing system according to a preferred embodiment of the present application.

[0022] Figure 13 A circuit block diagram of a sound playing system according to a preferred embodiment of the present application.

[0023] Brief descriptions of the symbols in the drawings are as follows:

[0024] 101: ideal noise pattern; 102: noise suppression result of the ideal noise pattern; 103: general environmental noise; 104: noise suppression result for the general environmental noise 103; 301: left wireless earphone; 302: right wireless earphone; 303: mobile device; 40: transmission channel; 41: adaptive active noise cancellation device; 42: sound channel response schematic block; 411: external noise receiving microphone; 412: error microphone; 413: automatic noise shaping circuit; 414: adaptive active noise filter unit; 415: first transmission channel analog unit; 416: parameter adjustment unit; 417: second transmission channel analog unit; 418: first adding circuit; 419: shaping filter parameter generation unit; 420: first shaping filter; 421: second adding circuit; 422: second shaping filter; 601, 901: third shaping filter; 1001, 1201: feed-forward active noise cancellation circuit; 1002, 1102: feedback active noise cancellation circuit; 1003: adder; 1004: feed-forward adaptive active noise filter unit; 1006: third shaping filter; 1010: third transmission channel analog unit; 1020: second parameter adjustment unit; 1005: feedback adaptive active noise filter unit; 1101: feed-forward noise reduction circuit; 1202: feedback noise reduction circuit; 1203: feedback noise filter unit; 1301: frequency analysis circuit; 1302: noise shape storage circuit; 1303: parameter operation circuit. DETAILED DESCRIPTION

[0025] Embodiments of the present application will be described below with reference to the accompanying drawings. In these drawings, the same reference numbers indicate the same or similar components or method flows.

[0026] It must be understood that the terms "comprising", "including", "containing", etc. used in the specification are used to denote the presence of a stated technical feature, integer, method step, operation process, component, and / or component, but do not exclude the presence of one or more other technical features, integers, method steps, operation processes, components, components, or any combination thereof.

[0027] The terms such as "first", "second", "third", etc. used in the present application are used to modify the components in the claims, and are not used to indicate the priority order, the precedence relationship, or the time sequence of one component before another component, or the time sequence of the execution of the method steps, but are only used to distinguish the components with the same name.

[0028] It must be understood that when a component is referred to as being "connected" or "coupled" to another component, it can be directly linked to the other component or coupled to the other component via another component. Conversely, when a component is referred to as being "directly connected" or "directly coupled" to another component, there are no intermediate components between them. Other words used to describe the relationship between components should be interpreted similarly, e.g., "between" versus "directly between", or "adjacent" versus "directly adjacent", etc.

[0029] Figure 1 A frequency response diagram of the noise level versus frequency is shown for an ideal noise and the noise level after the adaptive active noise cancellation function is turned on. Please refer to Figure 1 , where the horizontal axis is frequency and the vertical axis is amplitude. When the noise is an ideal noise pattern as shown in reference numeral 101, the noise suppression result is similar to that shown in reference numeral 102. The noise suppression is quite good. However, the ambient noise in general environment is not as ideal as the noise shown in reference numeral 101. Figure 1

[0030] Figure 2 A frequency response diagram of the noise level versus frequency is shown for an ideal noise and the noise level after the adaptive active noise cancellation function is turned on. Please refer to Figure 2 , where the horizontal axis is frequency and the vertical axis is amplitude. When the noise is an ideal noise pattern as shown in reference numeral 101, the noise suppression result is similar to that shown in reference numeral 102. The noise suppression is quite good. However, the ambient noise in general environment is not as ideal as the noise shown in reference numeral 101. Figure 1

[0031] Figure 3 A schematic diagram of an active noise reduction earphone is shown in a preferred embodiment of the present application. Please refer to Figure 3 In this embodiment, a wireless earbud is taken as an example. The wireless earbud is a pair of devices with wireless communication capability, including a left wireless earbud 301 and a right wireless earbud 302. The left wireless earbud 301 and the right wireless earbud 302 are not connected to each other by a physical wire.

[0032] The mobile device 303 and the left wireless earphone 301, and the mobile device 303 and the right wireless earphone 302 can use a wireless communication protocol to transmit packets carrying voice signals or music of the user, such as Bluetooth audio transmission model protocol (A2DP) packets.

[0033] In other embodiments, the mobile device 303 and the left wireless earphone 301, and the mobile device 303 and the right wireless earphone 302 can also use other point-to-point (P2P) wireless communication protocols such as Wi-Fi Direct, and the present application is not limited thereto. In the above embodiments, the active noise reduction earphone is exemplified by a wireless earphone, but those skilled in the art should know that the active noise reduction earphone can also be implemented by a wired earphone, and the present application is not limited thereto.

[0034] Figure 4 A circuit block diagram of a sound playback system according to a preferred embodiment of the present application is shown. Referring to Figure 4 The sound playback system includes an adaptive active noise cancellation device 41, an external noise receiving microphone 411, and an error microphone 412. The adaptive active noise cancellation device 41 includes an automatic noise shaping circuit 413, an adaptive active noise filter unit 414, a first transmission channel analog unit 415, and a parameter adjustment unit 416. In this embodiment, a feed-forward active noise reduction earphone is exemplified.

[0035] It should be noted that the sound playback system involves both the acoustic domain and the electrical domain. For example, the symbols d(n) and y(n) shown in the diagram represent acoustic signals in the acoustic domain, and the other symbols represent electrical signals in the electrical domain. However, in order to simplify the analysis, in the following, the electrical signals and the acoustic signals are not distinguished unless necessary.

[0036] The sound channel response schematic block 42 can be referred to as a main path, which represents a reference microphone (e.g., the external noise receiving microphone 411) and a reference signal (e.g., the signal d(n)) in the acoustic domain. Figure 4In some embodiments, the reference microphone is used to evaluate the transfer of the acoustic signal from the transmission between the reference microphone 411 to the error microphone 412, thereby analyzing the transformation of the acoustic signal after the transmission, where the analog result of the transmission is represented by the transfer function P(z). Ideally, the transfer function P(z) is evaluated based on the acoustic signal received by the reference microphone 411 and the acoustic signal received by the error microphone 412. However, in practice, it is not possible to obtain the acoustic signal, and thus the acoustic signal is replaced by the related electrical signal for analysis to obtain the transfer function P(z). In some possible embodiments, the adaptive active noise cancellation device 41 is disabled, and the transfer function P(z) is evaluated based on the signal x(n) obtained via the reference microphone 411 and based on the signal e(n) obtained via the error microphone 412, where no signal y(n) is generated because the adaptive active noise cancellation device 41 is disabled. Therefore, the signal e(n) is substantially the same as the signal d(n).

[0037] The transmission path 40 can be referred to as a secondary path, which is used to represent the transmission from the adaptive active noise filter unit 414 to the error microphone 412, thereby analyzing the transformation of the electrical signal output by the adaptive active noise filter unit 414 after the transmission, where the analog result of the transmission is represented by the path transfer function S(z). In some possible embodiments, the external noise source is removed, and the transfer function S(z) is evaluated based on the signal y'(n) output by the adaptive active noise filter unit 414 and based on the signal e(n) obtained via the error microphone 412, where no ambient noise d(n) exists because there is no external noise source. Therefore, the signal e(n) is substantially the same as the signal y(n).

[0038] The external noise receiving microphone 411 receives an external sound noise (e.g., ambient noise) and converts the external sound noise into a digital interference signal x(n). The adaptive active noise filter unit 414 receives the interference signal x(n) and outputs an inverted noise signal y'(n) based on the interference signal x(n).

[0039] The error microphone 412 receives the ambient noise d(n) in the ear canal and the anti-noise sound signal y(n), and converts a digital error signal e(n) therefrom, wherein the external sound noise is converted into the ambient noise d(n) via the sound channel response schematic block 42. Since the ambient noise d(n) and the anti-noise sound signal y(n) are both analog sound signals, in the acoustic domain, the above-mentioned ambient noise d(n) and the anti-noise sound signal y(n) interfere with each other in the ear canal. For the convenience of description, an adder symbol 43 is additionally shown in the figure. Those skilled in the art should know that the adder symbol 43 is not a physical element, but is used to represent the interference phenomenon of the two analog sounds.

[0040] The adaptive active noise filter unit 414 is used to generate an anti-noise signal y'(n) based on the interference signal x(n) and the error signal e(n), and the anti-noise signal y'(n) is converted into the anti-noise sound signal y(n) via the transmission channel 40. In some embodiments, the adaptive active noise filter unit 414 includes a finite impulse response (FIR) filter. In detail, in the embodiments of the present application, the adaptive active noise filter unit 414 is an adaptive filter that adjusts the coefficients in an iterative process, for example, by learning and algorithm. In an ideal case, after the sound signals interfere with each other, the anti-noise sound signal y(n) can completely eliminate the ambient noise d(n), so that the error signal e(n) tends to zero. However, in actual noise elimination, due to different filter designs and different filter coefficient algorithms, the noise in certain frequency bands is not easy to eliminate (especially low-frequency noise which is more sensitive to human ears). At the same time, in a real environment, due to the continuous change of external sound noise, the actual effect of noise elimination will also change continuously, making the user hear the noise that is large and small.

[0041] Accordingly, ideally, one possible way is to shape the external sound noise to reduce the degree of change of the ambient noise, so that the noise reduction filter can generate an effective anti-noise signal based on the low-variation noise provided by the microphone. However, in practice, it is difficult to shape the external sound noise propagating in the air. An alternative way is to shape the interference signal x(n) generated by the external noise receiving microphone 411 and the error signal e(n) generated by the error microphone 412.

[0042] In addition, since the external sound noise will change at any time, it is necessary to dynamically adjust the shaping method. Since the ambient noise d(n) is derived from the external sound noise, the degree of change of the external sound noise can be identified by analyzing the ambient noise d(n).

[0043] The automatic noise shaping circuit 413 of the present application is designed based on the above reasons, thus effectively suppressing the ambient noise d(n) and also suppressing the specific frequency (usually low frequency) that is more sensitive to human ears. Details are described as follows.

[0044] The automatic noise shaping circuit 413 in this embodiment includes a second transmission channel analog unit 417, a first adding circuit 418, a shaping filter parameter generating unit 419, a first shaping filter 420, a second adding circuit 421 and a second shaping filter 422. In some embodiments, the automatic noise shaping circuit 413 can be realized by a digital signal processor (DSP).

[0045] As described above, the automatic noise shaping circuit 413 is used to shape the interference signal x(n) generated by the external noise receiving microphone 411 and the error signal e(n) generated by the error microphone 412, and provides the shaped signals to the parameter adjusting unit 416, so that the input signal received by the parameter adjusting unit 416 can have the characteristics of the current ambient noise and can also adjust the frequency band distribution energy of the input signal. Therefore, the anti-noise signal y'(n) generated by the adaptive active noise filter unit 414 can effectively suppress the ambient noise d(n) and also suppress the specific frequency (usually low frequency) that is more sensitive to human ears.

[0046] Therefore, in this embodiment, the first shaping filter 420 is used to shape the interference signal x(n) and generate a shaped interference signal x'(n), and the second shaping filter 422 is used to shape the restored error signal and generate a shaped error signal The first shaping filter 420 and the second shaping filter 422 are, for example, digital filters (or equalizers), and the shaping filter parameters of the two shaping filters 420 and 422 are generated by a shaping filter parameter generating unit 419. The first shaping filter 420 receives the first shaping filter parameters. The second shaping filter 422 receives the second shaping filter parameters.

[0047] In order to generate effective shaping filter parameters, the shaping filter parameter generating unit 419 is used to analyze the ambient noise d(n), thereby identifying the degree of variation of the external sound noise. From the analysis of the ambient noise d(n), the shaping filter parameter generating unit 419 can identify the degree of variation of the external sound noise, and then generate the shaping filter parameters based on the degree of variation of the external sound noise. Figure 4The error microphone 412 receives not the ambient noise d(n) but the error signal e(n). The error signal e(n) is the result of the interference of the ambient noise d(n) and the inverted noise sound signal y(n). In the present embodiment, the error signal e(n) received by the error microphone 412 is subtracted from the inverted noise sound signal y(n) to recover the ambient noise d(n) in order to enable the shaping filter parameter generation unit 419 to obtain the ambient noise d(n) affected by the acoustic transfer function of the sound path 42.

[0048] To this end, the automatic noise shaping circuit 413 further comprises a second transmission path analog unit 417. The second transmission path analog unit 417 is configured to analogize the transfer function S(z) of the transmission path 40 in the electrical domain and to convert the inverted noise signal y'(n) into an analog inverted noise signal The error signal e(n) is subtracted from the analog inverted noise signal to recover the ambient noise d(n). The analog inverted noise signal is similar to the electrical signal corresponding to the inverted noise sound signal y(n). The difference is that the inverted noise sound signal y(n) belongs to the acoustic domain, whereas the analog inverted noise signal belongs to the electrical domain. Therefore, the transfer function of the second transmission path analog unit 417 is denoted by to distinguish the acoustic transfer function S(z) from the electrical analog transfer function

[0049] The analog inverted noise signal is then received by a first adding circuit 418 together with the error signal e(n) to subtract the analog inverted noise signal from the error signal e(n) to generate a recovered ambient noise signal The recovered ambient noise signal can be considered as a signal identical to the ambient noise d(n). Likewise, the ambient noise d(n) belongs to the acoustic domain, whereas the recovered ambient noise signal belongs to the electrical domain. The shaping filter parameter generation unit 419 receives the recovered ambient noise signal and generates, based on the internally stored predetermined noise shape and the recovered ambient noise signal first shaping filter parameters for the first shaping filter 420 and second shaping filter parameters for the second shaping filter 422.

[0050] In addition, a second adding circuit 421 receives the analog inverted noise signal and the recovered ambient noise signal a reduced error signal Similarly, the reduced ambient noise signal is obtained by subtracting the analog anti-phase noise signal from the error signal e(n). Thus, the embodiment will reduce the ambient noise signal and add the analog anti-phase noise signal to obtain an error signal e(n) that is approximately the original error signal e(n). For the sake of distinction, the reduced error signal is denoted, for example, as . The second shaping filter 422 receives the reduced error signal and shapes the reduced error signal to obtain a shaped error signal and inputs the shaped error signal to the parameter adjustment unit 416.

[0051] On the other hand, the interference signal x(n) output by the external noise receiving microphone 411 is also filtered by the first shaping filter 420. In the present embodiment, the adaptive active noise cancellation device 41 uses a filtered-X least mean square (FxLMS) algorithm. In other embodiments, the adaptive active noise cancellation device 41 can use other algorithms. According to the FxLMS algorithm, the shaped interference signal x'(n) output by the first shaping filter 420 also needs to pass through the first transmission path analog unit 415. The first transmission path analog unit 415 is also used to analog the channel transfer function S(z) of the transmission path 40 in the electrical domain, to convert the shaped interference signal x'(n) into an analog shaped interference signal Note that, according to the mathematical principle of linear systems, the first transmission path analog unit 415 and the first shaping filter 420 are interchangeable in terms of their positions in the circuit architecture.

[0052] Thus, the parameter adjustment unit 416 can use, for example, a least mean square (LSM) algorithm to obtain the filter parameter W(z) of the adaptive active noise filter unit 414 according to the shaped error signal and the analog shaped interference signal and continuously adjust the output parameter W(z) according to the shaped error signal and the analog shaped interference signal to minimize the error signal e(n).

[0053] Figure 5 Fig. 1 is a circuit block diagram of a sound playback system according to a preferred embodiment of the present application. Please refer to Figure 4 and Figure 5 , in Figure 4In this embodiment, the second shaping filter 422 receives the restoration error signal ê(n), while Figure 5 In this embodiment, the second shaping filter 422 instead directly receives the original error signal e(n). The shaped error signal output by the second shaping filter 422 based on the error signal e(n) is mathematically represented as e'(n). The shaping filter parameter generation unit 419 still receives the restored ambient noise signal. Those with general knowledge in the relevant technical field can... Figure 4 From the embodiments and their corresponding descriptions, it is understood that the two embodiments are equivalent both mathematically and in terms of circuit operation. Therefore, further details will not be provided here. This embodiment is relative to... Figure 4 In this embodiment, an adder 421 can be saved. Therefore, the circuit is simpler and the cost is relatively lower.

[0054] Figure 6 The diagram illustrates a circuit block diagram of a sound playback system according to a preferred embodiment of the present invention. Please also refer to... Figure 4 as well as Figure 6 Similarly, the second shaping filter 422 in Figure 4 The original text is a collection of fragments and incomplete sentences, making it impossible to translate accurately. It appears to be a mix of technical terms exist Figure 6 In some embodiments, the second shaping filter 422 is modified, for example, to directly receive the restored ambient noise signal. And based on the restored environmental noise signal Generate a reshaping and restoration of the environmental noise signal Additionally, simulated inverted noise signal It also shapes the signal into a shaped analog inverted noise signal through an additional third shaping filter 601. The shaping filter parameter generation unit 419 similarly generates third shaping filter parameters for the third shaping filter 601. Furthermore, the adder 421 reshapes and restores the ambient noise signal. and the reshaping analog inverted noise signal Add them together to obtain the shaping error signal. Those with general knowledge in the relevant technical field can... Figure 4 As can be understood from the embodiments and their corresponding descriptions, the two embodiments are equivalent both mathematically and in terms of circuit operation. Therefore, they will not be described in detail here.

[0055] Figure 7 The diagram illustrates a circuit block diagram of a sound playback system according to a preferred embodiment of the present invention. Please also refer to... Figure 4 as well as Figure 7 This embodiment is similar to Figure 4 The biggest difference in the embodiments is that, Figure 7The sound playback system in this embodiment is a feedback active noise-canceling headphone. The characteristic of feedback active noise-canceling headphones is that they do not have an external noise-receiving microphone 411, but only an error microphone 412 located in the ear canal. Therefore, compared to... Figure 4 In this embodiment, the error signal e(n) generated by the error microphone 412 needs to be shaped by the automatic noise shaping circuit 413. Figure 4 In the embodiment, both the interference signal x(n) generated by the external noise receiving microphone 411 and the error signal e(n) generated by the error microphone 412 need to be shaped by the automatic noise shaping circuit 413.

[0056] In this embodiment of the invention, since the adaptive active noise cancellation device 41 employs, for example, the FxLMS algorithm, and according to the FxLMS algorithm architecture, the adaptive active noise cancellation device 41 should take an external noise as input. Therefore, in this embodiment, without an external noise receiving microphone 411, the restored ambient noise signal output by the first adder circuit 418 is used. As external noise. Among them, the above-mentioned Figure 4 As can be seen from the description, the environmental noise signal is restored. This is an electrical signal similar to the ambient noise d(n). In other words, this embodiment utilizes the reconstructed ambient noise signal. to replace Figure 4 The interference signal x(n) in the signal.

[0057] Compared to Figure 4 The first shaping filter 420 in this embodiment is used to restore the ambient noise signal from the input signal. For example. Same as Figure 4 The architecture, the first shaping filter 420 will restore the ambient noise signal. After shaping, a shaped and restored environmental noise signal is output. The data is transmitted to the first transmission channel simulation unit 415, processed by the first transmission channel simulation unit 415, and then output to the parameter adjustment unit 416. Since mathematical operations and circuitry are both related to… Figure 4 The embodiments are similar. Those skilled in the art can... Figure 8 The operation method of this embodiment can be inferred from the embodiments and their corresponding descriptions, so it will not be repeated here.

[0058] Figure 4 The diagram illustrates a circuit block diagram of a sound playback system according to a preferred embodiment of the present invention. Please also refer to... Figure 5 , Figure 8 as well as Figure 5 This embodiment also uses a feedback active noise-canceling headphone as an example for the sound playback system; however, similar to... Figure 4, the second shaping filter 422 originally receives the restored error signal Instead, the second shaping filter 422 directly receives the error signal e(n) in this embodiment. Since the mathematical operation and the circuit are similar to those of the embodiments of Figure 5 , Figure 4 The person with ordinary knowledge in the art can understand the operation method of this embodiment by the embodiments of Figure 5 , Figure 9 and their corresponding descriptions, and thus the detailed description is omitted here.

[0059] Figure 4 A circuit block diagram of a sound playback system according to a preferred embodiment of the present application is shown. Please refer to Figure 6 , Figure 9 and Figure 6 This embodiment is also exemplified by a feedback active noise reduction earphone as the sound playback system, however, similar to the embodiments of Figure 9 , Figure 4 , the second shaping filter 422 originally receives the restored error signal The second shaping filter 422 in this embodiment directly receives the restored ambient noise signal and generates a shaped restored ambient noise signal based on the restored ambient noise signal In addition, the analog anti-phase noise signal is also shaped into a shaped analog anti-phase noise signal by an additional third shaping filter 901. Further, the adder 421 adds the shaped restored ambient noise signal and the shaped analog anti-phase noise signal to obtain a shaped error signal Figure 6 Since the mathematical operation and the circuit are similar to those of the embodiments of Figure 4 , Figure 6 The person with ordinary knowledge in the art can understand the operation method of this embodiment by the embodiments of Figure 10 , and their corresponding descriptions, and thus the detailed description is omitted here.

[0060] Figure 4 A circuit block diagram of a sound playback system according to a preferred embodiment of the present application is shown. Please refer to Figure 7 , Figure 10 and Figure 4 In this embodiment, the sound playback system is exemplified by a hybrid active noise reduction earphone, in other words, the adaptive active noise cancellation device contains a feed-forward noise cancellation circuit 1001 and a feedback active noise cancellation circuit 1002 (separated by a dashed line in the figure). Compared to the embodiments of Figure 4the first shaping filter 420 of the first embodiment, the input signal of the first shaping filter 420 in this embodiment is the restored ambient noise signal to be shaped into a shaped restored ambient noise signal to be shaped into a shaped restored ambient noise signal The operation of the feed-forward noise cancellation circuit 1001 is similar to Figure 7 and its description, the operation of the feedback active noise cancellation circuit 1002 is similar to Figure 4 and its description.

[0061] The feed-forward noise cancellation circuit 1001 comprises at least a feed-forward adaptive active noise filter unit 1004 (the filter coefficients in the figure are represented as W FF (z)), a third shaping filter 1006, a third transmission channel simulation unit 1010, a second parameter adjustment unit 1020. In the operation of the feed-forward noise cancellation circuit 1001, the signal processing principle for the interference signal x(n) is the same as Figure 4 The third shaping filter 1006 is used to shape the interference signal x(n) into a shaped interference signal x'(n) and provide it to the third transmission channel simulation unit 1010. The third transmission channel simulation unit 1010 further converts the shaped interference signal x'(n) into an analog shaped interference signal based on the channel transfer function S(z) of the analog transmission channel 40 and provides it to the second parameter adjustment unit 1020. On the other hand, the shaped error signal is provided by the second shaping filter 422 in the feedback active noise cancellation circuit 1002, for example, and, in this embodiment, the signal processing principle for the error signal e(n) to be converted into a shaped error signal is the same as Figure 10 and will not be described in detail here.

[0062] In addition, in Figure 11 , a summer 1003 is included to superimpose the inverted noise signal y1'(n) output by the feed-forward adaptive active noise filter unit 1004 and the inverted noise signal y2'(n) output by the feedback adaptive active noise filter unit 1005 and output to the transmission channel 40.

[0063] In this embodiment, since both the feed-forward ANC circuit 1001 and the feedback ANC circuit 1002 are adaptive noise cancellation circuits, the interference signal x(n) and the error signal e(n) still need to be shaped by the shaping filters (e.g., the shaping filters 420, 422 and 1006) and the adaptive algorithms are operated to obtain the filter coefficients W FF (z) of the feed-forward adaptive ANC filter unit 1004 and the filter coefficients W FB (z) of the feedback adaptive ANC filter unit 1005, respectively. In the embodiments of the present application, the filter coefficients are obtained by using the iterative operation of the least mean square (LMS) method, but the present application is not limited thereto.

[0064] Figure 7 A circuit block diagram of a sound playback system according to a preferred embodiment of the present application is shown. Please refer to Figure 10 , Figure 11 and Figure 10 In this embodiment, the sound playback system is also exemplified by a hybrid active noise cancellation headphone, but the hybrid active noise cancellation headphone only has the feedback ANC circuit 1102 using adaptive noise cancellation, and the feed-forward noise cancellation circuit 1101 part uses static noise cancellation. Since static noise cancellation is used, compared with the feed-forward ANC circuit 1001 of Figure 4 , the second parameter adjustment unit 1020 and its related functional blocks, such as the third transmission channel analog unit 1010, have been removed in this embodiment, and the feed-forward noise cancellation circuit 1101 includes a static active noise filter unit 1105. The operation of the feedback ANC circuit 1102 can refer to the embodiments of Figure 7 and Figure 12 Therefore, they will not be described here.

[0065] Figure 4 A circuit block diagram of a sound playback system according to a preferred embodiment of the present application is shown. Please refer to Figure 10 , Figure 12 and Figure 7 In this embodiment, the sound playback system is also exemplified by a hybrid active noise cancellation headphone, but the hybrid active noise cancellation headphone only has the feed-forward ANC circuit 1201 using adaptive noise cancellation, and the feedback noise cancellation circuit 1202 part uses static active noise cancellation. The operation of the feedback noise cancellation circuit 1202 can refer to the embodiments of Figure 13The embodiments of the present application are not limited to the above-mentioned embodiments. For example, the feedback noise filter unit 1203 of the feedback noise reduction circuit 1202 can receive the interference signal as the error signal e(n) instead of the restored ambient noise signal

[0066] Figure 13 A circuit block diagram of the shaping filter parameter generating unit 419 of the sound playback system according to a preferred embodiment of the present application is shown. Referring to FIG. 13, the shaping filter parameter generating unit 419 according to the embodiment includes a frequency analysis circuit 1301, a noise shape storage circuit 1302, and a parameter operation circuit 1303. Figures 4 to 13 In the embodiment, the frequency analysis circuit 1301 is implemented by, for example, a fast Fourier transform (FFT) operation circuit, so that the time domain to frequency domain conversion of the received restored ambient noise signal is performed. The parameter operation circuit 1303 obtains the frequency domain parameters of the ideal noise stored in the noise shape storage circuit 1302, and divides the frequency domain parameters of the restored ambient noise signal by the frequency domain parameters of the ideal noise to obtain the shaping filter parameter W(z).

[0067] Although the above-mentioned embodiments are exemplified by using the fast Fourier transform and division, it should be understood by those skilled in the art that the above-mentioned operations can be implemented by different mathematical methods, and the present application is not limited thereto.

[0068] It should be noted that in the above-mentioned embodiments, the number of the shaping filters is at least two, and in order to obtain the same shaping filter effect for all noise or interference signals, the shaping filter parameters outputted by the shaping filter parameter generating unit to each shaping filter can be, for example, the same data. However, it should be understood by those skilled in the art that in actual circuit design applications, the shaping filter parameters outputted by the shaping filter parameter generating unit to each shaping filter can be different in order to adapt to the circuit design. In addition, in actual circuit design applications, the number of the shaping filters of the adaptive active noise cancellation device can be one, and the present application is not limited to the number of the shaping filters and the design of the shaping filter parameters.

[0069] In summary, the spirit of the present application is to shape the received error signal and the interference signal according to a shape of an ideal noise, and then send the shaped interference signal and the shaped error signal into a parameter adjustment unit to perform adaptive parameter adjustment. In this way, the adaptive active noise filter unit can effectively suppress external noise and ear canal noise, thereby minimizing the error signal, and can also suppress specific frequencies to which the human ear is sensitive.

[0070] Although ​ The above-described elements are included in the present application, but other additional elements can be used without departing from the spirit of the present application to achieve better technical effects. Therefore, the present application is not limited to using only the above-described sequence. In addition, those skilled in the art can integrate several steps into one step, or perform more steps sequentially or in parallel in addition to these steps, and the present application is not limited thereto.

[0071] The above description is only a preferred embodiment of the present application, and is not intended to limit the scope of the present application. Any person skilled in the art can make further improvements and changes on the basis of the present application without departing from the spirit and scope of the present application. Therefore, the protection scope of the present application shall be defined by the scope of the claims of the present application.

Claims

1. An adaptive active noise cancellation device adapted for use in a sound playing system, the sound playing system being configured to output an anti-noise sound signal in accordance with an anti-noise signal, wherein, The sound playing system comprises an error microphone for receiving ambient noise and the inverted noise sound signal to generate an error signal, and the adaptive active noise cancellation device comprises: an automatic noise shaping circuit receiving the error signal, shaping the interference signal into a shaped interference signal and shaping the error signal into a shaped error signal according to a preset noise shape, and outputting the shaped interference signal and the shaped error signal, wherein the automatic noise shaping circuit comprises: a shaping filter parameter generating unit for adjusting first and second shaping filter parameters based on the error signal; a first shaping filter for shaping the interference signal into the shaped interference signal based on the first shaping filter parameter; and a second shaping filter for shaping the error signal into the shaped error signal based on the second shaping filter parameter; an adaptive active noise filter unit receiving the interference signal and outputting the inverted noise signal for generating the inverted noise sound signal; a first transmission channel simulation unit receiving the shaped interference signal and generating a simulated shaped interference signal according to a channel transfer function; and a parameter adjusting unit receiving the simulated shaped interference signal and the shaped error signal, adjusting filter coefficients of the adaptive active noise filter unit according to the simulated shaped interference signal and the shaped error signal by using an adaptive algorithm.

2. The adaptive active noise cancellation device of claim 1, wherein, The automatic noise shaping circuit further comprises: a second transmission channel simulation unit receiving the inverted noise signal and generating a simulated inverted noise signal according to the channel transfer function; a first adding circuit receiving the simulated inverted noise signal and the error signal to generate a restored ambient noise signal, wherein the shaping filter parameter generating unit receives the restored ambient noise signal, and generates the first and second shaping filter parameters according to the preset noise shape and the restored ambient noise signal; and a second adding circuit receiving the simulated inverted noise signal and the restored ambient noise signal to generate a restored error signal, wherein the second shaping filter receives the second shaping filter parameter and the restored error signal to generate the shaped error signal.

3. The adaptive active noise cancellation device of claim 2, wherein, When the sound playing system is a feedback type active noise reduction earphone, the interference signal is the restored ambient noise signal.

4. The adaptive active noise cancellation device of claim 2, wherein, When the sound playing system is a feedforward type active noise reduction earphone, the sound playing system further comprises: an external noise receiving microphone for receiving external sound noise and converting it into the interference signal.

5. The adaptive active noise cancellation device of claim 1, wherein, The automatic noise shaping circuit further comprises: a second transmission channel simulation unit receiving the inverted noise signal and generating a simulated inverted noise signal according to the channel transfer function; and a first adding circuit receiving the simulated inverted noise signal and the error signal to generate a restored ambient noise signal, The shaping filter parameter generating unit receives the restored ambient noise signal, and generates the first shaping filter parameter and the second shaping filter parameter according to the preset noise shape and the restored ambient noise signal.

6. The adaptive active noise cancellation device of claim 5, wherein, When the sound playing system is a feedback type active noise reduction earphone, the interference signal is the restored ambient noise signal.

7. The adaptive active noise cancellation device of claim 5, wherein, When the sound playing system is a feedforward type active noise reduction earphone, the sound playing system further comprises: An external noise receiving microphone is used to receive external sound noise and convert it into the interference signal.

8. The adaptive active noise cancellation device of claim 1, wherein, The automatic noise shaping circuit further comprises: A second transmission channel analog unit receives the inverted noise signal and generates an analog inverted noise signal according to the channel transfer function; A first adding circuit receives the analog inverted noise signal and the error signal to generate a restored ambient noise signal, The shaping filter parameter generating unit receives the restored ambient noise signal, and generates the first shaping filter parameter, the second shaping filter parameter and a third shaping filter parameter according to the preset noise shape and the restored ambient noise signal. The second shaping filter receives the second shaping filter parameter and the restored ambient noise signal to generate a shaped restored ambient noise signal; A third shaping filter receives the third shaping filter parameter and the analog inverted noise signal to generate a shaped analog inverted noise signal; and A second adding circuit receives the shaped analog inverted noise signal and the shaped restored ambient noise signal to generate the shaped error signal.

9. The adaptive active noise cancellation device of claim 8, wherein, When the sound playing system is a feedback type active noise reduction earphone, the interference signal is the restored ambient noise signal.

10. The adaptive active noise cancellation device of claim 8, wherein, When the sound playing system is a feedforward type active noise reduction earphone, the sound playing system further comprises: An external noise receiving microphone is used to receive external sound noise and convert it into the interference signal.

11. The adaptive active noise cancellation device of claim 1, wherein, The sound playing system is a composite type active noise reduction earphone, wherein the interference signal is a restored ambient noise signal, and the sound playing system comprises: An external noise receiving microphone is used to receive external sound noise and convert it into a second interference signal; wherein the adaptive active noise cancellation device further comprises: An active noise filter unit receives the second interference signal and outputs a second inverted noise signal used to generate the inverted noise signal; A third adding circuit is used to receive the inverted noise signal and the second inverted noise signal to superimpose the inverted noise signal and the second inverted noise signal, The sound playing system outputs the inverted noise signal according to the inverted noise signal and the second inverted noise signal.

12. The adaptive active noise cancellation device of claim 11, wherein, The active noise filter unit is a feedforward type adaptive active noise filter unit, and the automatic noise shaping circuit is further used to shape the second interference signal into a second shaped interference signal according to the preset noise shape, wherein the adaptive active noise cancellation device further comprises: a third transfer channel simulation unit receiving the second shaped interference signal to generate a second simulated shaped interference signal according to the channel transfer function; and a second parameter adjustment unit receiving the second simulated shaped interference signal and the shaped error signal to dynamically adjust filter coefficients of the feed-forward adaptive active noise filter unit according to the second simulated shaped interference signal and the shaped error signal, so as to minimize the error signal.

13. The adaptive active noise cancellation device of claim 1, wherein, The sound playing system is a composite active noise reduction earphone, and the sound playing system further comprises: an external noise receiving microphone receiving external sound noise and converting into the interference signal; wherein the adaptive active noise cancellation device further comprises: a feedback noise filter unit receiving the error signal to output a second anti-noise signal for generating the anti-noise sound signal, a third adding circuit receiving the anti-noise signal and the second anti-noise signal to superimpose the anti-noise signal and the second anti-noise signal, wherein the sound playing system outputs the anti-noise sound signal according to the anti-noise signal and the second anti-noise signal.

14. The adaptive active noise cancellation device of claim 1, wherein, The shaping filter parameter generation unit comprises: a frequency analysis circuit receiving the restored ambient noise signal and performing frequency analysis algorithm on the restored ambient noise signal to obtain the frequency energy distribution corresponding to the restored ambient noise signal; a noise shape storage circuit storing the frequency energy distribution corresponding to the ideal noise; and a parameter calculation circuit calculating the ratio of the frequency energy distribution corresponding to the restored ambient noise signal and the frequency energy distribution corresponding to the ideal noise according to the frequency energy distribution corresponding to the ideal noise to obtain the shaping filter parameter.

15. A sound playing system, outputting an inverted noise sound signal according to an inverted noise signal, characterized in that, The sound playing system comprises: an error microphone receiving ambient noise and the anti-noise sound signal to generate an error signal; and an adaptive active noise cancellation device comprising: an automatic noise shaping circuit receiving the error signal, shaping the interference signal into a shaped interference signal and shaping the error signal into a shaped error signal according to a preset noise shape, and outputting the shaped interference signal and the shaped error signal, wherein the automatic noise shaping circuit comprises: a shaping filter parameter generation unit adjusting first shaping filter parameters and second shaping filter parameters based on the error signal; a first shaping filter shaping the interference signal into the shaped interference signal based on the first shaping filter parameters; and a second shaping filter shaping the error signal into the shaped error signal based on the second shaping filter parameters; an adaptive active noise filter unit receiving the interference signal to output the anti-noise signal for generating the anti-noise sound signal; a first transfer channel simulation unit receiving the shaped interference signal to generate a simulated shaped interference signal according to a channel transfer function; and a second transfer channel simulation unit receiving the shaped error signal to generate a simulated shaped error signal according to the channel transfer function. A parameter adjustment unit receives the analog shaped interference signal and the shaping error signal, and adjusts filter coefficients of the adaptive active noise filter unit according to the analog shaped interference signal and the shaping error signal by using an adaptive algorithm.

16. The voice playback system of claim 15, wherein, The automatic noise shaping circuit further comprises: A second transmission channel analog unit receives the inverted noise signal, and generates an analog inverted noise signal according to the channel transfer function; A first adding circuit receives the analog inverted noise signal and the error signal, and generates a restored ambient noise signal, The shaping filter parameter generation unit receives the restored ambient noise signal, and generates the first shaping filter parameter and the second shaping filter parameter according to the preset noise shape and the restored ambient noise signal; and A second adding circuit receives the analog inverted noise signal and the restored ambient noise signal, and generates a restored error signal, The second shaping filter receives the second shaping filter parameter and the restored error signal, and generates the shaping error signal.

17. The voice playback system of claim 16, wherein When the sound playing system is a feedback type active noise reduction earphone, the interference signal is the restored ambient noise signal.

18. The voice playback system of claim 16, wherein, When the sound playing system is a feedforward type active noise reduction earphone, the sound playing system further comprises: An external noise receiving microphone receives external sound noise, and converts the external sound noise into the interference signal.

19. The voice playback system of claim 15, wherein, The automatic noise shaping circuit further comprises: A second transmission channel analog unit receives the inverted noise signal, and generates an analog inverted noise signal according to the channel transfer function; and A first adding circuit receives the analog inverted noise signal and the error signal, and generates a restored ambient noise signal, The shaping filter parameter generation unit receives the restored ambient noise signal, and generates the first shaping filter parameter and the second shaping filter parameter according to the preset noise shape and the restored ambient noise signal.

20. The voice playback system of claim 19, wherein, When the sound playing system is a feedback type active noise reduction earphone, the interference signal is the restored ambient noise signal.

21. The voice playback system of claim 19, wherein, When the sound playing system is a feedforward type active noise reduction earphone, the sound playing system further comprises: An external noise receiving microphone receives external sound noise, and converts the external sound noise into the interference signal.

22. The voice playback system of claim 15, wherein, The automatic noise shaping circuit further comprises: A second transmission channel analog unit receives the inverted noise signal, and generates an analog inverted noise signal according to the channel transfer function; A first adding circuit receives the analog inverted noise signal and the error signal, and generates a restored ambient noise signal, The shaping filter parameter generation unit receives the restored ambient noise signal, and generates the first shaping filter parameter, the second shaping filter parameter and a third shaping filter parameter according to the preset noise shape and the restored ambient noise signal; The second shaping filter receives the second shaping filter parameter and the restored ambient noise signal, and generates a shaped restored ambient noise signal; a third shaping filter receiving the third shaping filter parameter and the analog anti-phase noise signal to generate a shaped analog anti-phase noise signal; and a second adder circuit receiving the shaped analog anti-phase noise signal and the shaped ambient noise signal to generate the shaped error signal.

23. The voice playback system of claim 22, wherein, When the sound playback system is a feedback active noise reduction earphone, the interference signal is the ambient noise signal.

24. The voice playback system of claim 22, wherein, When the sound playback system is a feedforward active noise reduction earphone, the sound playback system further comprises: an external noise receiving microphone receiving external sound noise and converting into the interference signal.

25. The voice playback system of claim 15, wherein, The sound playback system is a hybrid active noise reduction earphone, wherein the interference signal is an ambient noise signal, and the sound playback system comprises: an external noise receiving microphone receiving external sound noise and converting into a second interference signal; wherein the adaptive active noise cancellation device further comprises: an active noise filter unit receiving the second interference signal and outputting a second anti-phase noise signal used to generate the anti-phase noise signal; a third adder circuit receiving the anti-phase noise signal and the second anti-phase noise signal to superimpose the anti-phase noise signal and the second anti-phase noise signal, wherein the sound playback system outputs the anti-phase noise signal according to the anti-phase noise signal and the second anti-phase noise signal.

26. The voice playback system of claim 25, wherein, The active noise filter unit is a feedforward adaptive active noise filter unit, and the automatic noise shaping circuit is further used to shape the second interference signal into a second shaped interference signal according to the preset noise shape, wherein the adaptive active noise cancellation device further comprises: a third transmission channel analog unit receiving the second shaped interference signal to generate a second analog shaped interference signal according to the channel transfer function; and a second parameter adjustment unit receiving the second analog shaped interference signal and the shaped error signal, dynamically adjusting the filter coefficient of the feedforward adaptive active noise filter unit according to the second analog shaped interference signal and the shaped error signal, so as to minimize the error signal.

27. The voice playback system of claim 15, wherein, The sound playback system is a hybrid active noise reduction earphone, and the sound playback system further comprises: an external noise receiving microphone receiving external sound noise and converting into the interference signal; wherein the adaptive active noise cancellation device further comprises: a feedback noise filter unit receiving the error signal and outputting a second anti-phase noise signal used to generate the anti-phase noise signal, a third adder circuit receiving the anti-phase noise signal and the second anti-phase noise signal to superimpose the anti-phase noise signal and the second anti-phase noise signal, wherein the sound playback system outputs the anti-phase noise signal according to the anti-phase noise signal and the second anti-phase noise signal.

28. The voice playback system of claim 15, wherein, The shaping filter parameter generation unit comprises: a frequency analysis circuit receiving the restored ambient noise signal and performing a frequency analysis algorithm on the restored ambient noise signal to obtain a frequency energy distribution corresponding to the restored ambient noise signal; a noise shape storage circuit storing a frequency energy distribution corresponding to an ideal noise; and a parameter calculation circuit calculating a ratio of the frequency energy distribution corresponding to the restored ambient noise signal to the frequency energy distribution corresponding to the ideal noise based on the frequency energy distribution corresponding to the ideal noise to obtain a shaping filter parameter.

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