TWI802055B - Active noise cancellation integrated circuit for stacking multiple anti-noise signals, associated method, and active noise cancellation earbud using the same - Google Patents

Abstract

The invention relates to an active noise cancellation integrated circuit for stacking multiple anti-noise signals, an associated method, and an active noise cancellation earbud using the same. The method is adapted for speaker with multiple ANC filtering units. The method includes: acquire at least one anti-noise signal from the output of the ANC filtering units; respectively generating decoupled signals by processing the anti-noise signal with the transfer function of the noise channel and the operations of the residual ANC filtering units; performing a signal mixing, wherein the anti-noise signals is mixed with the decoupled signal; and mixing the mixed signal with audio signal to perform an audio playback such that the noise is cancelled.

Description

Active noise reduction integrated circuit capable of stacking multiple anti-noise signals, method and active noise reduction earphone using same

The present invention relates to a technology of noise elimination, especially an active noise reduction integrated circuit capable of stacking multiple anti-noise signals, a method and an active noise reduction earphone using the same.

Generally, the noise reduction technology of earphones is divided into passive noise cancellation (passive noise cancellation, PNC) and active noise cancellation (active noise cancellation, ANC). Passive noise cancellation is mainly to isolate noise as much as possible through earphone sound insulation materials or special structures. Generally, it is in-ear earplugs or full-ear earphones. If you wear them for a long time, your ears will swell and hurt, and excessive sound pressure may even affect your hearing. Active noise cancellation is to set a special noise reduction circuit in the earphone, generally through an audio receiver (such as a miniature microphone) and an anti-noise output chip, to receive and analyze external noise and generate an anti-phase sound wave, through the destructive interference of the sound wave to Cancels noise.

In addition, the above-mentioned active noise cancellation is generally divided into feed-forward ANC, feedback ANC and hybrid ANC. Feed-forward noise reduction is to place a noise reduction microphone outside the earphones, receive the noise outside the earphones through the microphone, process it with a digital signal processing integrated circuit, and convert it into an anti-noise signal. The feedback noise reduction is to place the noise reduction microphone inside the earphone to receive the user's sound signal in the ear canal and feedback it. to a digital signal processing integrated circuit to generate a noise-resistant signal. In addition, compound noise reduction uses two or more noise reduction microphones to receive noise, and generates multiple anti-noise signals through different digital signal processing integrated circuits, and then superimposes the sound wave signals to cancel the noise.

Since anti-phase sound waves are generated by multiple microphones in different positions and different signal processing, the final observation point receives multiple anti-phase sound waves superimposed, which leads to over-compensation, but makes people hear more noise. In view of this, how to alleviate or eliminate the deficiencies in the above-mentioned related fields is a problem to be solved.

The present invention provides an active noise reduction earphone. The active noise reduction earphone includes an audio conversion device and a stackable multiple active noise reduction integrated circuit according to an embodiment of the present invention. The stackable multiple active noise reduction integrated circuit includes A first path, outputting a first path anti-noise signal, wherein the first path anti-noise signal is converted into a first signal by a physical channel, and the first path includes: a first active noise elimination filter unit for A first anti-noise signal is generated; a second path receives an error signal containing a component of the first signal, and outputs a second path anti-noise signal to the physical channel, the second path includes: a second active a noise canceling filter unit for generating a second anti-noise signal, wherein the second anti-noise signal derives the second path anti-noise signal; and a first decoupling unit for shifting components of the first signal in the second path are removed.

The present invention also provides a stackable multiple active noise reduction method, which is suitable for a sound playback device with multiple active noise cancellation filter units. The stackable multiple active noise reduction method includes: providing a first path, outputting a first path anti-noise Noise signal, wherein the anti-noise signal of the first path is converted into a first signal by a physical channel, and the first path includes: a first active noise cancellation filter unit for generating a first anti-noise signal; providing a first Two paths, receiving an error signal containing components of the first signal signal, and output a second path anti-noise signal to the physical channel, the second path includes: a second active noise cancellation filter unit for generating a second anti-noise signal, wherein the second anti-noise signal is derived The anti-noise signal of the second path; remove the component of the first signal in the second path based on the first anti-noise signal; and play based on the anti-noise signal of the first path and the anti-noise signal of the second path, so as to Eliminate noise.

The spirit of the present invention is to set a plurality of active noise cancellation filter units in the active noise reduction device of the active noise reduction earphone. Further, for the output signal of each active noise cancellation filter unit, the redundant components generated by other active noise cancellation filter units are eliminated by decoupling. Therefore, the noise cancellation signal output by the active noise reduction device It can be more in line with the received noise, and then can properly cancel the noise.

Other advantages of the present invention will be explained in more detail with the following description and drawings.

101: left wireless earphone

102: Right wireless earphone

103:Mobile device

19: Earphone shell

20: Stackable multiple active noise reduction ICs

21:Audio conversion equipment

201: The first microphone

202:Second microphone

203: The first active noise cancellation filter unit

204: The second active noise cancellation filter unit

205, 72: physical channel

301: noise

302: Only enable the noise suppression result of the first active noise cancellation filter unit 203 (Feed Forward, FF)

303: Only enable the noise suppression result of the second active noise cancellation filter unit 204 (Feedback, FB)

304: Turn on the expected noise suppression results of the first active noise cancellation filter unit 203 and the second active noise cancellation filter unit 204 (FF+FB)

305: Turn on the real noise suppression results of the first active noise cancellation filter unit 203 and the second active noise cancellation filter unit 204 (FF+FB)

40, 50, 60: the first decoupling unit

70, 80: the second decoupling unit

401, 501: first channel analog filter

402, 503, 603: the first addition circuit

502, 601: the third active noise cancellation filter unit

504, 604, 702: the second addition circuit

601: The third active noise cancellation filter unit

602, 701, 801: second channel analog filter

603: The first addition circuit

604, 702, 802: the second addition circuit

71: Non-isolated headphones

91: The third active noise cancellation filter unit

90: The third decoupling unit

S1001~S1003: Steps of a stackable multiple active noise reduction method in a preferred embodiment of the present invention

FIG. 1 is a schematic diagram of an active noise canceling earphone according to a preferred embodiment of the present invention.

FIG. 2 is a schematic block diagram of an equivalent sampling time of an ANC earphone according to a preferred embodiment of the present invention.

Fig. 3 is a comparison diagram of the noise suppression results of the embodiment in Fig. 2.

FIG. 4 is a schematic block diagram of an equivalent sampling time of an ANC earphone with good isolation according to a preferred embodiment of the present invention.

FIG. 5 is a schematic block diagram of an equivalent sampling time of an ANC earphone with good isolation according to a preferred embodiment of the present invention.

FIG. 6 is a schematic block diagram of an equivalent sampling time of an ANC earphone with good isolation according to a preferred embodiment of the present invention.

FIG. 7 is a schematic block diagram of an equivalent sampling time of an ANC headphone without good isolation according to a preferred embodiment of the present invention.

FIG. 8 is a schematic block diagram of an equivalent sampling time of an ANC earphone according to a preferred embodiment of the present invention.

FIG. 9 is a schematic block diagram of an equivalent sampling time of an ANC earphone with good isolation according to a preferred embodiment of the present invention.

FIG. 10 is a flow chart of a stackable multiple active noise reduction method according to a preferred embodiment of the present invention.

The following description is a preferred implementation mode of the invention, and its purpose is to describe the basic spirit of the invention, but not to limit the invention. For the actual content of the invention, reference must be made to the scope of the claims that follow.

It must be understood that words such as "comprising" and "including" used in this specification are used to indicate the existence of specific technical features, values, method steps, operations, components and/or components, but do not exclude the possibility of adding More technical characteristics, numerical values, method steps, operation processes, components, components, or any combination of the above.

Words such as "first", "second", and "third" used in the claims are used to modify the elements in the claims, and are not used to indicate that there is a priority order, a pre-relationship, or an element An element preceding another element, or a chronological order in performing method steps, is only used to distinguish elements with the same name.

It should be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, intervening elements may be present. In contrast, when an element is described as being "directly connected" or "directly coupled" to another element, there are no intervening elements present. Other words used to describe the relationship between elements may be interpreted in a similar manner, such as "between" versus "directly between," or "adjacent" versus "directly adjacent," and so on.

FIG. 1 is a schematic diagram of an active noise canceling earphone according to a preferred embodiment of the present invention. Please refer to FIG. 1 , in this embodiment, a wireless earbud is taken as an example. Wireless earbuds are a pair of devices with wireless communication capabilities, including a left wireless earbud (left wireless earbud) 101 and a right wireless earbud (right wireless earbud) 102, and there is no entity between the left wireless earbud 101 and the right wireless earbud 102 The lines are connected to each other. Between the mobile device 103 and the left wireless earphone 101 and between the mobile device 103 and the right wireless earphone 102, a wireless communication protocol can be used to transmit voice packets or music packets carrying the user, such as the advanced audio distribution specification (advanced) of Bluetooth (Bluetooth). audio distribution profile, A2DP) packet.

In other embodiments, between the mobile device 103 and the left wireless earphone 101 and between the mobile device 103 and the right wireless earphone 102, other peer-to-peer (Wi-Fi Direct) and other peer-to-peer connections can also be used. -peer, P2P) wireless communication protocol, the present invention is not limited thereto.

In the above-mentioned embodiment, although the active noise canceling earphones are wireless earphones as an example, those skilled in the art should know that the active noise canceling earphones can also be implemented as wired earphones, and the present invention is not limited thereto.

FIG. 2 is a schematic diagram of an equivalent sampled-time (sampled-time) block diagram of an ANC earphone according to a preferred embodiment of the present invention. In this embodiment, the active noise reduction earphone is an earphone. Please refer to FIG. 2 , the ANC earphone includes an ANC integrated circuit 20 and an audio conversion device 21 . The audio conversion device 21 in this embodiment includes a first microphone 201 , a second microphone 202 and a speaker (not shown). In the embodiment of the present invention, for convenience of illustration, a dotted frame is taken as an example, and the earphone shell 19 is shown inside the dotted frame. Wherein, the first microphone 201 is outside the dotted line, indicating that the first microphone 201 is disposed outside the ear canal for receiving noise outside the ear canal, and the second microphone 202 is inside the dotted line, indicating that the second microphone 202 is disposed in the ear canal. In the following embodiments, the dotted line outline is used as a representation, but the dotted line is not used to limit the configuration of the components of the present invention.

The first microphone 201 is disposed outside the earphone housing 19 and is mainly used for receiving external noise signals of the earphone. The external noise signal picked up by the first microphone 201 is converted into an electrical signal and input to the active noise reduction integrated circuit 20 after, for example, orientation and analog-to-digital conversion. The first microphone 201 may be referred to as a reference microphone.

The second microphone 202 is arranged inside the earphone shell 19, and is located in the earphone shell 19 Between the eardrum and the eardrum, it is mainly used to receive the noise and echo in the user's ear canal, that is, the ear canal echo. The earphone housing 19 is used to provide passive noise cancellation. For example, the earphone housing 19 includes earphone sound-isolating material. More specifically, the second microphone 202 is used to receive sound signals in the user's ear canal. The audio signal captured by the second microphone 202 will be converted into an electrical signal and input to the second active noise cancellation filter unit 204 . The second microphone 202 may be referred to as an error microphone.

The active noise reduction integrated circuit 20 is used for generating an anti-noise electrical signal based on the electrical signal obtained through the first microphone 201 and the electrical signal obtained through the second microphone 202 . The anti-noise electrical signal in digital form is converted into an anti-noise signal through a digital-to-analog converter, a reconstruction filter, a power amplifier, and a speaker in sequence, for example. For analysis, the aforementioned transfers will be presented as transfer functions. In short, the anti-noise electrical signal is converted into an anti-noise signal through the aforementioned transfer function. Accordingly, in order to evaluate the transfer function of the aforementioned transmission, it is necessary to base on the anti-noise electrical signal and the anti-noise signal.

However, in practice, it is impossible to obtain the anti-noise signal directly. A possible alternative is to receive the anti-noise signal through the second microphone 202 in the absence of external noise signals, and convert the anti-noise signal into another electrical signal in analog form. The other electrical signal is converted into an electrical signal in digital form, for example, through a preamplifier, an anti-aliasing filter, and an analog-to-digital converter in sequence, and the electrical signal replaces the anti-noise signal to evaluate the transfer function.

Although the transfer function obtained in the alternative involves not only the transfer of the input of the ANC IC 20 to the second microphone 202, but also the transfer of the output of the second microphone 202 to the ANC IC 20, To simplify the analysis, the transfer function can be used to represent the transmission of the ANC IC 20 to the input of the second microphone 202 , which is represented by the physical channel 205 here. It should be noted that the physical channel 205 includes the above-mentioned speakers. In short, the anti-noise electrical signal output by the ANC IC 20 is converted into an anti-noise signal through the physical channel 205 .

On the other hand, the external noise signal enters the inner side of the earphone housing 19 from the outer side of the earphone housing 19 , and finally reaches the second microphone 202 . This transmission is the primary path, not shown. For analysis, the main paths will be presented as transfer functions. In short, the external noise signal is transformed into the residual noise signal through the transfer function of the main path. Accordingly, to evaluate the transfer function of the main path, it needs to be based on the external noise signal and the residual noise signal.

However, in practice, it is impossible to directly obtain the external noise signal and the residual noise signal. A possible alternative is to receive an external noise signal through the first microphone 201 and convert the external noise signal into another electrical signal in analog form. The other electric signal is converted into a digital electric signal through the preamplifier, the anti-aliasing filter and the analog-to-digital converter in sequence, and the electric signal replaces the external noise signal to evaluate the transfer function of the main path. On the other hand, the residual noise signal is received by the second microphone 202 under the condition that the ANC IC 20 is disabled, and the residual noise signal is converted into another electrical signal in an analog form. The other electrical signal is converted into a digital electrical signal by, for example, a preamplifier, an anti-aliasing filter, and an analog-to-digital converter in sequence. The electrical signal replaces the residual noise signal to evaluate the transfer function of the main path.

When the ANC earphone is actually in operation (that is, when the ANC integrated circuit 20 is enabled), the anti-noise signal interferes with the residual noise signal to achieve the effect of ANC.

The ANC IC 20 includes a first path and a second path.

The first path receives the output signal from the first microphone 201 and outputs a first path anti-noise signal to the physical channel 205 . The anti-noise signal of the first path is converted by the physical channel 205 into a first signal for noise cancellation.

The second path receives the output signal from the second microphone 202 and outputs a second path anti-noise signal to the physical channel 205 . The anti-noise signal of the second path is converted by the physical channel 205 into a second signal for noise cancellation.

The first path includes a first active noise cancellation filtering unit 203 . Further, the first path starts from the output end of the first microphone 201 , passes through the first active noise cancellation filtering unit 203 , and reaches the input end of the physical channel 205 .

The second path includes a second active noise cancellation filtering unit 204 . Further, the second path starts from the output end of the second microphone 202 , passes through the second active noise cancellation filtering unit 204 , and reaches the input end of the physical channel 205 .

In the embodiment in FIG. 2 , the first active noise cancellation filter unit 203 filters the electrical signal output by the first microphone 201 to generate a first anti-noise signal y ' ₁ ( n ). The first anti-noise signal y'1 (n ₎ is used as the first path anti-noise signal in this embodiment. The weight of the first active noise cancellation filtering unit 203 is marked as W ₁ in FIG. 2 . The first active noise cancellation filtering unit 203 can be implemented in various ways, such as using general-purpose hardware (for example, a microcontroller unit, a digital signal processor, a single processor, a multi-processor with parallel processing capabilities, a graphics processor, or other computing power), and provide an active noise cancellation filtering function when executing software and/or firmware instructions.

The second active noise cancellation filter unit 204 filters the electrical signal output by the second microphone 202 to generate a second anti-noise signal y ′ ₂ ( n ). A second anti-noise signal y ′ ₂ ( n ) is used as the second path anti-noise signal in this embodiment. The weight of the second active noise cancellation filtering unit 204 is marked as W ₂ in FIG. 2 . The second active noise cancellation filtering unit 204 can be implemented in various ways, such as using general-purpose hardware (for example, a microcontroller unit, a digital signal processor, a single processor, a multi-processor with parallel processing capabilities, a graphics processor, or other computing power), and provide an active noise cancellation filtering function when executing software and/or firmware instructions.

In this embodiment, the first anti-noise signal y ′ ₁ ( n ) and the second anti-noise signal y ′ ₂ ( n ) are input to the physical channel 205 respectively. However, the present disclosure is not limited thereto. In some embodiments, the first anti-noise signal y ′ ₁ ( n ) and the second anti-noise signal y ′ ₂ ( n ) can be added in the digital domain, and the summed anti-noise signal is input to the physical channel 205 .

The audio conversion device 21 converts the first anti-noise signal y'1 ( _n ) and the second anti-noise signal y'2 ( _n ) into audio signals through the physical channel 205 , and synthesizes them into a noise-cancellation signal (that is, the aforementioned anti-noise signal). When the noise canceling signal is actually transmitted through the ear canal, echo interference will be generated due to the reflection and attenuation of sound waves in the ear canal. In other words, the noise cancellation signal will reach the user's ear and the second microphone 202 through a physical channel of the real environment.

In this embodiment, the stackable multiple active noise reduction integrated circuit 20 has, for example, a dual anti-noise system, that is, two active noise cancellation filter units 203 and 204 , which can output two noise cancellation signals correspondingly. Interference between the two noise canceling signals is generally expected to achieve further noise suppression. However, this is not the case in practice, as detailed in Figure 3. Please refer to Figure 3, which is a comparison chart of the noise suppression results of the embodiment in Figure 2.

As shown in FIG. 3 , the vertical axis represents magnitude and the horizontal axis represents frequency. The reference number 301 indicates noise; the reference number 302 indicates the noise suppression result of only opening the first active noise cancellation filtering unit 203 (feed forward, FF); the label 303 indicates only opening the second active noise cancellation filtering unit 204 (feedback, FB) Noise suppression results; reference numeral 304 indicates the expected noise suppression result of turning on the first active noise cancellation filter unit 203 and the second active noise cancellation filter unit 204 (FF+FB); and label 305 indicates that the first active noise cancellation filter unit is turned on 203 and the real noise suppression result of the second active noise cancellation filtering unit 204 (FF+FB). Comparing reference numerals 304 and 305, it can be observed that reference numerals 304 and 305 overlap at relatively low frequencies, but do not overlap at relatively high frequencies. That is to say, at relatively high frequencies, the real noise suppression results cannot reach the expected noise suppression results.

In order to explain why there is such a result, refer back to Figure 2, d ( n ) represents the main noise signal from the external noise signal, that is, the aforementioned residual noise signal; y ₁ ( n ) represents the relative first active noise Eliminate the first signal of the first anti-noise signal y ' ₁ ( n ) output by the filter unit 203, the first signal y ₁ ( n ) is a sound signal; y ₂ ( n ) represents the filter related to the second active noise cancellation The second signal of the second anti-noise signal y ′ ₂ ( n ) output by the unit 204, the second signal y ₂ ( n ) is an audio signal; and, e ( n ) represents the error signal output by the second microphone 202. It should be noted that, in order to simplify the description, the process of converting the audio signal into a digital electrical signal is omitted.

The error signal e ( n ) output by the second microphone 202 can be regarded as an electrical signal in digital form.

When no active noise cancellation filter units 203 and 204 are turned on, the second microphone 202 only captures the main noise signal d ( n ) as the error signal e ( n ), that is, e ( n )= d ( n ). When the second active noise cancellation filter unit 204 is turned on, the second microphone 202 captures the main noise signal d ( n ) and the second signal y2 ( _n ) as the error signal e ( n ), that is, e ( n ) = d ( n ) + y ₂ ( n ). The main noise signal d ( n ) and the second signal y ₂ ( n ) are summed through the adding unit 206 . It should be noted that the adding unit 206 shown in the figure is not a physical component, but is only for easy understanding in analysis. Similarly, when the active noise cancellation filter units 203 _and 204 are turned on, the second microphone 202 captures the main noise signal d ( n ), the first signal y1 ( n ) and the second signal y2 ₍ n ) for is the error signal e ( n ), that is , e ( n ) = d ( n ) + y ₁ ( n ) + y ₂ ( n ).

The second active noise cancellation filtering unit 204 generates a second anti-noise signal y ′ ₂ ( n ) based on the error signal e ( n ) received by the second microphone 202. However, in this case, based on the formula e ( n ) = d ( n ) + y ₁ ( n ) + y ₂ ( n ), it can be seen that the error signal e ( n ) captured by the second microphone 202 has been affected by the first The interference of a signal y ₁ ( n ) makes the second anti-noise signal y ′ ₂ ( n ) generated by the second active noise cancellation filter unit 204 ineffective, which leads to problems such as over-processing of noise. In short, every time the sound received by the second microphone 202 contains the first signal y ₁ ( n ), the actual noise cannot be properly suppressed or over-compensated.

The earphone type in the above-mentioned embodiment is an earphone, that is to say, the earphone shell 19 is considered to be able to effectively block the second signal y ₂ ( n ) from propagating to the outside of the earphone, so that the first microphone 201 cannot receive it. The second signal y ₂ ( n ). If the earphone is open and the earphone shell 19 is deemed unable to effectively block the second signal y ₂ ( n ) from being transmitted to the outside of the earphone, the first microphone 201 will receive the second signal y ₂ ( n ), which will cause mutual Interference is more serious, which in turn may cause noise to be more serious than if there was only a single noise reduction system.

In order to solve the above-mentioned problems, one possible way is to remove the first signal y ₁ ( n ) from the error signal e ( n ) based on the mathematical principle of linear systems, such as the embodiment in FIG. 4 of this application.

FIG. 4 is a schematic block diagram of an equivalent sampling time of an ANC earphone with good isolation according to a preferred embodiment of the present invention. The active noise reduction headphones in Figure 4 use a composite noise reduction architecture. Referring to Fig. 4, the active noise-cancelling earphone in Fig. 4 is similar to the active noise-cancelling earphone in Fig. 2, the difference is that the stackable multiple active noise-cancelling integrated circuit 20 in Fig. 4 further includes a first decoupling Unit 40. The first decoupling unit 40 is used for removing the first signal y ₁ ( n ) in the error signal e ( n ) captured by the second microphone 202 by electrical signal processing. In some embodiments, the first decoupling unit 40 is implemented by a digital signal processor. In this embodiment, the first path starts from the output end of the first microphone 201, passes through the first active noise cancellation filter unit 203, and reaches the input end of the physical channel 205; and, the second path starts from the output end of the second microphone 202 , to the input end of the physical channel 205 via the second active noise cancellation filter unit 204 .

。換言之，模擬的物理通道

實質上相同於物理通道S(z)205。 The first decoupling unit 40 includes a first channel analog filter 401 and a first adding circuit 402 . The first channel analog filter 401 is, for example, the transfer function of the simulated physical channel 205, and the simulated physical channel is represented by the Z domain transfer function as

. In other words, the simulated physical channel

It is substantially the same as the physical channel S ( z ) 205 .

The physical channel 205 is used to represent the transmission of the ANC filter (such as the first active noise cancellation filter unit 203 or the second active noise cancellation filter unit 204) to the second microphone 202, so as to analyze the electrical signal output by the ANC filter when passing through the The transformation after transmission is described, where the simulation result is represented by the transfer function S ( z ). In some possible implementations, the external noise source is removed, and the transfer function S ( z ) is estimated based on the electrical signal output by the ANC filter and based on the error signal e (n) obtained through the second microphone 202, where Since there is no external noise source, there is no main noise signal d ( n ). Therefore, the error signal e (n) is substantially the same as at least one of the first signal y ₁ ( n ) and the second signal y ₂ ( n ) or the sum thereof, depending on the first active noise cancellation filter unit 203 and the second active noise canceling filter unit 203 The activation of the noise cancellation filter unit 204 depends.

。在模擬的物理通道

實質上相同於物理通道S(z)205的情況下，由於模擬的物理通道

及物理通道S(z)205的輸入訊號均為第一抗噪訊號y'₁(n)，模擬的物理通道

所輸出的第一解耦合訊號

實質上等效於物理通道S(z)205所輸出的第一訊號y ₁(n)。接著，第一加法電路402的第一輸入埠接收第一解耦合訊號

，第一加法電路402的第二輸入埠接收誤差訊號e(n)。接著，第一加法電路402將誤差訊號e(n)中的第一解耦合訊號

的成份扣除(視為扣除第一訊號y ₁(n))，並提供給第二主動噪音消除濾波單元204。第二主動噪音消除濾波單元204所接收到的誤差訊號e(n)便實質上等於d(n)+y ₂(n)，不再含有第一訊號y ₁(n)。因此，雜訊抑制效果會顯著的提昇。本實施例藉由第一解耦合單元40在電路的訊號處理中，將誤差訊號e(n)的第一訊號y ₁(n)扣除，以解決上述過度補償的問題。 The first channel analog filter 401 receives the first anti-noise signal y ' ₁ ( n ) output by the first active noise cancellation filter unit 203 to generate a first decoupling signal

. in the simulated physical channel

is substantially the same as the case of physical channel S ( z )205, since the simulated physical channel

and the input signal of the physical channel S ( z ) 205 are the first anti-noise signal y ' ₁ ( n ), the simulated physical channel

The output of the first decoupling signal

It is substantially equivalent to the first signal y ₁ ( n ) output by the physical channel S ( z ) 205. Next, the first input port of the first adding circuit 402 receives the first decoupling signal

, the second input port of the first adding circuit 402 receives the error signal e ( n ). Next, the first adding circuit 402 takes the first decoupled signal in the error signal e ( n )

The component of is subtracted (deemed as subtracting the first signal y ₁ ( n )), and provided to the second active noise cancellation filter unit 204 . The error signal e ( n ) received by the second active noise cancellation filter unit 204 is substantially equal to d ( n )+ y ₂ ( n ), and does not contain the first signal y ₁ ( n ). Therefore, the noise suppression effect will be significantly improved. In this embodiment, the first decoupling unit 40 subtracts the first signal y ₁ ( n ) from the error signal e ( n ) in the signal processing of the circuit, so as to solve the above-mentioned overcompensation problem.

FIG. 5 is a schematic block diagram of an equivalent sampling time of an ANC earphone with good isolation according to a preferred embodiment of the present invention. The active noise reduction headphones in Figure 5 use a composite noise reduction architecture. Please refer to FIG. 2 and FIG. 5. In this embodiment, a first decoupling unit 50 is additionally added to the stackable multiple active noise reduction integrated circuits 20 to convert the first signal y ₁ ( n ) are removed by electrical signal processing.

In this embodiment, the first decoupling unit 50 includes a first channel analog filter 501 , a third active noise cancellation filter unit 502 , a first adding circuit 503 and a second adding circuit 504 .

，其中，第一抗噪訊號y'₁(n)為由第一麥克風201所接收的外部噪音訊號，並經過取樣數位/類比轉換之後，透過第一主動噪音消除濾波單元203之運算獲得。 The function of the first channel analog filter 501 is the same as that of the first channel analog filter 401 in the embodiment shown in FIG. 4 . The first channel analog filter 501 is used to simulate the physical channel 205, and receives the first anti-noise signal y ' ₁ ( n ) to generate the first decoupling signal

, wherein the first anti-noise signal y ' ₁ ( n ) is the external noise signal received by the first microphone 201 , and is obtained through the operation of the first active noise cancellation filter unit 203 after sampling digital/analog conversion.

輸入進第三主動噪音消除濾波單元502時，第三主動噪音消除濾波單元502所輸出的第三抗噪訊號可表示為

。 In this embodiment, the transfer function of the third active noise cancellation filtering unit 502 is, for example, the same as the transfer function of the second active noise cancellation filtering unit 204 , so the weight of the third active noise cancellation filtering unit 502 is also W ₂ . That is to say, the filtering operation of the third active noise cancellation filtering unit 502 is the same as the filtering operation of the second active noise cancellation filtering unit 204 . Therefore, when the first decoupled signal

When input into the third active noise cancellation filter unit 502, the third anti-noise signal output by the third active noise cancellation filter unit 502 can be expressed as

.

The second active noise cancellation filtering unit 204 receives the error signal output by the second microphone 202, marked as d ( n )+ y ₁ ( n )+ y ₂ ( n ), so the output of the second active noise cancellation filtering unit 204 The signal of is denoted as [ d ( n ) + y ₁ ( n ) + y ₂ ( n )] W ₂ .

，第一加法電路503的第二輸入埠接收第二抗噪訊號〔d(n)+y ₁(n)+y ₂(n)〕W ₂。由於

實質上等效於y ₁(n)，因此，第一加法電路503將兩訊號相減之後，輸出近似為〔d(n)+y ₂(n)〕W ₂。此〔d(n)+y ₂(n)〕W ₂即去除了y ₁(n)的成份。又，該輸出〔d(n)+y ₂(n)〕W ₂中的主噪音訊號d(n)可忽略不計。因此，該輸出〔d(n)+y ₂(n)〕W ₂可進一步簡化為式子〔y ₂(n)〕W ₂，其在此表示為y'₂(n)。由此可知，雖然第二主動噪音消除濾波單元204受到第一訊號y ₁(n)的干擾，但該干 擾通過第三主動噪音消除濾波單元502及第一加法電路503被等效地消除了。 The first input port of the first adding circuit 503 receives the third anti-noise signal

, the second input port of the first adding circuit 503 receives the second anti-noise signal [ d ( n ) + y ₁ ( n ) + y ₂ ( n )] W ₂ . because

It is substantially equivalent to y ₁ ( n ), therefore, after the first adding circuit 503 subtracts the two signals, the output is approximately [ d ( n )+ y ₂ ( n )] W ₂ . This [ d ( n ) + y ₂ ( n ) ] W ₂ has removed the component of y ₁ ( n ). Also, the main noise signal d ( n ) in the output [ d ( n ) + y ₂ ( n )] W ₂ can be neglected. Therefore, the output [ d ( n ) + y ₂ ( n )] W ₂ can be further simplified into the formula [ y ₂ ( n )] W ₂ , which is denoted here as y ′ ₂ ( n ). It can be seen that although the second active noise cancellation filtering unit 204 is interfered by the first signal y ₁ ( n ), the interference is equivalently eliminated by the third active noise cancellation filtering unit 502 and the first adding circuit 503 .

The first input port of the second adding circuit 504 is coupled to the output port of the first adding circuit 503 to receive the output y'2 ( n ), _and the second input port _of the second adding circuit 504 receives the first anti-noise signal y'1 ( n ), adding the two signals to obtain the electrical signal component y ' ₁ ( n ) + y ' ₂ ( n ) of the noise cancellation signal. In some embodiments, the second summing circuit 504 may be omitted.

The above-mentioned embodiment in FIG. 5 adopts a decoupling method different from that in FIG. 4 , but it can also eliminate redundant components of the first signal y ₁ ( n ). Another embodiment is proposed below, which can also eliminate redundant components of the first signal y ₁ ( n ), so that those skilled in the art can implement the present invention accordingly.

FIG. 6 is a schematic block diagram of an equivalent sampling time of an ANC earphone with good isolation according to a preferred embodiment of the present invention. The active noise-canceling headphones in Figure 6 use a composite noise-canceling architecture. Different from the embodiment in FIG. 5, the error signal e ( n ) provided by the second microphone 202 is processed to achieve the decoupling effect. In the embodiment in FIG. 6, the signal provided by the first microphone 201 is processed To achieve the effect of decoupling, the details are as follows.

The first decoupling unit 60 includes a third active noise cancellation filter unit 601, a channel analog filter 602, a first adding circuit 603 and a second adding circuit 604, wherein the function of the channel analog filter 602 is the same as that of the fourth The first channel analog filter 401 of the embodiment of the figure.

。 The operation of the third active noise cancellation filtering unit 601 is the same as that of the second active noise cancellation filtering unit 204, the difference is that the third active noise cancellation filtering unit 601 receives the output from the first active noise cancellation filtering unit 203 the first anti-noise signal y ' ₁ ( n ), and output the third anti-noise signal y ' ₁ ( n ) W ₂ . After that, it is processed by the first channel analog filter 602 to generate the first decoupled signal

.

In addition, the operation of the third active noise cancellation filtering unit 601 is similar to the third active noise cancellation filtering unit 502 in FIG. 5, the difference is that in the embodiment in _FIG . After being processed by the first channel analog filter 501, and then processed by the third active noise cancellation filter unit 502, and in this embodiment, the first anti-noise signal y ' ₁ ( n ) first passes through the third active noise cancellation filter unit 601 processing, and then processed by the channel analog filter 602. According to the mathematical principle of the linear system, the above-mentioned difference in the arrangement order does not substantially change the result, which will not be repeated here. Accordingly, in some embodiments, it can be configured that the first anti-noise signal y ′ ₁ ( n ) is firstly processed by the channel analog filter 602, and then processed by the third active noise cancellation filter unit 601.

，第一加法電路603的第二輸入埠接收第一抗噪訊號y'₁(n)，並將兩者相減，之後透過第二加法電路604將第二主動噪音消除濾波單元204路徑上的訊號進行互相干涉，以消除第二主動噪音消除濾波單元204輸出的抗噪訊號〔d(n)+y ₁(n)+y ₂(n)〕W ₂中多餘的第一訊號y ₁(n)成份。明確來說，第一加法電路603輸出的訊號[y'₁(n)-

]中的成分

用來消除第二主動噪音消除濾波單元204輸出的抗噪訊號〔d(n)+y ₁(n)+y ₂(n)〕W ₂中的成分[y ₁(n)W ₂]。又，抗噪訊號〔d(n)+y ₁(n)+y ₂(n)〕W ₂中的主噪音訊號d(n)可忽略不計。據此，第二加法電路604輸出的訊號為[y ₂(n)W ₂+y'₁(n)]，其進一步簡化為[y'₂(n)+y'₁(n)]。 The first input port of the first adding circuit 603 receives the first decoupling signal

, the second input port of the first addition circuit 603 receives the first anti-noise signal y ' ₁ ( n ), and subtracts the two, and then passes through the second addition circuit 604 the second active noise cancellation filter unit 204 path The signals interfere with each other to eliminate the redundant first signal y 1 ₍ n ) in the anti-noise signal [ d ( n ) + y ₁ ( n ) + y ₂ ( n )] W ₂ output by the second active noise cancellation filter unit 204 ) ingredients. Specifically, the signal output by the first adding circuit 603 [ y ' ₁ ( n )-

] ingredients in

It is used to eliminate the component [ y ₁ (n) W ₂ ] in the anti-noise signal [ d ( n )+ y ₁ ( n )+ y ₂ ( n )] W ₂ output by the second active noise cancellation filtering unit 204. Also, the main noise signal d ( n ) in the anti-noise signal [ d ( n ) + y ₁ ( n ) + y ₂ ( n )] W ₂ can be ignored. Accordingly, the output signal of the second adding circuit 604 is [ y ₂ ( n ) W ₂ + y ′ ₁ ( n )], which is further simplified to [ y ′ ₂ ( n )+ y ′ ₁ ( n )].

In the above-mentioned embodiments, earphones are taken as examples. Since the earphone has a good isolation effect between the internal microphone and the external microphone, the noise received by the internal microphone cannot be received by the external microphone. Therefore, in the above embodiment, the echo noise cannot affect the first microphone. Here is an example of not having good isolation.

FIG. 7 is a schematic block diagram of an equivalent sampling time of an ANC headphone without good isolation according to a preferred embodiment of the present invention. The active noise reduction headphones in Figure 7 use a composite noise reduction architecture. Please refer to FIG. 7, in this embodiment, the ANC earphone is semi-in-ear. The ear of active noise canceling headphones of this type The case 19 cannot effectively block the transmission of sound from the inside of the ANC earphone to the outside of the ANC earphone, so the reverse noise of the echo inside the ear canal will also interfere with the external first microphone 201 . Therefore, in addition to the first decoupling unit 40 , the stackable multiple active noise reduction device of the above active noise canceling earphone system further includes a second decoupling unit 70 .

The concept of this technique is the same as that of the above-mentioned several embodiments. The first decoupling unit 40 is used for generating a first decoupling signal according to the anti-noise signal output by the first active noise cancellation filter unit 203 . Likewise, the second decoupling unit 70 is used for generating a second decoupling signal according to the anti-noise signal output by the second active noise cancellation filter unit 204 .

，此第一解耦合訊號

實質上幾乎等於第一訊號y ₁(n)。第二麥克風202所接收的第一誤差訊號e ₂(n)為[d ₂(n)+y ₁(n)+y ₂(n)]。接著，第一加法電路402的第一輸入埠接收第一解耦合訊號

，第一加法電路402的第二輸入埠接收第一誤差訊號e ₂(n)。藉此，第一解耦合訊號

將第一誤差訊號e ₂(n)的y ₁(n)成份扣除，並輸出給第二主動噪音消除濾波單元204，第二主動噪音消除濾波單元204所接收到的訊號e ₂’(n)便實質上等於d ₂(n)+y ₂(n)。換言之，第二主動噪音消除濾波單元204不再受到第一訊號y ₁(n)的干擾，而能夠產生有效的抗噪訊號。為了方便說明第7圖的實施例中，物理通道205的轉移函數表示為S ₁(z)，第一通道模擬濾波器401的轉移函數表示為

。 In this embodiment, the first decoupling unit 40 is similar to the embodiment in FIG. 4 , including a first channel analog filter 401 and a first adding circuit 402 . The first channel analog filter 401 is substantially the same as the physical channel 205, and it receives the first anti-noise signal y ' ₁ ( n ) output by the first active noise cancellation filter unit 203 to generate the first decoupling signal

, this first decoupled signal

It is substantially equal to the first signal y ₁ ( n ). The first error signal e ₂ ( n ) received by the second microphone 202 is [ d ₂ ( n )+ y ₁ ( n )+ y ₂ ( n )]. Next, the first input port of the first adding circuit 402 receives the first decoupling signal

, the second input port of the first adding circuit 402 receives the first error signal e ₂ ( n ). Thereby, the first decoupled signal

The y ₁ ( n ) component of the first error signal e ₂ ( n ) is subtracted and output to the second active noise cancellation filter unit 204, the signal e ₂ '( n ) received by the second active noise cancellation filter unit 204 It is essentially equal to d ₂ ( n ) + y ₂ ( n ). In other words, the second active noise cancellation filter unit 204 is no longer interfered by the first signal y ₁ ( n ), and can generate an effective anti-noise signal. In order to facilitate the description in the embodiment of Fig. 7, the transfer function of the physical channel 205 is expressed as S ₁ ( z ), and the transfer function of the first channel analog filter 401 is expressed as

.

On the other hand, since the mechanism appearance of the earphone in this embodiment is not isolated, the reverse noise of the echo inside the ear canal will also interfere with the external first microphone 201, and the other physical channel 72 of this real environment is also Expressed as S ₂ ( z ) in the Z domain transfer function. In other words, the transfer function S ₂ ( z ) of the second physical channel 72 is used to represent the transfer between the ANC IC 20 and the input of the first microphone 201 . Similarly, after the anti-noise signals y ' ₁ ( n ) and y ' ₂ ( n ) output by stackable multiple active noise reduction integrated circuits 20 are transmitted through the second physical channel 72, x ₁ ( n ) represents the An audio signal corresponding to an anti-noise signal y'1 ( n ), _{and x2} ( n ) represents an audio signal corresponding to a _second anti-noise signal y'2 ( _n ) . In terms of actual audio signal transmission, since the signals x ₁ ( n ) and x ₂ ( n ) are transmitted from the ear canal to the first microphone 201 , their channel responses are different from those in the ear canal. Therefore, the signals x ₁ ( n ) and x ₂ ( n ) are different from the sound signals y ₁ ( n ) and y ₂ ( n ).

In addition to receiving the signals x ₁ ( n ) and x ₂ ( n ), the first microphone 201 also receives the external noise signal d ₁ ( n ), accordingly, the first microphone 201 converts the external noise signal d ₁ ( n ), the signal x ₁ ( n ) and x ₂ ( n ) serve as the second error signal e ₁ ( n ). In addition, the external noise signal d ₁ ( n ) enters the outside of the active noise canceling earphone and is converted into the main noise signal d ₂ ( n ) . The main noise signal d ₂ ( n ) is substantially equal to the main Noise signal d ( n ).

If the second error signal e ₁ ( n ) is not processed, and the first active noise cancellation filter unit 203 receives the second error signal e ₁ ( n ) including the signal x ₂ ( n ), similar to the embodiment in FIG. 2 For reasons of illustration, the first active noise cancellation filtering unit 203 is interfered by the signal x ₂ ( n ), and thus the generated anti-noise signal cannot effectively cancel the noise. Therefore, the signal x ₂ ( n ) needs to be removed from the second error signal e ₁ ( n ), so that the signal received by the first active noise cancellation filter unit 203 does not contain the signal x ₂ ( n ).

Therefore, this embodiment proposes a second decoupling unit 70 including a second channel analog filter 701 and a second adding circuit 702 . Since the signal x ₂ ( n ) is output by the physical channel 72, in order to effectively eliminate the signal x ₂ ( n ) in the second error signal e ₁ ( n ), the second channel analog filter 701 needs to simulate the above physical channel 72 instead of emulating physical channel 205.

。此第二解耦合訊號

實質上幾乎等於訊號x ₂(n)。接著，第二加法電路 702的第一輸入埠接收第二解耦合訊號

，第二加法電路702的第二輸入埠接收第二誤差訊號e ₁(n)。藉此，將第二誤差訊號e ₁(n)中的訊號x ₂(n)成份扣除，並輸出給第一主動噪音消除濾波單元203。第一主動噪音消除濾波單元203所接收到的訊號e ₁’(n)便實質上等於d ₁(n)+x ₁(n)，第一主動噪音消除濾波單元203不會受到訊號x ₂(n)的干擾，因而產生的第一抗噪訊號y'₁(n)是有效的。 The second channel analog filter 701 receives the second anti-noise signal y ' ₂ ( n ) output by the second active noise cancellation filter unit 204 to generate a second decoupling signal

. This second decoupling signal

In essence, it is almost equal to the signal x ₂ ( n ). Next, the first input port of the second adding circuit 702 receives the second decoupling signal

, the second input port of the second adding circuit 702 receives the second error signal e ₁ ( n ). Thereby, the signal x ₂ ( n ) component in the second error signal e ₁ ( n ) is subtracted and output to the first active noise cancellation filter unit 203 . The signal e ₁ '( n ) received by the first active noise cancellation filter unit 203 is substantially equal to d ₁ ( n )+ x ₁ ( n ), and the first active noise cancellation filter unit 203 will not receive the signal x ₂ ( n ), the resulting first anti-noise signal y ' ₁ ( n ) is effective.

In this embodiment, the first path starts from the output end of the first microphone 201 , passes through the first active noise cancellation filtering unit 203 , and reaches the input ends of the physical channels 205 and 72 . The second path starts from the output of the second microphone 202 , through the second ANC filter unit 204 , to the input of the physical channels 205 and 72 . The anti-noise signal of the first path is converted into the third signal x ₁ ( n ) by the second physical channel 72 . The anti-noise signal of the second path is converted into a fourth signal x ₂ ( n ) by the second physical channel 72 . In other words, the first path receives the second error signal e ₁ ( n ) containing the component of the fourth signal x ₂ ( n ), so that the first active noise cancellation filtering unit 203 in the first path receives the fourth signal x ₂ ( n ) Interference. The second decoupling unit 70 in this embodiment removes the component of the fourth signal x ₂ ( n ) in the first path based on the second anti-noise signal y ′ ₂ ( n ).

In other embodiments, only a single microphone is implemented, but there are examples of dual anti-noise systems. As shown in FIG. 8, FIG. 8 is a schematic block diagram of an equivalent sampling time of an ANC earphone according to a preferred embodiment of the present invention. The embodiment of the active noise reduction earphone in Fig. 8 adopts a feedback noise reduction architecture. Please refer to Fig. 8, in this embodiment, there is only the second microphone 202 (noise receiving microphone in the ear canal), however, in this embodiment, there is indeed a first active noise cancellation filter unit 203 and a second active Noise elimination filtering unit 204 .

。同樣地，第二加法電路802接收第二解耦合訊號

與誤差訊號e(n)，並將誤差訊號e(n)中的訊號y ₂(n)成份扣除，輸出給第一主動噪音消除濾波單元203。第一主動噪音消除濾波單元203所接收到的訊號e ₁’(n)便實質上等於d(n)+y ₁(n)，使得第一主動噪音消除濾波單元203不會受到訊號y ₂(n)的干擾，因而產生有效噪的第一抗噪訊號y'₁(n)。 Different from the embodiment in FIG. 7, if the signal received by the first active noise cancellation filtering unit 203 has not been decoupled, that is, the error signal e ( n ) without decoupling processing is directly received, the first active noise cancellation filter Unit 203 will be disturbed by the second signal y ₂ ( n ) instead of the signal x ₂ ( n ) in the embodiment of FIG. 7 . Therefore, in order to effectively eliminate the signal y ₂ ( n ) in the error signal e ( n ), the channel analog filter 801 in the second decoupling unit 80 needs to simulate the above-mentioned physical channel 205 instead of simulating the physical channel 72, so as to generate the first Two decoupling signals

. Similarly, the second adding circuit 802 receives the second decoupling signal

and the error signal e ( n ), subtract the signal y ₂ ( n ) component from the error signal e ( n ), and output it to the first active noise cancellation filter unit 203 . The signal e ₁ ′( n ) received by the first active noise cancellation filter unit 203 is substantially equal to d ( n )+ y ₁ ( n ), so that the first active noise cancellation filter unit 203 will not receive the signal y ₂ ( n ), thus producing the first anti-noise signal y ' ₁ ( n ) of effective noise.

That is to say, please refer to FIG. 7 and FIG. 8 , the embodiments in FIG. 7 and FIG. 8 adopt almost the same cancellation architecture, and the only difference is that FIG. 8 only has the second microphone 202 . Since the method for eliminating redundant components is similar, it will not be repeated here.

In this embodiment, the first path starts from the output end of the second microphone 202 , passes through the first active noise cancellation filtering unit 203 , and reaches the input end of the physical channel 205 . The second path starts from the output of the second microphone 202 , via the second active noise cancellation filter unit 204 , to the input of the physical channel 205 .

FIG. 9 is a schematic block diagram of an equivalent sampling time of an ANC earphone with good isolation according to a preferred embodiment of the present invention. The active noise reduction headphones in Figure 9 use a composite noise reduction architecture. Please refer to FIG. 9 and FIG. 8 first. The difference between FIG. 9 and FIG. 8 is that additional feed-forward noise reduction is added, that is, the first microphone 201 and the third active noise cancellation filter unit 91 are added.

For the first active noise cancellation filtering unit 203, if the signal received by the first active noise cancellation filtering unit 203 has not been decoupled, the first active noise cancellation filtering unit 203 will receive the signals y ₀ ( n ) and y ₂ ( n ) interference. Therefore, the channel analog filter 901 and the adding circuit 902 in the third decoupling unit 90 are used to eliminate the interference of the signal y ₀ ( n ), and the second decoupling unit 80 is used to eliminate the interference of the signal y ₂ ( n ). The principle of eliminating interference is the same as that of the foregoing embodiments, and will not be repeated here.

For the second active noise cancellation filtering unit 204, if the signal received by the second active noise cancellation filtering unit 204 has not been decoupled, the second active noise cancellation filtering unit 204 will receive the signals y ₀ ( n ) and y ₁ ( n ) interference. Therefore, the channel analog filter 901 and the adding circuit 903 in the third decoupling unit 90 are used to eliminate the interference of the signal y ₀ ( n ), and the first decoupling unit 40 is used to eliminate the interference of the signal y ₁ ( n ). The principle of eliminating interference is the same as that of the foregoing embodiments, and will not be repeated here. In addition, in this embodiment, in order to simplify the wiring complexity in the schematic diagram of the components, the relative position drawn between the adding unit 206 and the second microphone 202 in Figure 9 is the same as the position of the adding unit 206 and the second microphone 202 in Figure 8 However, those skilled in the art can infer that the relative positions of the adding unit 206 and the second microphone 202 in the figure cannot be used to limit the component configuration of the present invention.

It can be seen from the above description that this embodiment further includes a third path, the third path starts from the output end of the first microphone 201 , passes through the third active noise cancellation filtering unit 91 , and reaches the input end of the physical channel 205 . The third anti-noise signal y ' ₀ ( n ) output by the third active noise cancellation filter unit 91 is, for example, the third path anti-noise signal in this embodiment, and the third anti-noise signal y ' ₀ ( n ) is passed through a physical The channel 205 is converted into the third signal y ₀ ( n ). Since both the first path and the second path receive the error signal e ( n ) containing the component of the third signal y ₀ ( n ). Therefore, the third decoupling unit 90 proposed in this embodiment removes the components of the third signal y ₀ ( n ) in the first path and the second path based on the third anti-noise signal y ′ ₀ ( n ).

In order to solve the above-mentioned problems, an embodiment of the present invention proposes a stackable multiple active noise reduction method. FIG. 10 is a flow chart of a stackable multiple active noise reduction method according to a preferred embodiment of the present invention. Please refer to Figure 10, this stackable multiple active noise reduction method includes the following steps:

Step S1001: Provide a first path, output a first path anti-noise signal, wherein the first path anti-noise signal is converted into a first signal by a physical channel, the first path includes: a first active noise elimination filter unit , for generating a first anti-noise signal; providing a second path for receiving an error signal containing components of the first signal, And output a second path anti-noise signal to the physical channel, the second path includes: a second active noise cancellation filter unit for generating a second anti-noise signal, wherein the second anti-noise signal derives the second path anti-noise signal.

Step S1002: Remove components of the first signal in the second path based on the first anti-noise signal. As shown in FIG. 4, by passing the first anti-noise signal through the first channel analog filter 401, at the input end of the second active noise cancellation filter unit, the second active noise cancellation filter unit 204 receives the The component of the first signal y ₁ ( n ) in the error signal e ( n ) is removed. Moreover, as shown in FIG. 5, by passing the first anti-noise signal through the first channel analog filter 501 and the third active noise cancellation filter unit 502 (the transfer function of this unit and the second active noise cancellation filter unit same), generate a decoupling signal, and perform decoupling at the output end of the second active noise cancellation filtering unit 204 . Similarly, as shown in FIG. 6, by passing the first anti-noise signal through the sound channel analog filter 602 and the third active noise cancellation filter unit 601 (this unit has the same transfer function as the second active noise cancellation filter unit ), generate a decoupling signal, and perform decoupling after the output of the second active noise cancellation filtering unit 204 . In other words, as long as there are at least two ANC filter units, and the anti-noise signals generated by the above-mentioned ANC filter units are mutually coupled, the decoupling signal can be generated by using one of the specific anti-noise signals, Eliminate the components of specific anti-noise signals in the path of other active noise cancellation filter units. In this way, the present invention can eliminate the aforementioned mutual interference. The above-mentioned embodiments of the 7th, 8th and 9th figures are the embodiments derived from this spirit. Therefore, the present invention is not limited to Figures 4, 5, and 6.

Step S1003: Play based on the anti-noise signal of the first path and the anti-noise signal of the second path, so as to eliminate the noise.

In summary, the spirit of the present invention is to set a plurality of active noise cancellation filter units in the active noise cancellation device of the active noise cancellation earphone, and the output signal of each active noise cancellation filter unit causes other active noise cancellation filter produced by the unit The redundant components are eliminated by decoupling. Therefore, the signals output by the above-mentioned multiple active noise cancellation filter units can be properly stacked in accordance with the real noise situation, and the output noise cancellation signals can be It is more in line with the received noise and can more properly cancel the noise.

Although the elements described above are included in FIGS. 1 to 9 , it is not excluded that more additional elements may be used to achieve better technical effects without violating the spirit of the invention. In addition, although the flow chart of FIG. 10 is executed in a specified order, those skilled in the art can modify the order of these steps without violating the spirit of the invention under the premise of achieving the same effect. Therefore, the present invention does not It is not limited to use only the sequence described above. In addition, those skilled in the art may also integrate several steps into one step, or perform more steps sequentially or in parallel in addition to these steps, and the present invention is not limited thereby.

Although the present invention is described using the above examples, it should be noted that these descriptions are not intended to limit the present invention. On the contrary, the invention covers modifications and similar arrangements obvious to those skilled in the art. Therefore, the claims of the application must be interpreted in the broadest manner to include all obvious modifications and similar arrangements.

20: Active noise reduction integrated circuits that can stack multiple anti-noise signals

21:Audio conversion equipment

201: The first microphone

202:Second microphone

203: The first active noise cancellation filter unit

204: The second active noise cancellation filter unit

205: Physical channel

40: the first decoupling unit

401: The first channel analog filter

402: The first addition circuit

Claims (12)

A stackable multiple active noise reduction integrated circuit, comprising: a first path outputting a first path anti-noise signal, wherein the first path anti-noise signal is converted into a first signal by a physical channel, and the first path The path includes: a first active noise cancellation filter unit for generating a first anti-noise signal; a second path for receiving an error signal containing a component of the first signal, and outputting a second path anti-noise signal to The physical channel, the second path includes: a second active noise cancellation filter unit for generating a second anti-noise signal, wherein the second anti-noise signal derives the second path anti-noise signal; and a first The decoupling unit is used for removing the component of the first signal in the second path based on the first anti-noise signal. The stackable multiple active noise reduction integrated circuit according to claim 1, wherein the first decoupling unit includes: a first channel analog filter, used to simulate the physical channel, and receive the first anti-noise signal , to generate a first decoupling signal; and a first adding circuit, including a first input port, a second input port and an output port, wherein the first input port of the first adding circuit receives the first For decoupling signals, the second input port of the first adding circuit receives the error signal, and the output port of the first adding circuit is coupled to the second active noise cancellation filter unit. The stackable multiple active noise reduction integrated circuit according to claim 1, wherein the first The decoupling unit includes: a first channel analog filter for simulating the physical channel, receiving the first anti-noise signal to generate a first decoupling signal; and a third active noise cancellation filter unit, wherein the The filtering operation of the third active noise cancellation filter unit is the same as that of the second active noise cancellation filter unit, wherein the third active noise cancellation filter unit receives the first decoupling signal and generates a third anti-noise signal; A first addition circuit includes a first input port, a second input port and an output port, wherein the first input port of the first addition circuit receives the third anti-noise signal, and the first addition circuit of the first addition circuit receives the third anti-noise signal. Two input ports receive the second anti-noise signal; and a second adding circuit includes a first input port, a second input port and an output port, wherein the first input port of the second adding circuit is coupled to the The output port of the first addition circuit, the second input port of the second addition circuit receives the first anti-noise signal, wherein, the first anti-noise signal passes through the signal superposition of the first addition circuit and the second addition circuit , the second anti-noise signal and the first decoupling signal are synthesized into a noise cancellation signal. The stackable multiple active noise reduction integrated circuit according to claim 1, wherein the first decoupling unit includes: a third active noise cancellation filter unit, wherein the filtering operation of the third active noise cancellation filter unit The filtering operation is the same as that of the second active noise cancellation filter unit, wherein the third active noise cancellation filter unit receives the first anti-noise signal to generate a third anti-noise signal; a first channel analog filter is used for Simulating the physical channel, receiving the third anti-noise signal to generate a first decoupling signal; a first adding circuit, including a first input port, a second input port and an output port, wherein the first input port of the first adding circuit receives the first decoupling signal, and the second input port of the first adding circuit receives the first anti-noise signal; and a second adding circuit includes a first An input port, a second input port and an output port, wherein the first input port of the second adding circuit is coupled to the output port of the first adding circuit, and the second input port of the second adding circuit receives the first The second anti-noise signal, wherein the signals passed through the first adding circuit and the second adding circuit are superimposed, and the first anti-noise signal, the second anti-noise signal and the first decoupling signal are synthesized into a noise canceling signal. The stackable multiple active noise reduction integrated circuit as described in Claim 1, wherein the physical channel is a first physical channel, wherein the anti-noise signal of the second path is converted into a fourth signal by a second physical channel , wherein the error signal is a first error signal, wherein the first path receives a second error signal containing components of the fourth signal, wherein the stackable multiple active noise reduction IC further comprises: A second decoupling unit is used for removing a component of the fourth signal in the first path based on the second anti-noise signal. The stackable multiple active noise reduction integrated circuit as described in Claim 1, wherein the anti-noise signal of the second path is converted into a second signal by the physical channel, wherein the error signal further includes the second signal component, wherein the first path receives the error signal, wherein the stackable multiple active noise reduction IC further includes: a second decoupling unit for removing the first error signal based on the second anti-noise signal components of the second signal in the path. The stackable multiple active noise reduction integrated circuit as described in claim 6, further comprising: a third path outputting a third path anti-noise signal, wherein the third path anti-noise signal The signal is converted into a third signal by the physical channel, wherein the error signal further contains components of the third signal, and the third path includes: a third active noise cancellation filter unit for generating a third anti-noise signal ; and a third decoupling unit for removing components of the third signal in the second path based on the third anti-noise signal, and further for removing components of the first path based on the third anti-noise signal components of the third signal. The stackable multiple active noise reduction integrated circuit as described in claim 6, wherein the second decoupling unit includes: a second channel analog filter for simulating the physical channel and receiving the second anti-noise signal , to generate a second decoupling signal; and a second adding circuit, including a first input port and a second input port and an output port, wherein the first input port of the second adding circuit receives the second Decoupling the signal, the second input port of the second adding circuit receives the error signal, and the output port of the second adding circuit is coupled to the first active noise elimination filter unit. An active noise reduction earphone, comprising: a stackable multiple active noise reduction integrated circuit as described in any one of claims 1 to 8; and an audio conversion device, comprising: a loudspeaker, used to The path anti-noise signal and the second path anti-noise signal are played to eliminate noise, wherein the loudspeaker is a part of the physical channel; and a microphone is used to receive the noise of the ear canal echo and convert it into the error signal. A stackable multiple active noise reduction method is suitable for a sound playback device with multiple active noise cancellation filter units. The stackable multiple active noise reduction method includes: providing a first path, outputting a first path anti-noise signal, wherein The anti-noise signal of the first path is converted into a first signal by a physical channel, and the first path includes: a first active noise elimination filter unit for generating a first anti-noise signal; providing a second path for receiving An error signal containing a component of the first signal, and outputting a second path anti-noise signal to the physical channel, the second path includes: a second active noise cancellation filter unit for generating a second anti-noise signal , wherein the second anti-noise signal derives the second path anti-noise signal; removes the component of the first signal in the second path based on the first anti-noise signal; and based on the first path anti-noise signal and the The anti-noise signal of the second path is played to eliminate noise. The stackable multiple active noise reduction method according to claim 10, wherein removing the first signal component in the second path based on the first anti-noise signal includes: according to the physical channel, the first anti-noise signal converted into a decoupling signal; and performing decoupling through the decoupling signal at the input end of the second active noise cancellation filter unit, so as to remove the component of the first signal in the second path. According to the stackable multiple active noise reduction method described in claim 10, removing the component of the first signal in the second path based on the first anti-noise signal includes: filtering according to the physical channel and the second active noise reduction The transfer function of the unit generates a decoupling signal; and at the output of the second active noise cancellation filter unit, the decoupling signal is used to decoupling to remove components of the first signal in the second path.

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