1. An active noise reduction method for a semi-in-ear headphone, comprising:

playing an initial noise reduction signal and a test signal through a loudspeaker, wherein the initial noise reduction signal is determined according to a feedforward signal and an initial noise reduction coefficient, the feedforward signal comprises an environment noise signal, and the test signal is uncorrelated with the environment noise signal;

collecting a feedback signal through an error microphone, wherein the feedback signal is a superposition signal of an environmental noise signal, a noise reduction signal and a test signal transmitted to the error microphone;

determining a first echo transfer function according to the feedback signal and the test signal, wherein the first echo transfer function is a transfer function of a path of a playing signal of the loudspeaker reflected to the error microphone through a pinna of a user;

and determining a final noise reduction coefficient according to the first echo transfer function.

2. The active noise reduction method of claim 1, wherein determining a first echo transfer function from the feedback signal and the test signal comprises:

a. determining a first error signal according to the feedback signal, the test signal and a first pre-estimated transfer function;

b. when the expected power of the first error signal does not reach the minimum value, adjusting the first estimated transfer function according to the first error signal and the test signal;

and a, iteratively executing the steps a and b until the expected power of the first error signal reaches a minimum value, and determining the current first estimated transfer function as the first echo transfer function.

3. The active noise reduction method of claim 1, further comprising:

determining a second echo transfer function according to the feedforward signal and the playing signal of the loudspeaker, wherein the second echo transfer function is a transfer function of a path of the playing signal of the loudspeaker reflected to the reference microphone through the auricle of the user;

according to the second echo transfer function and the playing signal of the loudspeaker, eliminating the playing signal transferred to the reference microphone from the feedforward signal to obtain the environmental noise signal in the feedforward signal; and

and determining a final noise reduction signal according to the final noise reduction coefficient and the environment noise signal in the feedforward signal.

4. The active noise reduction method of claim 3, wherein determining a second echo transfer function from the feedforward signal and the playback signal of the loudspeaker comprises:

a. determining a second error signal according to the feedforward signal, the playing signal of the loudspeaker and a second pre-estimated transfer function;

b. when the expected power of the second error signal does not reach the minimum value, adjusting the second pre-estimated transfer function according to the second error signal and the playing signal of the loudspeaker;

and a, iteratively executing the steps a and b until the expected power of the second error signal reaches the minimum value, and determining the current second estimated transfer function as the second echo transfer function.

5. The active noise reduction method according to claim 3 or 4, further comprising:

judging whether the power of the feedback signal keeps convergence;

re-determining the first echo transfer function and the second echo transfer function when it is determined that the power of the feedback signal changes from convergent to divergent.

6. The active noise reduction method according to any of claims 1-4, wherein the test signal comprises: media audio signals, call voice signals.

7. The active noise reduction method of claim 6, further comprising: and determining a tone quality balance coefficient corresponding to the test signal according to the first echo transfer function.

8. An active noise reduction device, comprising:

the active noise reduction module is used for determining an initial noise reduction signal according to an initial noise reduction coefficient and a feedforward signal acquired by a reference microphone and driving a loudspeaker to play the initial noise reduction signal, wherein the feedforward signal comprises an environment noise signal;

a first determining module, configured to determine a first echo transfer function according to a feedback signal acquired by an error microphone and a test signal played by the speaker, where the test signal is uncorrelated with the ambient noise signal, the feedback signal is a superimposed signal of the ambient noise signal, a noise reduction signal and the test signal transmitted to the error microphone, and the first echo transfer function is a transfer function of a path where a playing signal of the speaker is reflected to the error microphone through a pinna of a user;

and the second determining module is used for determining a final noise reduction coefficient according to the first echo transfer function.

9. A semi-in-ear active noise reducing headphone, comprising the active noise reducing apparatus of claim 8.

10. A computer readable storage medium comprising computer instructions stored thereon, which when executed by a processor, cause the processor to perform the active noise reduction method of any of claims 1-7.

Background

Compared with other types of earphones, the half-in-ear earphone has the advantages of being sanitary to use, comfortable to wear, free of foreign body sensation and stethoscope effect, and is very popular with users.

However, the semi-in-ear earphone has poor sealing property with the ear canal, and cannot effectively block noise. Therefore, the user is easily affected by external noise when using the half-in-ear headphone.

Disclosure of Invention

In view of the above, the present application provides an active noise reduction method, an active noise reduction device, a semi-in-ear active noise reduction earphone and a computer readable storage medium, so that the semi-in-ear earphone has excellent noise reduction performance.

In a first aspect, an active noise reduction method is provided. The active noise reduction method comprises the following steps: playing an initial noise reduction signal and a test signal through a loudspeaker, wherein the initial noise reduction signal is determined according to a feedforward signal and an initial noise reduction coefficient, the feedforward signal comprises an environment noise signal, and the test signal is uncorrelated with the environment noise signal; collecting a feedback signal through an error microphone, wherein the feedback signal is a superposition signal of an environmental noise signal, a noise reduction signal and a test signal transmitted to the error microphone; determining a first echo transfer function according to the feedback signal and the test signal, wherein the first echo transfer function is a transfer function of a path of a playing signal of the loudspeaker reflected to the error microphone through a pinna of a user; and determining a final noise reduction coefficient according to the first echo transfer function.

With reference to the first aspect, in some embodiments, determining a first echo transfer function from the feedback signal and the test signal includes: a. determining a first error signal according to the feedback signal, the test signal and a first pre-estimated transfer function; b. when the expected power of the first error signal does not reach the minimum value, adjusting the first estimated transfer function according to the first error signal and the test signal; and a, iteratively executing the steps a and b until the expected power of the first error signal reaches a minimum value, and determining the current first estimated transfer function as the first echo transfer function.

With reference to the first aspect, in some embodiments, the active noise reduction method further includes: determining a second echo transfer function according to the feedforward signal and the playing signal of the loudspeaker, wherein the second echo transfer function is a transfer function of a path of the playing signal of the loudspeaker reflected to the reference microphone through the auricle of the user; according to the second echo transfer function and the playing signal of the loudspeaker, eliminating the playing signal transferred to the reference microphone from the feedforward signal to obtain the environmental noise signal in the feedforward signal; and determining a final noise reduction signal according to the final noise reduction coefficient and the environment noise signal in the feedforward signal.

With reference to the first aspect, in some embodiments, determining a second echo transfer function from the feedforward signal and the playback signal of the loudspeaker includes: a. determining a second error signal according to the feedforward signal, the playing signal of the loudspeaker and a second pre-estimated transfer function; b. when the expected power of the second error signal does not reach the minimum value, adjusting the second pre-estimated transfer function according to the second error signal and the playing signal of the loudspeaker; and a, iteratively executing the steps a and b until the expected power of the second error signal reaches the minimum value, and determining the current second estimated transfer function as the second echo transfer function.

With reference to the first aspect, in some embodiments, the active noise reduction method further includes: judging whether the power of the feedback signal keeps convergence; re-determining the first echo transfer function and the second echo transfer function when it is determined that the power of the feedback signal changes from convergent to divergent.

With reference to the first aspect, in some embodiments, the test signal comprises: media audio signals, call voice signals.

With reference to the first aspect, in some embodiments, the active noise reduction method further includes: and determining a tone quality balance coefficient corresponding to the test signal according to the first echo transfer function.

In a second aspect, an active noise reduction device is provided. This active noise reduction device includes: the active noise reduction module is used for determining an initial noise reduction signal according to an initial noise reduction coefficient and a feedforward signal acquired by a reference microphone and driving a loudspeaker to play the initial noise reduction signal, wherein the feedforward signal comprises an environment noise signal; a first determining module, configured to determine a first echo transfer function according to a feedback signal acquired by an error microphone and a test signal played by the speaker, where the test signal is uncorrelated with the ambient noise signal, the feedback signal is a superimposed signal of the ambient noise signal, a noise reduction signal and the test signal transmitted to the error microphone, and the first echo transfer function is a transfer function of a path where a playing signal of the speaker is reflected to the error microphone through a pinna of a user; and the second determining module is used for determining a final noise reduction coefficient according to the first echo transfer function.

In a third aspect, a semi-in-ear active noise reducing headphone is provided. The semi-in-ear active noise reducing headphone comprises an active noise reducing arrangement as described in the second aspect.

In a fourth aspect, a computer-readable storage medium is provided. The computer readable storage medium comprises computer instructions stored thereon which, when executed by a processor, cause the processor to perform the active noise reduction method according to the first aspect.

The active noise reduction method provided by the embodiment of the application is characterized in that the first echo transfer function is determined, and the noise reduction coefficient of the filter is adjusted according to the first echo transfer function, so that the influence of in-ear echoes on the noise reduction effect is eliminated, the problem of unsatisfactory noise reduction effect caused by poor wearing consistency of the semi-in-ear earphone is solved, and the noise reduction effect of the semi-in-ear earphone is improved.

Drawings

In order to make the objects, technical solutions and advantages of the embodiments of the present application more apparent, the embodiments of the present application will be described in further detail below with reference to the accompanying drawings. It is to be understood that the drawings form a part of the specification, illustrate the present application together with embodiments thereof, and are not to be construed as limiting the present application. Unless otherwise indicated, like reference numbers and designations in the drawings generally refer to like steps or components.

FIG. 1 is a schematic diagram of an exemplary active noise reduction system.

Fig. 2 is a schematic diagram of an active noise reduction system according to an embodiment of the present application.

Fig. 3 is a schematic flow chart of an active noise reduction method according to an embodiment of the present application.

Fig. 4 is a schematic flow chart illustrating a process of determining a first echo transfer function according to an embodiment of the present application.

Fig. 5 is a schematic diagram of an active noise reduction system according to another embodiment of the present application.

Fig. 6 is a schematic flowchart of an active noise reduction method according to another embodiment of the present application.

Fig. 7 is a schematic flowchart illustrating a process of determining a second echo transfer function according to an embodiment of the present application.

Fig. 8 is a schematic structural diagram of an active noise reduction device according to an embodiment of the present application.

Fig. 9 is a schematic structural diagram of an electronic device according to an embodiment of the present application.

Detailed Description

Compare in-ear earphone and package ear formula earphone, half in-ear earphone can't form effectual sealed between earphone main part and user's the ear when using, has the acoustics to reveal. Therefore, the semi-in-ear headphone can hardly implement passive noise reduction.

As a new noise reduction means, the active noise reduction technology has achieved good application results on in-ear earphones and over-the-ear earphones. However, practical studies have found that the existing active noise reduction technology cannot be effectively applied to a semi-in-ear headphone, and the actual noise reduction effect is extremely poor, which has many problems.

For the sake of understanding, the following describes problems of the conventional active noise reduction technology with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of an exemplary active noise reduction system.

As shown in fig. 1, the active noise reduction system includes: reference microphone 110, filter 120, speaker 130, and error microphone 140.

The dotted line is used to indicate a propagation path of an acoustic signal other than the circuit, for example, a primary path formed with reference to a space between the microphone 110 and the error microphone 140, and a secondary path formed by the speaker 130 itself and the space between the speaker 130 and the error microphone 140.

x (z) represents the ambient noise signal at the reference microphone 110. P (z) represents the transfer function of the primary path. G (z) represents a transfer function of the secondary path.

In the existing active noise reduction technology, an off-line design is usually adopted to determine the noise reduction coefficient w (z) of the filter based on the primary path transfer function p (z) and the secondary path transfer function g (z). The theory behind this design is discussed below in conjunction with fig. 1.

To achieve effective noise reduction, the residual noise signal at the error microphone 140 needs to approach zero, and therefore, there needs to be:

e(z)＝x(z)·W(z)·G(z)+x(z)·P(z)→0(1)

this gives:

where z is frequency, e (z) represents the residual noise signal at the error microphone 140, x (z) represents the ambient noise signal acquired by the reference microphone 110, p (z) represents the primary path transfer function, g (z) represents the secondary path transfer function, and w (z) represents the noise reduction coefficients of the filter 120.

Theoretically, the noise reduction coefficient determined based on the method can realize good noise reduction effect.

Specifically, referring again to fig. 1, the ambient noise x (z) is transmitted to the spatial point of the error microphone 140 via the primary path to form the noise signal x (z) · p (z). Meanwhile, the filter 120 is calculated according to the environmental noise x (z) and the filter coefficient w (z) collected by the reference microphone 110To the noise reduction signal x (z) W (z). The noise reduction signal x (z) · W (z) is transmitted to the spatial point of the error microphone 140 via the secondary path, forming the noise reduction signal x (z) · W (z) · G (z). Since the noise reduction coefficient of the filter 120 isTherefore, at the spatial point of the error microphone 140, the noise reduction signals x (z) · w (z) · g (z) can effectively cancel the noise signals x (z) · p (z), thereby achieving a better noise reduction effect.

However, this off-line design method of noise reduction coefficient is designed for an in-ear earphone, and the effective premise is that the noise reduction signal output by the speaker can be fully injected into the ear canal of the user in the form of direct sound, i.e. the earphone and the ear of the user need to form an effective seal.

Due to the poor sealing performance of the half-in-ear earphone, the noise reduction signal output by the speaker cannot completely enter the ear canal of the user in the form of direct sound, and a part of the noise reduction signal leaks through the gap and is reflected by the auricle of the user and then enters the ear canal again. The noise reduction signal entering the ear canal after being reflected by the auricle can not effectively offset the environmental noise signal, and can be picked up by the error microphone, thereby causing interference to the effective operation of the active noise reduction system.

To make matters worse, the acoustic characteristics of the path through which the noise reduction signal is reflected back to the ear canal via the pinna of the user vary from person to person and from time to time due to different ear shapes of different users and different wearing positions of the same user at different times. This further increases the difficulty of applying active noise reduction techniques to semi-in-ear headphones.

In order to solve the problems, the active noise reduction technology is improved.

Embodiments of the present application are described in detail below with reference to the accompanying drawings. It should be understood that the present application may be embodied in various forms and should not be construed as limited to the embodiments set forth herein.

Fig. 2 is a schematic diagram of an active noise reduction system according to an embodiment of the present application.

As shown in fig. 2, the active noise reduction system further includes a first echo path simulation unit 250, a first adder 260, and a first adaptive unit 270, in addition to the reference microphone 210, the filter 220, the speaker 230, and the error microphone 240.

The dotted line is used to indicate a propagation path of an acoustic signal other than the circuit, for example, a primary path formed with reference to a space between the microphone 210 and the error microphone 240, a secondary path formed by the speaker 230 itself and the space between the speaker 230 and the error microphone 240, and a path (hereinafter, referred to as a first echo path) where a playback signal of the speaker 230 is reflected to the error microphone 240 via a pinna of the user.

x (z) represents the ambient noise signal at the reference microphone 210. y (z) represents a test signal that is uncorrelated with the ambient noise signal. P (z) represents the transfer function of the primary path. G (z) represents a transfer function of the secondary path. H₁(z) represents a transfer function of the first echo path (hereinafter referred to as a first echo transfer function).

It should be understood that in the active noise reduction system, the filter 220, the first echo path simulation unit 250, the first adder 260, and the first adaptation unit 270 may be a logic unit, a physical unit, or a combination of both logic and physical units. Here, the physical unit refers to a physical unit constituted by hardware, and the logical unit refers to a virtual unit constituted by a computer-executable program.

Fig. 3 is a schematic flow chart of an active noise reduction method according to an embodiment of the present application.

As shown in fig. 3, the active noise reduction method may include steps S110 to S140. The active noise reduction method may be implemented by, for example, the active noise reduction system shown in fig. 2.

The active noise reduction method is described in detail below with reference to fig. 2 and 3.

In step S110, an initial noise reduction signal and a test signal are played through a speaker.

Illustratively, the speaker 230 may output a playback signal, which may include an initial noise reduction signal and a test signal. The initial noise reduction signal may be determined based on the feedforward signal (i.e., the signal acquired by the reference microphone 210) and the initial noise reduction coefficient of the filter 220 (i.e., the noise reduction coefficient to be adjusted).

Specifically, filter 220 may calculate a corresponding initial noise reduction signal based on the feedforward signal and the initial noise reduction coefficient, and speaker 230 may then play the initial noise reduction signal.

Here, the test signal is an audio signal that is not correlated with the ambient noise signal. In some embodiments, the test signal may be an audio signal that is played specifically for determining the first echo transfer function. In some embodiments, the test signal may also be an audio signal generated by the user, such as a multimedia audio signal like music, video, etc., or a speech signal for conversation, etc.

The audio signal generated by the use of the user is used as the test signal, so that the normal use of the user can be ensured in the adjustment process of the noise reduction coefficient. Therefore, no special test signal is required to be added, so that the adjustment of the noise reduction coefficient can be realized during normal use of a user, such as calling or listening to music.

In step S120, a feedback signal is collected by the error microphone.

The feedback signal refers to a signal collected by the error microphone 240, which is a superimposed signal of the environmental noise signal, the noise reduction signal and the test signal transmitted to the error microphone 240.

In step S130, a first echo transfer function is determined according to the feedback signal and the test signal.

For example, the first echo path simulation unit 250 may simulate the first echo path to obtain an estimated first echo transfer function(hereinafter referred to as the first estimated transfer function). In some embodiments, initially, the first predicted transfer functionMay be determined randomly.

The first adaptive unit 270 may determine the first estimated transfer function according to the test signal y (z) and the feedback signalWhether the optimum is reached. If the first estimated transfer functionIf not, adjusting the first estimated transfer function to obtain a new first estimated transfer functionAnd determining a new first estimated transfer function again according to the test signal y (z) and the feedback signalWhether the optimum is reached. Repeating the above steps until the first estimated transfer functionReach the optimum and the first pre-estimated transfer function when reaching the optimumA first echo transfer function is determined.

In this way, the first estimated transfer function can be realizedSo as to continuously approximate the real first echo transfer function H which varies from person to person and from time to time₁(z)。

As an implementation manner, the first pre-estimated transfer function can be obtained according to the test signal y (z), the feedback signal and the first pre-estimated transfer functionTo determine a first error signal e₁(z) and on the basis of the first error signal e₁(z) to determine whether a termination iteration condition is satisfied.

This implementation is described in detail below with reference to the figures.

Fig. 4 is a schematic flow chart illustrating a process of determining a first echo transfer function according to an embodiment of the present application.

In step S131, a first error signal is determined according to the feedback signal, the test signal and the first estimated transfer function.

Illustratively, when the first pre-estimated transfer functionIf the optimization is not reached, the first adaptive unit 270 may apply the first predicted transfer functionAnd (6) adjusting. The first echo path simulation unit 250 may estimate the transfer function according to the adjusted first estimated transfer functionThe noise reduction coefficients of the filter 220 are adjusted. The filter 220 may use the adjusted noise reduction coefficients to determine an adjusted noise reduction signal. The speaker 230 may play the adjusted noise reduction signal such that the error microphone 240 collects an adjusted feedback signal corresponding to the adjusted noise reduction signal.

The first echo path simulation unit 250 may be based on a first pre-estimated transfer functionSimulating the influence of the first echo path, and processing the test signal y (z) to obtain a first estimated signalThe summer 260 may sum the feedback signal and the processed test signalComparing to obtain the error between them, i.e. the first error signal e₁(z)。

In step S132, the current first error signal e is determined₁(z) whether the desired power of (z) reaches a minimum value.

Exemplarily, the first adaptation unit 270 may determine a current first error signal e₁(z) desired energy (i.e. first error signal e)₁Energy of (z) has reached a minimum.

If the current first error signal e₁(z) if the desired power does not reach the minimum value, performing step S133; if the current first error signal e₁(z) the desired power reaches the minimum value, step S134 is performed.

In step S133, the first estimated transfer function is adjusted, and step S131 is executed again based on the adjusted first estimated transfer function.

Illustratively, if the first adaptation unit 270 determines the current first error signal e₁(z) the desired power does not reach a minimum value, again based on the test signal y (z) and the first error signal e₁(z) to the first estimated transfer functionMakes an adjustment and determines again the first error signal e₁The desired power of (z) reaches a minimum. This process is repeated until the first error signal e₁The desired power of (z) reaches a minimum.

In step S134, the current first estimated transfer function is determined as the first echo transfer function.

Illustratively, if the first adaptation unit 270 determines the current first error signal e₁(z) the desired power has reached a minimum value, terminating the iteration and applying the first error signal e₁(z) first estimated transfer function at which desired power reaches a minimumA first echo transfer function is determined.

Whether the first predicted transfer function is optimal or not is determined by judging whether the expected power of the first error signal reaches the minimum value or not, and the first predicted transfer function when the expected power of the first error signal reaches the minimum value is determined as the first echo transfer function, so that the determined first echo transfer function is closer to the real first echo transfer function.

In step S140, a final noise reduction coefficient is determined according to the first echo transfer function.

As an implementation manner, the filter 220 may include a base filter 221 and a correction filter 222, the noise reduction coefficient of the base filter 221 may be set in an off-line manner, and the coefficient of the correction filter 222 may be adjusted according to the determined first echo transfer function.

More specifically, in some embodiments, the noise reduction coefficients W (z) of the base filter 221 may be configured toThe noise reduction coefficient of the correction filter 222 may be configured toNoise reduction coefficient of filter 220

At the beginning, the first estimated transfer functionMay be 0, so that initially the overall noise reduction coefficient of filter 220 is its base noise reduction coefficient (w (z) scaled off-line). In an iterative process, transfer function is estimated along with the first estimationFirst echo function H which is continuously close to reality₁(z), the noise reduction coefficients of the filter 220 are continuously adjusted. When the first estimated transfer functionWhen the optimum is reached, overlapStopping at the first estimated transfer functionIs determined as the first echo transfer function, and accordingly, the noise reduction coefficient at this time of the filter 220 is determined as the final noise reduction coefficient.

It should be understood that although in this embodiment, the first pre-estimated transfer function is performed each timeAfter the update, the noise reduction coefficient of the filter 220 is updated, so that the noise reduction coefficient of the filter 220 and the first estimated transfer function are updatedAnd synchronously iterating to the optimal value. However, in other embodiments of the present application, the first estimated transfer function isIn the iterative process, the noise reduction coefficient of the filter 220 may also be constant (i.e., active noise reduction is performed by using the noise reduction coefficient calibrated off-line), and may be based on the first estimated transfer functionWhen the optimal state is reached, the transfer function is estimated according to the optimal first estimationTo adjust the noise reduction coefficients of the filter 220.

The active noise reduction method provided by the embodiment of the application eliminates the influence of in-ear echoes on the noise reduction effect by determining the first echo transfer function and adjusting the noise reduction coefficient of the filter according to the first echo transfer function, solves the problem of unsatisfactory noise reduction effect caused by poor wearing consistency of the semi-in-ear earphone, and improves the noise reduction effect of the semi-in-ear earphone.

In addition, in the active noise reduction mode provided by the embodiment of the application, the noise reduction mode does not need to be started after the final noise reduction coefficient is determined. Before the final noise reduction coefficient is determined, noise reduction can be performed based on the adjusted noise reduction coefficient, so that the response of a noise reduction system is more timely, and a user can enjoy noise reduction experience after the earphone is started.

In some embodiments, the above-mentioned process of determining the first echo transfer function by iteratively adjusting may be implemented by using an adaptive algorithm. For example, an LMS (Least Mean Square) algorithm or an NLMS (Normalized Least Mean Square) algorithm may be employed.

The semi-in-ear earphone has poor sealing performance, and can not only lead a noise reduction signal to reach an error microphone after being reflected by the auricle of a user, but also lead a playing signal of a loudspeaker to reach a reference microphone after being reflected by the auricle of the user. In this case, the signal picked up by the reference microphone will no longer contain only the ambient noise signal, which also affects the noise reduction effect of the active noise reduction system.

Fig. 5 is a schematic diagram of an active noise reduction system according to another embodiment of the present application.

As shown in fig. 5, the active noise reduction system is substantially the same as the active noise reduction system of fig. 2. The difference is mainly that compared to the active noise reduction system in fig. 2, the active noise reduction system further comprises: a second echo path simulation unit 280, a second adder 290 and a second adaptation unit 2100.

In fig. 5, the dashed line connecting the reference microphone 210 and the output side of the speaker 230 is used to indicate a path of the playback signal of the speaker 230 to the reference microphone 210 after being reflected by the pinna of the user, and is referred to as a second echo path hereinafter. H₂(z) is used to represent the transfer function of the second echo path.

It should be understood that in this embodiment, the second echo path modeling unit 280, the adder 290, and the adaptation unit 2100 may be logical units, physical units, or a combination of both logical and physical units. Here, the physical unit refers to a physical unit constituted by hardware, and the logical unit refers to a virtual unit constituted by a computer-executable program.

Fig. 6 is a schematic flowchart of an active noise reduction method according to another embodiment of the present application. The active noise reduction method provided by this embodiment can be implemented by the active noise reduction system shown in fig. 5, for example.

The active noise reduction method is described in detail below with reference to fig. 5 and 6.

As shown in fig. 6, the active noise reduction method is substantially the same as the active noise reduction method in fig. 3, but the difference is that the active noise reduction method further includes steps S150 to S170, compared to the active noise reduction method in fig. 3. For the sake of brevity, the same parts will not be described again, and only different parts will be described here.

In step S150, a second echo transfer function is determined based on the feedforward signal and the playback signal of the loudspeaker.

For example, the second echo path simulation unit 280 may simulate the second echo path to obtain the estimated second echo transfer function(hereinafter referred to as the second estimated transfer function). In some embodiments, initially, the second predicted transfer functionMay be determined randomly.

The second adaptive unit 2100 may determine the second predicted transfer function based on the feedforward signal and the playback signal of the speakerWhether the optimum is reached. If the second estimated transfer functionIf not, adjusting the second estimated transfer function to obtain the adjusted second estimated transfer functionAnd judging the adjusted second pre-estimated transfer function again according to the feedforward signal and the playing signal of the loudspeakerWhether the optimum is reached. Repeating the above steps until the second estimated transfer functionReach the optimum and the second pre-estimated transfer function when reaching the optimumA second echo transfer function is determined.

In this way, the second estimated transfer function can be realizedIs iterated to continuously approximate the true second echo transfer function H₂(z)。

As an implementation, the transfer function can be estimated according to the feedforward signal, the playing signal of the loudspeaker and the second estimated transfer functionDetermining a second error signal test signal e₂(z) and on the basis of the second error signal e₂(z) to determine whether a termination iteration condition is satisfied.

This implementation is described in detail below with reference to the figures.

Fig. 7 is a schematic flowchart illustrating a process of determining a second echo transfer function according to an embodiment of the present application.

In step S151, a second error signal is determined based on the feedforward signal, the playback signal of the speaker, and the second estimated transfer function.

Illustratively, the second echo path simulation unit 280 may be based on a second estimated transfer functionThe influence of the second echo path is simulated and the playback signal of the loudspeaker 230 is processed to obtain a second estimated signal.Here, the second estimated signal is a signal of the analog playback signal transmitted to the reference microphone 210 via the second echo path. The second adder 290 can compare the feedforward signal with the second estimation signal to obtain an error therebetween, i.e. a second error signal e₂(z). The filter 220 may apply the second error signal e₂(z) as input, a second error signal e based on a noise reduction coefficient₂(z) processing to obtain a noise reduction signal. The speaker 230 may play the noise reduction signal and the test signal y (z) to obtain a playing signal of the speaker 230.

In step S152, the current second error signal e is determined₂(z) whether the desired power of (z) reaches a minimum value.

Exemplarily, the second adaptation unit 2100 may determine a current second error signal e₂Desired power of (z) (i.e. second error signal e)₂Energy of (z) has reached a minimum.

If the current second error signal e₂(z) if the desired power does not reach the minimum value, performing step S153; if the current second error signal e₂(z) the desired power reaches the minimum value, step S154 is performed.

In step S153, the second estimated transfer function is adjusted, and step S151 is executed again based on the adjusted second estimated transfer function.

Illustratively, if the second adaptation unit 2100 determines the current second error signal e₂(z) the desired power does not reach a minimum value, based on the playback signal of the loudspeaker and the second error signal e₂(z) adjusting the second echo path simulation unit 280 to obtain an updated second estimated transfer function

The second adaptation unit 2100 may again determine the second error signal e based on the updated correlation signal₂The desired power of (z) reaches a minimum. This process is repeated until the second error signal e₂The desired power of (z) reaches a minimum.

In step S154, the current second predicted transfer function is determined as the second echo transfer function.

Illustratively, if the second adaptation unit 2100 determines the current second error signal e₂(z) the desired power has reached a minimum value, terminating the iteration and applying the current second estimated transfer functionA second echo transfer function is determined.

Whether the second estimated transfer function is optimal or not is determined by judging whether the expected power of the second error signal reaches the minimum value or not, and the second estimated transfer function when the expected power of the second error signal reaches the minimum value is determined as the second echo transfer function, so that the determined second echo transfer function is closer to the real second echo transfer function which is different from person to person and time to time.

In step S160, the playback signal transmitted to the reference microphone is cancelled from the feedforward signal according to the second echo transfer function and the playback signal of the loudspeaker, so as to obtain an ambient noise signal in the feedforward signal.

For example, after determining the second echo transfer function, the second echo path simulation unit 280 may simulate a real second echo path according to the obtained second echo transfer function, and process the playing signal of the speaker 230 to obtain the playing signal transmitted to the reference microphone 210 via the second echo path.

The second adder 290 may compare the feedforward signal collected by the reference microphone 210 with the playing signal transmitted to the reference microphone 210 through the second echo path, so as to eliminate the playing signal transmitted to the reference microphone 210 through the second echo path from the feedforward signal, and recover the ambient noise signal in the feedforward signal.

In response to the second error signal e₂(z) in embodiments where the second echo transfer function is determined, the transfer function is estimated as a function of the second estimateContinuously approximating the true second echo transfer function H₂(z) the second estimated signal continuously approximates the true playback signal transmitted to the reference microphone 210 via the second echo path, and accordingly the second error signal e₂(z) also closely approximates the ambient noise signal.

When the second error signal e₂After the desired power of (z) reaches the minimum value, the second estimated signal is infinitely close to the playing signal of the feedforward signal transmitted to the reference microphone 210 through the second echo path, so that the feedforward signal cancels the second error signal e obtained by the second estimated signal₂(z) an infinitely close to the true ambient noise signal x (z). Second error signal e at this time₂(z) can be used as the ambient noise signal in the feed forward signal.

In step S170, a final noise reduction signal is determined according to the final noise reduction coefficient and the ambient noise signal in the feedforward signal.

Illustratively, after obtaining the final noise reduction coefficient of the filter and the ambient noise signal in the feedforward signal, the filter 220 may use the ambient noise signal in the feedforward signal as an input to determine the final noise reduction signal using the final noise reduction coefficient. The speaker 230 may output the final noise reduction signal to achieve active noise reduction.

By determining the second echo transfer function and eliminating the playing signal transferred to the reference microphone from the feedforward signal according to the second echo transfer function, the ambient noise signal in the feedforward signal can be obtained, so that the influence of the playing signal transferred to the reference microphone on the active noise reduction system can be avoided, and the noise reduction effect is further improved.

The final noise reduction signal is determined according to the final noise reduction coefficient and the environmental noise restored from the feedforward signal, so that the adverse effect caused by poor sealing performance of the semi-in-ear earphone can be effectively offset, and the noise reduction effect of the semi-in-ear earphone is greatly improved.

In some embodiments, the above-mentioned process of determining the second echo transfer function by iteratively adjusting may be implemented by using an adaptive algorithm. For example, an LMS (Least Mean Square) algorithm or an NLMS (Normalized Least Mean Square) algorithm may be employed.

It should be understood that the execution sequence of steps S120 to S140 and steps S150 to S160 is not specifically limited in the embodiments of the present application. That is to say, the embodiment of the present application is not particularly limited to determine the sequence of the first echo transfer function and the second echo transfer function.

In some embodiments, the second echo transfer function may be determined after the first echo transfer function is determined, i.e. after the final noise reduction coefficients are determined.

In some embodiments, the second echo transfer function may be determined first, and then the first echo transfer function may be determined to determine the final noise reduction coefficient.

In some embodiments, determining the first echo transfer function and the second echo transfer function may be performed simultaneously. For example, an iterative update of the second predicted transfer function may be performed during the iterative update of the first predicted transfer function.

In this case, the noise reduction signal changes every time the first estimated transfer function is updated, and the noise reduction signal changes again to cause the playing signal of the speaker to change, thereby affecting the iterative update process of the second estimated transfer function; meanwhile, the noise reduction signal is changed due to each updating of the second estimated transfer function, and the feedback signal acquired by the error microphone is changed due to the change of the noise reduction signal, so that the iterative updating process of the first estimated transfer function is influenced.

That is, in the process of performing iterative updating on the first predicted transfer function and the second predicted transfer function simultaneously, the first predicted transfer function updated each time is applied to the adaptive link of the second predicted transfer function, and similarly, the second predicted transfer function updated each time is applied to the adaptive link of the first predicted transfer function. Therefore, iterative updating of the first estimated transfer function and the second estimated transfer function can be synchronously performed, and the tuning process of the active noise reduction system can be rapidly completed.

When the wearing position of the earphone moves or when the earphone is worn by another user, the transfer functions of the first echo path and the second echo path change, so that the previously determined transfer functions of the first echo path and the second echo path are not applicable any more, and the noise reduction effect is difficult to maintain.

To solve this problem, in some embodiments, the active noise reduction method in the foregoing embodiments may further include the following steps: judging whether the power of the feedback signal keeps convergence; when it is determined that the power of the feedback signal changes from convergent to divergent, the first echo transfer function and the second echo transfer function are re-determined.

Specifically, after the first echo transfer function and the second echo transfer function are determined, the power of the feedback signal collected by the error microphone may be monitored in real time to monitor whether the power of the feedback signal keeps converging. When the power of the feedback signal is detected to be divergent from convergence or not to be converged to the minimum value, the steps in the above embodiment are performed again to re-determine the first echo transfer function and the second echo transfer function, and the active noise reduction system is tuned again.

By judging whether the power of the feedback signal is kept converged or not, whether the wearing condition of the earphone is changed or not can be accurately judged. In this way, the problem of noise reduction effect deterioration caused by the change of the wearing position of the earphone can be effectively solved, and the stability of the noise reduction effect is obviously improved.

It is contemplated that not only the noise reduction signal may be transmitted into the user's ear canal through the first echo path, but also other audio signals, such as multimedia audio signals or speech signals, may be transmitted into the user's ear canal through the first echo path, thereby generating an echo signal. Such echo signals can affect the user experience and, at the same time, affect the operation of the active noise reduction system.

To solve this problem, in some embodiments, the active noise reduction method in the above embodiments may further include the following steps: and determining a tone quality balance coefficient corresponding to the test signal according to the first echo transfer function.

For example, an adaptive equalizer may be branch-compensated for the audio signal (or test signal) and the psychoacoustic equalization coefficients of the adaptive equalizer may be adjusted based on the determined first echo function.

As an implementation manner of the present invention,thus, after the first echo path is determined, the sound quality equalization coefficient eq (z) is determined.

In some embodiments, the adaptive equalizer may be located locally to the headset.

In some embodiments, the adaptive equalizer may also be located on the paired device side of the headset, such as in a music player of a cell phone. In this case, the earphone may send the determined tone quality equalization coefficient to the mobile phone, for example, through bluetooth, and the music player at the mobile phone end may perform spectrum equalization on the audio signal to be played based on the tone quality equalization coefficient, and send the processed audio signal to the earphone for playing.

In this way, echo signals can be effectively cancelled, thereby improving the user experience.

The method embodiment of the active noise reduction method of the present application is described in detail above with reference to fig. 2 to 7, and the device embodiment of the active noise reduction method of the present application is described in detail below with reference to fig. 8. The descriptions of the method embodiments and the apparatus embodiments correspond to each other, and overlapping descriptions are appropriately omitted for the sake of brevity.

Fig. 8 is a schematic structural diagram of an active noise reduction device according to an embodiment of the present application.

As shown in fig. 8, the active noise reduction device includes: an active noise reduction module 310, a first determination module 320, and a second determination module 330.

The active noise reduction module 310 is configured to determine an initial noise reduction signal according to the initial noise reduction coefficient and a feedforward signal collected by the reference microphone, and drive the speaker to play the initial noise reduction signal.

Here, the feedforward signal includes an ambient noise signal.

The first determining module 320 is configured to determine a first echo transfer function according to a feedback signal collected by the error microphone and a test signal played by the speaker.

Here, the test signal is uncorrelated with the ambient noise signal. The feedback signal is a superimposed signal of the ambient noise signal, the noise reduction signal and the test signal delivered to the error microphone. The first echo transfer function is a transfer function of a path of a playing signal of the loudspeaker reflected to the error microphone through a pinna of a user.

The second determining module 330 is configured to determine a final noise reduction coefficient according to the first echo transfer function.

The active noise reduction device provided by the embodiment of the application eliminates the influence of in-ear echoes on the noise reduction effect by determining the first echo transfer function and adjusting the noise reduction coefficient of the filter according to the first echo transfer function, solves the problem of unsatisfactory noise reduction effect caused by poor wearing consistency of the semi-in-ear earphone, and improves the noise reduction effect of the semi-in-ear earphone.

In some embodiments, the first determination module 320 is configured to perform the following steps:

a. determining a first error signal according to the feedback signal, the test signal and the first pre-estimated transfer function;

b. when the expected power of the first error signal does not reach the minimum value, adjusting the first pre-estimated transfer function according to the first error signal and the test signal;

and a, iteratively executing the steps a and b until the expected power of the first error signal reaches a minimum value, and determining the current first estimated transfer function as a first echo transfer function.

In some embodiments, the active noise reduction device further comprises: a third determining module and a fourth determining module.

The third determining module is used for determining a second echo transfer function according to the feedforward signal and the playing signal of the loudspeaker.

Here, the second echo transfer function is a transfer function of a path of a playback signal of the speaker reflected to the reference microphone via the pinna of the user.

And the fourth determining module is used for eliminating the playing signal transmitted to the reference microphone from the feedforward signal according to the second echo transfer function and the playing signal of the loudspeaker so as to obtain an environmental noise signal in the feedforward signal.

The active noise reduction module 310 may also be configured to determine a final noise reduction signal based on the final noise reduction coefficient and the ambient noise signal in the feedforward signal.

In some embodiments, the third determination module is configured to perform the steps of:

a. determining a second error signal according to the feedforward signal, the playing signal of the loudspeaker and the second pre-estimated transfer function;

b. when the expected power of the second error signal does not reach the minimum value, adjusting the second pre-estimated transfer function according to the second error signal and the playing signal of the loudspeaker;

and a step a and a step b are executed iteratively until the current second estimated transfer function is determined to be the second echo transfer function when the expected power of the second error signal reaches the minimum value.

In some embodiments, the active noise reduction apparatus may further include a determination module. The judging module is used for judging whether the power of the feedback signal keeps convergence.

The first determining module 320 is further configured to re-determine the first echo transfer function when the determining module determines that the power of the feedback signal changes from converging to diverging.

The third determining module is further configured to re-determine the second echo transfer function when the determining module determines that the power of the feedback signal changes from convergent to divergent.

In some embodiments, the test signal comprises: media audio signals, call voice signals.

In some embodiments, the active noise reduction apparatus may further include a fifth determining module. And the fifth determining module is used for determining the tone quality equalization coefficient corresponding to the test signal according to the first echo transfer function.

Fig. 9 is a schematic structural diagram of an electronic device according to an embodiment of the present application.

As shown in fig. 9, the electronic apparatus includes: a processor 420 coupled to the memory 410. The processor 420 is configured to perform the active noise reduction method of the previous embodiments based on instructions stored in the memory 410.

The embodiment of the application also provides a semi-in-ear active noise reduction earphone. The semi-in-ear active noise reduction earphone comprises the active noise reduction device.

Embodiments of the present application also provide a computer-readable storage medium having stored thereon computer instructions. The computer program, when executed by a processor, implements the active noise reduction method described above.

In other embodiments of the present application, a computer program product is also provided. The computer product comprises means for performing the active noise reduction method of the preceding embodiments.

It is to be understood that, as used herein, the terms "includes," including, "and variations thereof are intended to be open-ended, i.e.," including, but not limited to. The term "according to" is "at least partially according to". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment".

It should be understood that although the terms "first" or "second", etc. may be used herein to describe various elements (e.g., the first echo path simulating unit, the second echo path simulating unit), these elements are not limited by these terms, which are used only to distinguish one element from another.

In the above embodiments, all or part of the implementation may be realized by software, hardware, firmware or any other combination. When implemented in software, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loaded and executed on a computer, cause the processes or functions described in accordance with the embodiments of the invention to occur, in whole or in part. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable device. The computer instructions may be stored on a computer readable storage medium or transmitted from one computer readable storage medium to another, for example, from one website, computer, server, or data center to another website, computer, server, or data center via wire (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device, such as a server-side, data center, etc., that includes one or more of the available media. The usable medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a magnetic tape), an optical medium (e.g., a Digital Video Disk (DVD)), or a semiconductor medium (e.g., a Solid State Disk (SSD)), among others.

Those of ordinary skill in the art will appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit.

The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.