Headphone active noise reduction method, device and active noise reduction headphone

Abstract

The present application discloses an active noise reduction method and device for headphones, and active noise reduction headphones. The headphones include a speaker and a microphone for collecting sound signals in the ear canal, and the method includes: obtaining a source audio signal input to the speaker and a feedback audio signal collected by the microphone; determining a transfer function based on the source audio signal and the feedback audio signal; determining the fit state between the headphones and the ear canal of a human ear based on the transfer function; and adaptively selecting a corresponding active noise reduction filter based on the fit state between the headphones and the ear canal of a human ear, so as to perform active noise reduction through the active noise reduction filter. The active noise reduction method for headphones of the present application achieves the purpose of adaptively matching the corresponding active noise reduction filter based on the fit state, so that users can feel a good noise reduction effect in different headphone wearing conditions, thereby improving the user experience.

Description

Technical Field

[0001] The present application relates to the field of earphone technology, and in particular to an earphone active noise reduction method, device and an active noise reduction earphone. Background Art

[0002] Headphones are widely used in daily life due to their small size and portability. In addition to using headphones to listen to music and watch videos, headphones also play a role in isolating noise and providing users with a quiet environment. Traditional headphones have limitations in physically isolating mid- and low-frequency noise, so active noise cancellation (ANC) technology has been more widely used in headphones.

[0003] The principle of active noise reduction is to generate a signal with a similar amplitude and opposite phase to the external interference noise to offset the impact of the external interference noise.

[0004] Existing active noise reduction headphones generally achieve noise reduction through active noise reduction filters pre-set in the headphones. However, this method ignores the differences in wearing fit between individual users, resulting in different noise reduction effects felt by different users in the same noise environment, and cannot meet the noise reduction needs of different users. Summary of the invention

[0005] In view of this, the main purpose of the present application is to provide a method and device for active noise reduction of headphones, and active noise reduction headphones, so as to solve the technical problem that existing active noise reduction headphones cannot meet the noise reduction needs of different users.

[0006] According to a first aspect of the present application, a method for active noise reduction of headphones is provided, wherein the headphones include a speaker and a microphone for collecting sound signals in an ear canal, and the method includes:

[0007] Acquire a source audio signal input to the speaker and a feedback audio signal collected by the microphone;

[0008] determining a transfer function based on the source audio signal and the feedback audio signal;

[0009] Determining the fit state between the earphone and the ear canal of a human ear according to the transfer function;

[0010] According to the fitting state of the earphone and the ear canal of the human ear, a corresponding active noise reduction filter is adaptively selected to perform active noise reduction through the active noise reduction filter.

[0011] According to a second aspect of the present application, there is provided an active noise reduction device for headphones, the headphones comprising a speaker and a microphone for collecting an audio signal played by the speaker, the device comprising:

[0012] An audio signal acquisition unit, used to acquire a source audio signal input to the speaker and a feedback audio signal collected by the microphone;

[0013] a transfer function determining unit, configured to determine a transfer function according to the source audio signal and the feedback audio signal;

[0014] a fitting state determining unit, configured to determine a fitting state between the earphone and the ear canal of a human ear according to the transfer function;

[0015] The active noise reduction unit is used to adaptively select a corresponding active noise reduction filter according to the fitting state of the earphone and the human ear canal, so as to perform active noise reduction through the active noise reduction filter.

[0016] According to a third aspect of the present application, an active noise reduction headset is provided, comprising: a speaker, a microphone for collecting sound signals in an ear canal, a processor, and a memory for storing computer executable instructions.

[0017] When the computer executable instructions are executed by the processor, any of the aforementioned headphone active noise reduction methods is implemented.

[0018] According to a fourth aspect of the present application, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores one or more programs, and when the one or more programs are executed by a processor, any of the aforementioned headphone active noise reduction methods is implemented.

[0019] The beneficial effect of the present application is that the headphone active noise reduction method of the embodiment of the present application performs a fit state detection based on the speaker in the headphone and the microphone for collecting sound signals in the ear canal, and then adaptively selects a suitable active noise reduction filter for active noise reduction based on the fit state detection result. The headphone active noise reduction method of the embodiment of the present application achieves good noise reduction effect for different wearing conditions of different users in the same noise environment, meeting the noise reduction needs of different users. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Also, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0021] Figure 1 A schematic diagram of a flow chart of an active noise reduction method for headphones according to an embodiment of the present application;

[0022] Figure 2A schematic diagram of a frequency response curve of a frequency domain transfer function under different lamination states of an embodiment of the present application;

[0023] Figure 3 A schematic diagram of a selection process of an active noise reduction filter according to an embodiment of the present application;

[0024] Figure 4 This is a flowchart of the active noise reduction process of headphones according to an embodiment of the present application;

[0025] Figure 5 This is a schematic diagram of the structure of an active noise reduction device for headphones according to an embodiment of the present application;

[0026] Figure 6 This is a schematic diagram of the structure of an active noise reduction headset in one embodiment of the present application. DETAILED DESCRIPTION

[0027] The exemplary embodiments of the present application will be described in more detail below with reference to the accompanying drawings. These embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art. Although exemplary embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein.

[0028] Normally, active noise reduction headphones need to work when the ear canal is well sealed. Due to the great differences in the structure of the human ear, different users wear them in different ways, and for the sake of wearing comfort, some users may choose earmuffs of different sizes, which will result in different degrees of fit between the headphones and the ear canal. Due to different degrees of fit, the amount of noise that enters the ear through the gap between the headphones and the ear canal is different. If the same noise reduction filter is used, due to different noise amplitudes, the noise cancellation may be less in some wearing situations, so that the same noise reduction filter is used in the same environment, and the noise reduction effect produced is different.

[0029] Based on this, Figure 1 A schematic diagram of a method for active noise reduction of headphones according to an embodiment of the present application is shown. Figure 1 The headset of the embodiment of the present application includes a speaker and a microphone for collecting sound signals in the ear canal. The headset active noise reduction method of the embodiment of the present application includes the following steps S110 to S140:

[0030] Step S110, obtaining a source audio signal input to a speaker and a feedback audio signal collected by a microphone.

[0031] Step S120: determining a transfer function according to the source audio signal and the feedback audio signal.

[0032] Step S130: determining the fit state between the earphone and the ear canal of the human ear according to the transfer function.

[0033] Step S140: adaptively select a corresponding active noise reduction filter according to the fit state between the earphone and the ear canal of the human ear, so as to perform active noise reduction through the active noise reduction filter.

[0034] The active noise reduction method for headphones in the embodiment of the present application detects the fit state of the speaker in the headphones and the microphone for collecting sound signals in the ear canal, and then adaptively selects a suitable active noise reduction filter for active noise reduction based on the fit state detection result. The active noise reduction method for headphones in the embodiment of the present application achieves good noise reduction effects for different wearing conditions of different users in the same noise environment, meeting the noise reduction needs of different users.

[0035] Combine the following Figure 1-4 The above steps S110 - S140 are described in detail.

[0036] Those skilled in the art can easily understand that according to different embodiments of the present invention, the transfer function can be a frequency domain transfer function or a time domain transfer function. The following first describes a specific example of a frequency domain transfer function.

[0037] First, step S110 is executed, that is, obtaining the source audio signal input to the speaker and the feedback audio signal collected by the microphone.

[0038] The embodiment of the present application obtains two signals in total, one signal is a source audio signal sequence input to the speaker, denoted by x=[x(0), x(1), ..., x(N-1)], and the other is a feedback audio signal sequence collected by the microphone, denoted by y=x1+v=[x1(0), x1(1), ..., x1(N-1)]+[v(0), v(1), ..., v(N-1)], where x1 represents the signal played by the speaker collected by the microphone, and v represents the external interference noise collected by the microphone. Then, the two signal sequences are high-pass filtered to filter out the influence of the DC signal.

[0039] In order to reduce the error of frequency component estimation, the above two signals can be further subjected to windowing and frequency domain transformation. Specifically, analysis windows are added to the two signals, such as Hamming windows (w = [w(0), w(1), ..., w(N-1)]), and Fourier transforms are performed to obtain frequency domain signals, which are respectively denoted as X(k) and Y(k), as shown in the following equations (1) and (2):

[0040]

[0041]

[0042] Among them, N represents the number of Fourier transform points, n represents the signal sequence sample points, and k represents the frequency bin (frequency point) ordinal number.

[0043] After the source audio signal input to the speaker and the feedback audio signal collected by the microphone are acquired, step S120 is performed, that is, determining a frequency domain transfer function according to the source audio signal and the feedback audio signal.

[0044] Specifically, in one embodiment of the present application, determining the frequency domain transfer function based on the source audio signal and the feedback audio signal includes: using a preset power spectrum estimation method to calculate the autopower spectrum of the source audio signal, and the cross-power spectrum between the feedback audio signal and the source audio signal; smoothing the autopower spectrum and the cross-power spectrum within a preset time period, respectively, to obtain an average autopower spectrum and an average cross-power spectrum; and determining the frequency domain transfer function based on the ratio of the average cross-power spectrum to the average autopower spectrum.

[0045] First, the autopower spectrum of the source audio signal and the cross-power spectrum between the feedback audio signal and the source audio signal are calculated. The periodogram method can be used to estimate the power spectrum. Of course, those skilled in the art can also choose other types of spectrum estimation methods according to actual needs, which are not specifically limited here.

[0046] Taking the periodogram method as an example, the calculation formula of the autopower spectrum Pxx(k) of the source audio signal is shown in the following formula (3):

[0047]

[0048] The calculation formula of the cross power spectrum Pyx(k) of the feedback audio signal and the source audio signal is shown in the following formula (4):

[0049]

[0050] Among them, * represents conjugation, and E represents mathematical expectation. Since the external interference noise v is irrelevant to the source audio signal x input to the speaker, we have E[V(k)X * (k)]≈0.

[0051] In order to effectively eliminate the influence of non-correlated components in the two signals, the embodiment of the present application performs a smoothing process on the power spectrum. Specifically, the power spectrum within a period of time is mean-smoothed, for example, the time length LenT = 30 frames, then the average auto-power spectrum PxxAve(k) and the average cross-power spectrum PyxAve(k) are calculated as shown in the following formulas (5) and (6):

[0052]

[0053]

[0054] After obtaining the average autopower spectrum PxxAve(k) and the average cross-power spectrum PyxAve(k), the frequency domain transfer function H'(k) can be obtained according to the ratio of the average cross-power spectrum PyxAve(k) to the average autopower spectrum PxxAve(k). The specific calculation method is shown in the following formula (7):

[0055]

[0056] After the frequency domain transfer function is determined according to the source audio signal and the feedback audio signal, step S130 is performed, that is, the fitting state of the earphone and the ear canal of the human ear is detected according to the amplitude of the frequency domain transfer function.

[0057] Specifically, in one embodiment of the present application, detecting the fit state of the earphone and the human ear canal based on the amplitude of the frequency domain transfer function includes: determining the average value of the low-frequency amplitude and the average value of the intermediate-frequency amplitude in the frequency domain transfer function; and detecting the fit state of the earphone and the human ear canal based on the ratio of the average value of the low-frequency amplitude to the average value of the intermediate-frequency amplitude.

[0058] like Figure 2 As shown, a schematic diagram of the frequency response curve of the frequency domain transfer function under different fitting states of an embodiment of the present application is provided. When the degree of fit between the earphone and the human ear canal is different, the low-frequency (100Hz-700Hz) amplitude leakage of the speaker is different. Due to the leakage of the low-frequency amplitude, in the low-frequency band, the worse the fit, the lower the low-frequency amplitude; conversely, the better the fit, the higher the low-frequency amplitude. This is reflected in the frequency response curve of the frequency domain transfer function, that is, the worse the fit, the more the low-frequency amplitude of the frequency response curve decreases, and the better the fit, the low-frequency amplitude of the frequency response curve will tend to rise.

[0059] from Figure 2 It can be seen that the ratio of the low-frequency amplitude to the intermediate-frequency amplitude is different for different fitting states. For example, for low frequencies (100Hz-700Hz) and intermediate frequencies (700Hz-1200hz), the tighter the earphone fits the ear canal, the greater the ratio of the low-frequency amplitude to the intermediate-frequency amplitude, and vice versa. Therefore, the embodiment of the present application can detect the fitting state of the earphone and the ear canal based on the ratio of the low-frequency amplitude to the intermediate-frequency amplitude. Specifically, the amplitude of the frequency domain transfer function is calculated as shown in the following formula (8):

[0060]

[0061] In one embodiment of the present application, detecting the fit state of the earphone and the ear canal of the human ear based on the ratio of the average value of the low-frequency amplitude to the average value of the medium-frequency amplitude includes: comparing the ratio of the average value of the low-frequency amplitude to the average value of the medium-frequency amplitude with a preset threshold; based on the comparison result, determining the fit state of the earphone and the ear canal of the human ear.

[0062] Specifically, the embodiment of the present application can detect the fit between the earphone and the human ear canal according to the ratio of the average value of the low-frequency amplitude to the average value of the intermediate frequency amplitude. For example, the calculation method of the ratio Ratio of the average value of the low-frequency amplitude to the average value of the intermediate frequency amplitude can be shown in the following formula (9):

[0063]

[0064] Among them, the low frequency band takes the bin (frequency point) value range as [6,45] as an example, then It can represent the average value of the low-frequency amplitude. For example, the mid-frequency band takes the bin (frequency point) value range as [57,128]. It can represent the average value of the intermediate frequency amplitude.

[0065] According to the size of the Ratio, the fit between the earphone and the human ear canal can be divided into different fit states. The embodiment of the present application provides the following four fit states: if the Ratio is greater than 1.7, it means that the fit is very close, and the fit state WearStatus1 is output; otherwise, if the Ratio is greater than 1.3, it means that the fit is relatively close, and the fit state WearStatus2 is output; otherwise, if the Ratio is greater than 0.8, it means that the fit is not close enough, and the fit state WearStatus3 is output; otherwise, if the Ratio is not greater than 0.8, it means that the fit is very loose, and the fit state WearStatus4 is output.

[0066] Of course, it should be noted that the four fitting states listed in the above embodiment are only for the convenience of understanding of the embodiment. In actual application scenarios, the fitting states can also be divided into only two fitting states: tight state and loose state. The specific division can be flexibly arranged by technical personnel in this field according to actual needs, and no specific limitation is made here.

[0067] After the fit state of the earphone and the ear canal of the human ear is detected according to the amplitude of the frequency domain transfer function, step S140 is executed, that is, according to the fit state of the earphone and the ear canal of the human ear, the corresponding active noise reduction filter is adaptively selected to perform active noise reduction through the active noise reduction filter. A person skilled in the art can understand that the selection of the active noise reduction filter here can specifically be: adaptively selecting an active noise reduction filter with a preset amplitude-frequency response (the preset amplitude-frequency response corresponds to the preset parameters of the active noise reduction filter), or adaptively using preset parameters to set the active noise reduction filter so that the active noise reduction filter has a preset amplitude-frequency response. A person skilled in the art can also understand that the active noise reduction filter here can be a feedback filter, a feedforward filter, or a combination of the two.

[0068] Specifically, in one embodiment of the present application, adaptively selecting a corresponding active noise reduction filter according to the fit state between the earphone and the ear canal of the human ear includes: if the fit state between the earphone and the ear canal of the human ear is tight, adaptively selecting an active noise reduction filter with a lower amplitude-frequency response; if the fit state between the earphone and the ear canal of the human ear is loose, adaptively selecting an active noise reduction filter with a higher amplitude-frequency response.

[0069] It is easy to understand that the fitting state can be divided into two, four or more levels, and an active noise reduction filter with a preset amplitude-frequency response corresponding to each level can be set respectively, and the selection can be adaptively made according to the currently judged fitting state level to achieve a more refined adaptive adjustment effect.

[0070] In addition to the above-mentioned embodiment of determining the bonding state based on the frequency domain transfer function, another specific implementation scheme can also be used, that is, a method for estimating using a time domain transfer function, which mainly includes the following steps:

[0071] (1) Obtain the audio processing signal of the current frame. One signal is the source audio signal sequence input to the speaker (without considering the complement of the filter), denoted by x = [x(0), x(1), ..., x(N-1)], and the other signal is the feedback audio signal sequence collected by the microphone, denoted by y = x1 + v = [x1(0), x1(1), ..., x1(N-1)] + [v(0), v(1), ..., v(N-1)], where x1 represents the audio signal played by the speaker collected by the microphone, and v represents the external interference noise collected by the microphone. Then, the two signal sequences are high-pass filtered to filter out the influence of the DC signal.

[0072] (2) Calculate the normalized autocorrelation sequence r of the source audio signal xx (l), and calculating the normalized cross-correlation sequence r between the feedback audio signal and the source audio signal yx (l) can be calculated as follows:

[0073]

[0074]

[0075] Where l is the length of the signal, μ v ,μ x They represent the statistical means of the external noise and the source audio signal respectively. Assuming that the external noise and the source audio signal are signals with a statistical mean of 0, then μ v =0,μ x = 0, the cross-correlation of two independent and irrelevant signals satisfies r vx ≈μ v μ x=0, so the cross-correlation mainly includes the relevant information of the two signals and has a suppressive effect on irrelevant information.

[0076] (3) For a system, according to the minimum mean square error criterion of the optimal coefficient, the cross-correlation r between the output and the input is yx (l), can be obtained by the autocorrelation of the input signal r xx The convolution of (l) and the system transfer function h(l) gives the following relationship:

[0077]

[0078] It can be seen from the above formula that the system time domain transfer function can be calculated based on the autocorrelation and cross-correlation, and the filter coefficient of the time domain transfer function can be estimated as:

[0079]

[0080] Where h' represents the coefficient vector, represents the N×N Toeplitz matrix, The element is γ yx (l) is the N×1 cross-correlation vector.

[0081] From the calculation formula of the system's time domain transfer function, it can be found that the time domain transfer function contains cross-correlation information. Cross-correlation mainly contains the relevant information of the two signals, and has a suppressive effect on irrelevant information. Therefore, like the frequency domain transfer function, the time domain transfer function can also effectively suppress the interference of external noise. In addition, the time domain transfer function also represents the information of the acoustic system itself, and has no specific requirements for the audio source.

[0082] (4) The wearing status is distinguished by using the Euclidean distance between the time domain transfer function and the target transfer function. d , that is, the transfer function corresponding to the case where the earphone and the ear canal are well coupled. The target transfer function can be obtained in the following ways: the target transfer function can be obtained by statistically analyzing the corresponding transfer functions of a large number of different people wearing the earphone tightly; or the transfer function obtained when the earphone is well sealed with the ear canal simulator is used as the target transfer function. Calculate the time domain transfer function h' and the target transfer function h dAt each signal sequence sampling point, if the Euclidean distance d is less than the distance threshold TH, the earphone is considered to be tightly fitted at this time, and the output flag is 1; otherwise, the earphone is considered to be loosely fitted at this time, and the output flag is 0. It is easy to understand that the fit state can also be divided into four or more levels based on the Euclidean distance, and an active noise reduction filter with a preset amplitude-frequency response corresponding to each level is set respectively, and the selection is adaptively performed according to the currently judged fit state level to achieve a more refined adaptive adjustment effect.

[0083] The above steps (1) to (4) can be used to effectively detect the wearing fit of the earphones, and select a suitable active noise reduction filter based on the detection results.

[0084] The principle of active noise reduction is to generate a signal after passing through the active noise reduction filter. This signal has the opposite phase and the same amplitude as the external interference noise signal leaked into the ear canal, thereby offsetting the external interference noise in the ear canal and playing a noise reduction role.

[0085] The embodiment of the present application selects an active noise reduction filter according to the fit between the earphone and the ear canal of the human ear based on the following principle: if the fit is looser, the sealing between the earphone and the ear canal of the human ear is worse, and the external interference noise leaking into the ear canal is more and larger in amplitude. At this time, to offset these external interference noises, it is necessary to select an active noise reduction filter that can generate a reverse signal with a larger amplitude. On the contrary, if the fit is tighter, the external interference noise entering the ear canal is relatively less. At this time, to offset these external interference noises, it is sufficient to select an active noise reduction filter that can generate a reverse signal with a smaller amplitude.

[0086] like Figure 3 As shown, a schematic diagram of the selection process of the active noise reduction filter according to an embodiment of the present application is provided. Specifically, Figure 3 The following table gives the selection of active noise reduction filters corresponding to the four fitting states. If the fitting state is WearStatus1, it means that the earphone and the human ear canal fit tightly enough, and the external interference noise leaked into the ear canal is very small. At this time, you can select an active noise reduction filter with a smaller amplitude-frequency response; if the fitting state is WearStatus2, it means that the earphone and the human ear canal fit closely, but the external interference noise leaked into the ear canal increases slightly. At this time, you can select an active noise reduction filter with a slightly smaller amplitude-frequency response; if the fitting state is WearStatus3, it means that the external interference noise leaked into the ear canal is large. At this time, you can select an active noise reduction filter with a slightly larger amplitude-frequency response; if the fitting state is WearStatus4, it means that the external interference noise leaked into the ear canal is very large. At this time, you can select an active noise reduction filter with a larger amplitude-frequency response.

[0087] In another embodiment of the present application, adaptively selecting a corresponding active noise reduction filter according to the fit state of the earphone and the human ear canal includes: obtaining a preset comparison table, wherein the preset comparison table stores a correspondence between the fit state and the amplitude-frequency response of the active noise reduction filter; and selecting, according to the fit state of the earphone and the human ear canal, an active noise reduction filter whose amplitude-frequency response corresponds to the fit state in the preset comparison table.

[0088] Different fitting states of the embodiments of the present application can be pre-set with corresponding active noise reduction filters, that is, a correspondence between different fitting states and the amplitude-frequency responses of different active noise reduction filters can be established in advance, and then the correspondence can be stored in a preset comparison table to facilitate subsequent query and selection.

[0089] The selection method of the active noise reduction filter can be adaptively switched according to the different detected fitting states. For example, when the detected fitting state is WearStatus1, the active noise reduction filter A1 with an amplitude-frequency response corresponding to WearStatus1 can be queried from the above preset comparison table, so as to use the active noise reduction filter A1 for active noise reduction. If it is subsequently detected that the fitting state has changed to WearStatus2, the active noise reduction filter A2 with an amplitude-frequency response corresponding to WearStatus2 can be queried from the above preset comparison table, and the current active noise reduction filter is switched from A1 to A2, thereby achieving the purpose of adaptively matching the corresponding active noise reduction filter according to the fitting state, so that the user can feel a good noise reduction effect in different headphone wearing conditions, thereby improving the user experience.

[0090] It should be noted that the detection frequency of the embodiment of the present application for the fit state of the earphone and the human ear canal can be real-time detection or detection can be performed at regular intervals. The specific setting of the detection frequency can be flexibly set by technical personnel in this field according to actual conditions and is not specifically limited here.

[0091] In one embodiment of the present application, the active noise reduction filter includes a feedback noise reduction filter and a feedforward noise reduction filter.

[0092] The active noise reduction filter in the embodiment of the present application may include a feedback noise reduction filter and a feedforward noise reduction filter, so the above preset comparison table may store in advance the feedforward noise reduction filters and feedback noise reduction filters corresponding to different fitting states.

[0093] In actual application scenarios, if the headset is only provided with a feedback noise reduction filter, then after the fit state is detected, the feedback noise reduction filter corresponding to the fit state can be directly turned on; and if the headset is provided with both a feedforward noise reduction filter and a feedback noise reduction filter, then after the fit state is detected, the feedforward noise reduction filter and the feedback noise reduction filter corresponding to the fit state can be turned on at the same time. In other words, the embodiment of the present application can select the active noise reduction filter to be turned on according to the actual setting of the active noise reduction filter of the headset.

[0094] In one embodiment of the present application, adaptively selecting a corresponding active noise reduction filter according to the fit state of the earphone and the ear canal of a human ear includes: adaptively setting parameters of the active noise reduction filter.

[0095] The preset parameters of the active noise reduction filter corresponding to different fitting states can be obtained through empirical measurement, taking the following measurement method as an example:

[0096] A group of test subjects are selected, and for each test subject, the optimal feedback noise reduction filter and the optimal feedforward noise reduction filter under four fitting states are tested. After all the tests are completed, for each fitting state, the average value of the optimal feedforward noise reduction filter parameters measured by multiple test subjects is used as the feedforward noise reduction filter under this fitting state. Similarly, the average value of the optimal feedback noise reduction filter parameters measured by multiple test subjects is used as the feedback noise reduction filter under this fitting state.

[0097] The measurement and calculation of the feedback noise reduction filter is based on the following principle: Since the specified feedback noise reduction function has a corresponding unique open-loop response function L, and the open-loop response is the multiplication of two parts: the feedback noise reduction filter response and the speaker-feedback microphone frequency response, the feedback noise reduction filter response is the unique open-loop response divided by the speaker-feedback microphone frequency response. In practical applications, the open-loop response when wearing well can be used as the unique open-loop response function L.

[0098] When the person under test and the fitting state are determined, the measurement and calculation process of the feedback noise reduction filter is as follows: measure the speaker-feedback microphone frequency response under different fitting states as the divisor, and the aforementioned unique open-loop response as the dividend, so as to obtain the frequency response of the feedback noise reduction filter. According to the frequency response of the feedback noise reduction filter, a frequency domain-time domain inverse Fourier transform can be performed to obtain a feedback noise reduction filter in the form of FIR (Finite Impulse Response filter). It is also possible to directly obtain an IIR (Infinite Impulse Response filter) feedback noise reduction filter based on this frequency response. In actual application scenarios, either FIR or IIR can be selected.

[0099] The measurement and calculation of the feedforward noise reduction filter is based on the following principle: assuming that the transfer function of the noise from the feedforward microphone to the ear is P, then the feedforward noise reduction filter is the transfer function P of the noise from the ear divided by the frequency response Gf from the speaker to the ear.

[0100] When the person under test and the fitting state are determined, the measurement and calculation process of the feedforward noise reduction filter is as follows: noise is generated outside the earphone, and the transfer function P from the noise at the feedforward microphone to the noise inside the ear is measured and used as the dividend, as well as the frequency response Gf from the speaker to the ear at this time, which is used as the divisor. Division calculation is performed to obtain the frequency response of the feedforward noise reduction filter. After obtaining this frequency response, a frequency domain-time domain inverse Fourier transform can be performed to obtain a feedforward noise reduction filter in FIR form, or an IIR form of feedforward noise reduction filter can be directly obtained based on this frequency response. In actual application scenarios, either FIR or IIR can be selected.

[0101] Due to physical properties, the amplitude-frequency response of feedback noise reduction filters and feedforward noise reduction filters will have the characteristics that the more external interference noise leaks into the ear canal, the higher the amplitude-frequency response of the low-frequency amplitude.

[0102] For the feedback noise reduction filter, because the open-loop response is unique, and the feedback noise reduction filter is the open-loop response divided by the speaker-feedback microphone transfer function, when the external interference noise leaking into the ear canal increases, the low-frequency amplitude in the transfer function between the speaker and the feedback microphone will be attenuated more, and accordingly, the amplitude of the feedback noise reduction filter will be raised, that is, the amplitude-frequency response of the selected feedback noise reduction filter in the low-frequency band will be larger. When the external interference noise leaking into the ear canal decreases, the low-frequency amplitude in the transfer function between the speaker and the feedback microphone will be attenuated very little, and accordingly, the amplitude-frequency response of the selected feedback noise reduction filter in the low-frequency band will be smaller.

[0103] For the feedforward noise reduction filter, when the external interference noise leaking into the ear canal increases, the frequency response Gf from the speaker to the ear will be attenuated more at low frequencies, and the transfer function P from the noise at the feedforward microphone to the noise in the ear will increase in the full frequency range, so the amplitude-frequency response P / Gf of the feedforward noise reduction filter will increase. When the external interference noise leaking into the ear canal decreases, the frequency response Gf from the speaker to the ear will be attenuated very little at low frequencies, and the transfer function P from the noise at the feedforward microphone to the noise in the ear will decrease in the full frequency range, so the amplitude-frequency response P / Gf of the feedforward noise reduction filter will decrease.

[0104] like Figure 4 As shown, a flowchart of active noise reduction of headphones according to an embodiment of the present application is provided, which mainly includes the following parts:

[0105] (1) Audio signal acquisition: acquiring the source audio signal input to the speaker and the feedback audio signal collected by the microphone;

[0106] (2) Fitting state detection: The fitting state is detected using the source audio signal input to the speaker and the feedback audio signal collected by the microphone. First, the obtained source audio signal and feedback audio signal are transformed into the frequency domain for processing; then the auto-power spectrum of the source audio signal and the cross-power spectrum of the feedback audio signal and the source audio signal are calculated using the periodogram method or other spectrum estimation methods, such as the parameter spectrum estimation method. Then, the frequency domain transfer function is calculated using the auto-power spectrum of the source audio signal and the cross-power spectrum of the feedback audio signal and the source audio signal.

[0107] (3) Fitting status output: Different fitting status are determined according to the ratio of the average value of the low-frequency amplitude and the medium-frequency amplitude in the frequency domain transfer function.

[0108] (4) Selection of active noise reduction filter: Automatically match the corresponding active noise reduction filter according to the detected fit state. Under the same background noise environment, the tighter the fit, the smaller the amplitude of the reverse signal generated by the selected active noise reduction filter, and vice versa.

[0109] Through the above-mentioned headphone active noise reduction process, the purpose of adaptively matching the corresponding active noise reduction filter according to the fitting state is achieved, so that users can feel a good noise reduction effect in different headphone wearing conditions, thereby improving the user experience.

[0110] The embodiment of the present application also provides a headphone active noise reduction device, which belongs to the same technical concept as the aforementioned headphone active noise reduction method. Figure 5 A schematic diagram of the structure of an active noise reduction device for headphones according to an embodiment of the present application is shown. Figure 5 The headset includes a speaker and a microphone for collecting audio signals played by the speaker. The headset active noise reduction device 500 includes: an audio signal acquisition unit 510, a transfer function determination unit 520, a fitting state determination unit 530 and an active noise reduction unit 540. Among them,

[0111] The audio signal acquisition unit 510 is used to acquire the source audio signal input to the speaker and the feedback audio signal collected by the microphone;

[0112] A transfer function determination unit 520, configured to determine a transfer function according to a source audio signal and a feedback audio signal;

[0113] A fitting state determining unit 530, configured to determine a fitting state between the earphone and the ear canal of a human ear according to a transfer function;

[0114] The active noise reduction unit 540 is used to adaptively select a corresponding active noise reduction filter according to the fit state of the earphone and the human ear canal, so as to perform active noise reduction through the active noise reduction filter.

[0115] In one embodiment of the present application, the transfer function determination unit 520 is specifically used to: calculate the autopower spectrum of the source audio signal and the cross-power spectrum of the feedback audio signal and the source audio signal using a preset power spectrum estimation method; smooth the autopower spectrum and the cross-power spectrum within a preset time period, respectively, to obtain an average autopower spectrum and an average cross-power spectrum; and determine the transfer function based on the ratio of the average cross-power spectrum to the average autopower spectrum.

[0116] In one embodiment of the present application, the fit state determination unit 530 is specifically used to: determine the average value of the low-frequency amplitude and the average value of the intermediate frequency amplitude in the transfer function; and detect the fit state of the earphone and the human ear canal based on the ratio of the average value of the low-frequency amplitude to the average value of the intermediate frequency amplitude.

[0117] For example, the ratio of the average value of the low-frequency amplitude to the average value of the mid-frequency amplitude is compared with a preset threshold; based on the comparison result, the fit state of the earphone and the human ear canal is determined.

[0118] In one embodiment of the present application, the active noise reduction unit 540 is specifically used to: if the earphone is in a tight fit with the ear canal of the human ear, adaptively select an active noise reduction filter with a lower amplitude-frequency response; if the earphone is in a loose fit with the ear canal of the human ear, adaptively select an active noise reduction filter with a higher amplitude-frequency response.

[0119] In another embodiment of the present application, the active noise reduction unit 540 is specifically used to: obtain a preset comparison table, wherein the preset comparison table stores the correspondence between the fitting state and the amplitude-frequency response of the active noise reduction filter; and select, in the preset comparison table, an active noise reduction filter whose amplitude-frequency response corresponds to the fitting state according to the fitting state of the earphone and the human ear canal.

[0120] In one embodiment of the present application, the active noise reduction filter includes a feedback noise reduction filter and a feedforward noise reduction filter.

[0121] In one embodiment of the present application, the active noise reduction unit 540 is specifically used to: adaptively set parameters of the active noise reduction filter.

[0122] In one embodiment of the present application, the transfer function is a time domain transfer function.

[0123] In one embodiment of the present application, the transfer function determination unit 520 is specifically used to: perform high-pass filtering on the source audio signal and the feedback audio signal respectively; obtain a normalized autocorrelation sequence of the source audio signal according to the high-pass filtered source audio signal and the high-pass filtered feedback audio signal, and obtain a normalized mutual correlation sequence of the source audio signal and the feedback audio signal; obtain a time domain transfer function according to a minimum mean square error criterion and using the normalized autocorrelation sequence and the normalized mutual correlation sequence.

[0124] In one embodiment of the present application, the fit state determination unit 530 is specifically used to: obtain the Euclidean distance between the time domain transfer function and the predetermined target transfer function at each signal sequence sampling point; and determine the fit state of the earphone and the human ear canal based on the Euclidean distance.

[0125] It should be noted that:

[0126] Figure 6 The schematic diagram of the structure of active noise reduction headphones is shown. Please refer to Figure 6 At the hardware level, the active noise reduction headset includes a speaker, a microphone for collecting sound signals in the ear canal, a processor, a memory for storing computer executable instructions, and optionally an interface module, a communication module, etc. The memory may include a memory, such as a high-speed random access memory (RAM), and may also include a non-volatile memory (non-volatile memory), such as at least one disk storage, etc. Of course, the active noise reduction headset may also include hardware required for other services.

[0127] The processor, speaker, microphone and memory can be connected to each other through an internal bus, which can be an ISA (Industry Standard Architecture) bus, a PCI (Peripheral Component Interconnect) bus or an EISA (Extended Industry Standard Architecture) bus. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 6 Only one bidirectional arrow is used in the diagram, but this does not mean that there is only one bus or only one type of bus.

[0128] The memory is used to store computer executable instructions. The memory provides computer executable instructions to the processor through an internal bus.

[0129] The processor executes the computer executable instructions stored in the memory and is specifically used to implement the following operations:

[0130] Obtaining the source audio signal input to the speaker and the feedback audio signal collected by the microphone;

[0131] determining a transfer function based on the source audio signal and the feedback audio signal;

[0132] Determine the fit between the earphone and the ear canal of the human ear according to the transfer function;

[0133] According to the fit between the earphone and the human ear canal, the corresponding active noise reduction filter is adaptively selected to perform active noise reduction through the active noise reduction filter.

[0134] The above application Figure 5 The functions performed by the headphone active noise reduction device disclosed in the illustrated embodiment can be applied to a processor or implemented by a processor. The processor may be an integrated circuit chip with signal processing capabilities. Figure 1 Each step of the headphone active noise reduction method disclosed in the illustrated embodiment can be completed by an integrated logic circuit of hardware in a processor or by instructions in the form of software. The above-mentioned processor can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components. The methods, steps and logic block diagrams disclosed in the embodiments of the present application can be implemented or executed. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor, etc. The steps of the method disclosed in the embodiments of the present application can be directly embodied as being executed by a hardware decoding processor, or can be executed by a combination of hardware and software modules in a decoding processor. The software module can be located in a mature storage medium in the field such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory or an electrically erasable programmable memory, a register, etc. The storage medium is located in a memory, and the processor reads the information in the memory and completes the steps of the above method in combination with its hardware.

[0135] The embodiment of the present application further proposes a computer-readable storage medium, which stores one or more programs. When the one or more programs are executed by a processor, the aforementioned headphone active noise reduction method is implemented, and is specifically used to execute:

[0136] Obtaining the source audio signal input to the speaker and the feedback audio signal collected by the microphone;

[0137] determining a transfer function based on the source audio signal and the feedback audio signal;

[0138] Determine the fit between the earphone and the ear canal of the human ear according to the transfer function;

[0139] According to the fit between the earphone and the human ear canal, the corresponding active noise reduction filter is adaptively selected to perform active noise reduction through the active noise reduction filter.

[0140] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program codes.

[0141] The present application is described by flowcharts and / or block diagrams of the methods, devices (systems), and computer program products of the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0142] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0143] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1The steps for the functions specified in one or more boxes.

[0144] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0145] The memory may include non-permanent storage in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0146] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0147] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0148] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) characterized in that it contains computer-usable program code.

[0149] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A method for active noise reduction of headphones, the headphones comprising a speaker and a microphone for collecting sound signals in the ear canal, characterized in that: The method comprises: Acquire a source audio signal input to the speaker and a feedback audio signal collected by the microphone; determining a transfer function based on the source audio signal and the feedback audio signal; Determining the fitting state between the earphone and the ear canal of a human ear according to the transfer function; Adaptively selecting a corresponding active noise reduction filter according to the fit state of the earphone and the ear canal of a human ear, so as to perform active noise reduction through the active noise reduction filter; Wherein, when the transfer function is a frequency domain transfer function, determining the fitting state of the earphone and the ear canal of a human ear according to the transfer function includes: Determine an average value of the low-frequency amplitude and an average value of the intermediate-frequency amplitude in the transfer function; detect the fit state of the earphone and the ear canal of a human ear according to the ratio of the average value of the low-frequency amplitude to the average value of the intermediate-frequency amplitude; The adaptively selecting a corresponding active noise reduction filter according to the fit state between the earphone and the ear canal of the human ear comprises: If the earphone fits tightly to the ear canal of the human ear, an active noise reduction filter with a lower amplitude-frequency response is adaptively selected; if the earphone fits loosely to the ear canal of the human ear, an active noise reduction filter with a higher amplitude-frequency response is adaptively selected.

2. The method according to claim 1, characterized in that Determining the transfer function according to the source audio signal and the feedback audio signal comprises: Calculating the autopower spectrum of the source audio signal and the cross-power spectrum between the feedback audio signal and the source audio signal by using a preset power spectrum estimation method; Smoothing the auto-power spectrum and the cross-power spectrum within a preset time period to obtain an average auto-power spectrum and an average cross-power spectrum; The transfer function is determined according to a ratio of the average cross power spectrum to the average auto power spectrum.

3. The method according to claim 1, characterized in that The detecting the fitting state of the earphone and the ear canal of a human ear according to the ratio of the average value of the low-frequency amplitude to the average value of the intermediate-frequency amplitude comprises: Comparing the ratio of the average value of the low frequency amplitude to the average value of the medium frequency amplitude with a preset threshold; Based on the comparison result, the fit state of the earphone and the ear canal of the human ear is determined.

4. The method according to claim 1, characterized in that: The adaptively selecting a corresponding active noise reduction filter according to the fit state between the earphone and the ear canal of the human ear comprises: Obtaining a preset comparison table, wherein the preset comparison table stores a correspondence between the fitting state and the amplitude-frequency response of the active noise reduction filter; According to the fitting state of the earphone and the ear canal of the human ear, an active noise reduction filter having an amplitude-frequency response corresponding to the fitting state is selected from the preset comparison table.

5. The method according to claim 1, wherein: The active noise reduction filter includes a feedback noise reduction filter and a feedforward noise reduction filter.

6. The method according to claim 1 or 5, wherein: Adaptively selecting a corresponding active noise reduction filter according to the fit state between the earphone and the ear canal of a human ear includes: The parameters of the active noise reduction filter are adaptively set. The method of claim 1 , wherein the transfer function is a time domain transfer function.

8. The method according to claim 7, wherein: Determining the transfer function according to the source audio signal and the feedback audio signal comprises: Performing high-pass filtering on the source audio signal and the feedback audio signal respectively; Obtaining a normalized autocorrelation sequence of the source audio signal according to the high-pass filtered source audio signal and the high-pass filtered feedback audio signal, and obtaining a normalized cross-correlation sequence of the source audio signal and the feedback audio signal; The time domain transfer function is obtained according to a minimum mean square error criterion and by using the normalized autocorrelation sequence and the normalized cross-correlation sequence.

9. The method according to claim 8, wherein: Determining the fitting state between the earphone and the ear canal of a human ear according to the transfer function includes: Obtaining the Euclidean distance between the time domain transfer function and a predetermined target transfer function at each signal sequence sampling point; The fitting state of the earphone and the ear canal of the human ear is determined based on the Euclidean distance.

10. An active noise reduction device for headphones, the headphones comprising a speaker and a microphone for collecting audio signals played by the speaker, characterized in that: The device comprises: An audio signal acquisition unit, used to acquire a source audio signal input to the speaker and a feedback audio signal collected by the microphone; a transfer function determining unit, configured to determine a transfer function according to the source audio signal and the feedback audio signal; A fitting state determining unit is used to determine the fitting state of the earphone and the ear canal of the human ear according to the transfer function, wherein when the transfer function is a frequency domain transfer function, determining the fitting state of the earphone and the ear canal of the human ear according to the transfer function includes: determining an average value of low frequency amplitudes and an average value of medium frequency amplitudes in the transfer function; Detecting the fit between the earphone and the ear canal of a human ear according to the ratio of the average value of the low-frequency amplitude to the average value of the intermediate-frequency amplitude; The active noise reduction unit is used to adaptively select a corresponding active noise reduction filter according to the fit state between the earphone and the ear canal of the human ear, so as to perform active noise reduction through the active noise reduction filter; specifically, if the fit state between the earphone and the ear canal of the human ear is a tight state, then adaptively select an active noise reduction filter with a lower amplitude-frequency response; if the fit state between the earphone and the ear canal of the human ear is not a loose state, then adaptively select an active noise reduction filter with a higher amplitude-frequency response.

11. An active noise reduction headset, characterized in that: It includes: a speaker, a microphone for collecting sound signals in the ear canal, a processor, and a memory for storing computer executable instructions. When the computer executable instructions are executed by the processor, the active noise reduction method for headphones according to any one of claims 1 to 9 is implemented.

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