CN115250396A - Active noise reduction method and device for earphone and active noise reduction earphone - Google Patents
Active noise reduction method and device for earphone and active noise reduction earphone Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R1/00—Details of transducers, loudspeakers or microphones
- H04R1/10—Earpieces; Attachments therefor ; Earphones; Monophonic headphones
- H04R1/1083—Reduction of ambient noise
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
- G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
- G10K11/1781—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase characterised by the analysis of input or output signals, e.g. frequency range, modes, transfer functions
- G10K11/17813—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase characterised by the analysis of input or output signals, e.g. frequency range, modes, transfer functions characterised by the analysis of the acoustic paths, e.g. estimating, calibrating or testing of transfer functions or cross-terms
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
- G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
- G10K11/1785—Methods, e.g. algorithms; Devices
- G10K11/17853—Methods, e.g. algorithms; Devices of the filter
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
- G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
- G10K11/1787—General system configurations
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
- G10K2210/10—Applications
- G10K2210/108—Communication systems, e.g. where useful sound is kept and noise is cancelled
- G10K2210/1081—Earphones, e.g. for telephones, ear protectors or headsets
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
- G10K2210/30—Means
- G10K2210/301—Computational
- G10K2210/3023—Estimation of noise, e.g. on error signals
- G10K2210/30232—Transfer functions, e.g. impulse response
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
- G10K2210/30—Means
- G10K2210/301—Computational
- G10K2210/3028—Filtering, e.g. Kalman filters or special analogue or digital filters
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2460/00—Details of hearing devices, i.e. of ear- or headphones covered by H04R1/10 or H04R5/033 but not provided for in any of their subgroups, or of hearing aids covered by H04R25/00 but not provided for in any of its subgroups
- H04R2460/01—Hearing devices using active noise cancellation
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Abstract
The application discloses an active noise reduction method and device for an earphone and an active noise reduction earphone. The headset comprising a speaker and a microphone for collecting sound signals within the ear canal, the method comprising: acquiring a source audio signal input to the loudspeaker and a feedback audio signal collected by the microphone; determining a transfer function from the source audio signal and the feedback audio signal; determining the fitting state of the earphone and the ear canal of the human ear according to the transfer function; and according to the fitting state of the earphone and the ear canal of the human ear, adaptively selecting a corresponding active noise reduction filter so as to actively reduce noise through the active noise reduction filter. The active noise reduction method of the earphone achieves the purpose of adaptively matching the corresponding active noise reduction filter according to the fitting state, so that a user can feel good noise reduction effect under different earphone wearing conditions, and the use experience of the user is improved.
Description
Technical Field
The application relates to the technical field of earphones, in particular to an earphone active noise reduction method and device and an active noise reduction earphone.
Background
The earphone has been widely used in daily life due to its small size and portability. In addition to listening to music, watching video, etc. with headphones, the headphones also function to isolate noise, providing a quiet environment for the user. The traditional earphone has limitations on physical isolation of mid-low frequency Noise, so that an Active Noise Cancellation (ANC) technology is more applied to earphones.
The principle of active noise reduction is to generate a signal with a similar amplitude and an opposite phase to the external interference noise to counteract the influence of the external interference noise.
The existing active noise reduction earphone generally realizes the noise reduction function through an active noise reduction filter which is arranged in the earphone in advance. However, the difference of the wearing fit states among the individual users is neglected in the method, so that different users feel different noise reduction effects in the same noise environment, and the noise reduction requirements of different users cannot be met.
Disclosure of Invention
In view of this, the present application mainly aims to provide an active noise reduction method and apparatus for an earphone, and an active noise reduction earphone, so as to solve the technical problem that the existing active noise reduction earphone cannot meet noise reduction requirements of different users.
According to a first aspect of the present application, there is provided an active noise reduction method for an earphone, the earphone comprising a speaker and a microphone for collecting sound signals in an ear canal, the method comprising:
acquiring a source audio signal input to the loudspeaker and a feedback audio signal collected by the microphone;
determining a transfer function from the source audio signal and the feedback audio signal;
determining the fitting state of the earphone and the ear canal of the human ear according to the transfer function;
and according to the fitting state of the earphone and the ear canal of the human ear, a corresponding active noise reduction filter is selected in a self-adaptive manner, so that active noise reduction is carried out through the active noise reduction filter.
According to a second aspect of the present application, there is provided an active noise reduction device for a headphone, the headphone comprising a speaker and a microphone for collecting an audio signal played by the speaker, the device comprising:
the audio signal acquisition unit is used for acquiring a source audio signal input to the loudspeaker and a feedback audio signal acquired by the microphone;
a transfer function determination unit for determining a transfer function from the source audio signal and the feedback audio signal;
the fit state determining unit is used for determining the fit state of the earphone and the ear canal of the human ear according to the transfer function;
and the active noise reduction unit is used for adaptively selecting a corresponding active noise reduction filter according to the fitting state of the earphone and the ear canal of the human ear so as to actively reduce noise through the active noise reduction filter.
In accordance with a third aspect of the present application, there is provided an active noise reduction headphone comprising: a speaker, a microphone for collecting sound signals within the ear canal, a processor, a memory storing computer executable instructions,
the computer executable instructions, when executed by the processor, implement any one of the foregoing methods for active noise reduction for headphones.
According to a fourth aspect of the present application, there is provided a computer readable storage medium storing one or more programs which, when executed by a processor, implement any of the aforementioned methods of active noise reduction for headphones.
The beneficial effect of this application is: according to the earphone active noise reduction method, the bonding state detection is carried out according to the loudspeaker in the earphone and the microphone used for collecting the sound signals in the auditory canal, and then the appropriate active noise reduction filter is selected in a self-adaptive mode according to the bonding state detection result and used for active noise reduction. The active noise reduction method for the earphone achieves the effect of good noise reduction aiming at different wearing conditions of different users under the same noise environment, and meets the noise reduction requirements of different users.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the application. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:
fig. 1 is a schematic flowchart of an active noise reduction method for a headphone according to an embodiment of the present application;
FIG. 2 is a schematic diagram of a frequency response curve of a frequency domain transfer function in different fitting states according to an embodiment of the present disclosure;
FIG. 3 is a schematic diagram illustrating a selection process of an active noise reduction filter according to an embodiment of the present application;
fig. 4 is a block diagram illustrating an active noise reduction process of a headphone according to an embodiment of the present application;
fig. 5 is a schematic structural diagram of an active noise reduction device of a headphone according to an embodiment of the present application;
fig. 6 is a schematic structural diagram of an active noise reduction earphone according to an embodiment of the present application.
Detailed Description
Exemplary embodiments of the present application will be described in more detail below with reference to the accompanying drawings. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. While exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application may be embodied in various forms and should not be limited to the embodiments set forth herein.
Typically, active noise reduction earphones are required to work with a good seal of the ear canal. Because the structure of the human ear is different, the wearing modes of different users are different, and in order to wear the comfort, some users may choose earmuffs with different sizes, so that the fitting degree of the earphone and the auditory canal of the human ear is different. Different fitting degrees are different, the noise entering the ears through the gaps between the earphones and the ear canals of the human ears is different, if the same noise reduction filter is adopted, the noise cancellation is less under the wearing condition probably due to different noise amplitudes, so that the same noise reduction filter is adopted under the same environment, and the generated noise reduction effect is different.
Based on this, fig. 1 shows a flowchart of an active noise reduction method of an earphone according to an embodiment of the present application, and referring to fig. 1, the earphone of the embodiment of the present application includes a speaker and a microphone for collecting sound signals in an ear canal, and the active noise reduction method of the earphone of the embodiment of the present application includes the following steps S110 to S140:
in step S110, a source audio signal input to the speaker and a feedback audio signal collected by the microphone are obtained.
Step S120, determining a transfer function according to the source audio signal and the feedback audio signal.
And step S130, determining the fitting state of the earphone and the ear canal of the human ear according to the transfer function.
And step S140, selecting a corresponding active noise reduction filter in a self-adaptive manner according to the fitting state of the earphone and the ear canal of the human ear, so as to carry out active noise reduction through the active noise reduction filter.
According to the active noise reduction method of the earphone, the bonding state detection is carried out according to the loudspeaker in the earphone and the microphone used for collecting the sound signals in the auditory canal, and then the proper active noise reduction filter is selected in a self-adaptive mode according to the detection result of the bonding state to carry out active noise reduction. The active noise reduction method of the earphone achieves the effect of good noise reduction aiming at different wearing conditions of different users under the same noise environment, and meets the noise reduction requirements of different users.
The above steps S110 to S140 will be described in detail with reference to fig. 1 to 4.
Those skilled in the art will readily appreciate that the transfer function may be a frequency domain transfer function or a time domain transfer function in accordance with various embodiments of the present invention. The following description is first made based on a specific example of the frequency domain transfer function.
First, step S110 is performed, i.e. a source audio signal input to the speaker and a feedback audio signal collected by the microphone are obtained.
In the embodiment of the application, two paths of signals are obtained together, one path of signal is a source audio signal sequence input to a speaker and is denoted as x = [ x (0), x (1),. ·., x (N-1) ], one path is a feedback audio signal sequence collected by a microphone and is denoted as y = x1+ v = [ x1 (0), x1 (1),... 9, x1 (N-1) ] + [ v (0), v (1),... V (1) ], where x1 represents a signal played by the speaker collected by the microphone and v represents external interference noise collected by the microphone. And then, carrying out high-pass filtering processing on the two paths of signal sequences to filter the influence of the direct current signal.
In order to reduce the error of frequency component estimation, the two paths of signals may be further respectively subjected to windowing and frequency domain transformation. Specifically, an analysis window, such as a hamming window (w = [ w (0), w (1),.. Times., w (N-1) ]), is added to each of the two signals, and fourier transform is performed to obtain frequency domain signals, which are respectively denoted as X (k), Y (k), as shown in the following equations (1) and (2):
where N represents the number of fourier transform points, N represents the signal sequence samples, and k represents the frequency bin (frequency point) ordinal number.
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, a frequency domain transfer function is determined according to the source audio signal and the feedback audio signal.
Specifically, in one embodiment of the present application, determining a frequency domain transfer function from a source audio signal and a feedback audio signal comprises: calculating the self-power spectrum of the source audio signal by using a preset power spectrum estimation method, and feeding back the cross-power spectrum of the audio signal and the source audio signal; respectively smoothing the self-power spectrum and the cross-power spectrum in a preset time period to obtain an average self-power spectrum and an average cross-power spectrum; and determining a frequency domain transfer function according to the ratio of the average cross-power spectrum to the average self-power spectrum.
First, calculating the self-power spectrum of the source audio signal and the cross-power spectrum of the feedback audio signal and the source audio signal, where a periodogram method may be used for power spectrum estimation, and of course, a person skilled in the art may select another type of spectrum estimation method according to actual needs, which is not limited specifically herein.
Taking the periodogram method as an example, the self-power spectrum Pxx (k) of the source audio signal is calculated as shown in the following formula (3):
the cross-power spectrum Pyx (k) of the feedback audio signal and the source audio signal is calculated as shown in the following formula (4):
where denotes the conjugate and E denotes the mathematical expectation. Since the external interference noise V is not coherent with the source audio signal X input to the speaker, there is E [ V (k) X * (k)]≈0。
In order to effectively eliminate the influence of uncorrelated components in the two signals, the embodiment of the application performs smoothing processing on the power spectrum. Specifically, the average of the power spectrum over a period of time is smoothed, for example, the time length LenT =30 frames, and then the average self-power spectrum pxvave (k) and the average cross-power spectrum PyxAve (k) are calculated as shown in the following equations (5) and (6):
after obtaining the average self-power spectrum pxvave (k) and the average cross-power spectrum PyxAve (k), obtaining a frequency domain transfer function H' (k) according to the ratio of the average cross-power spectrum PyxAve (k) to the average self-power spectrum pxvave (k), wherein the specific calculation mode is as shown in the following formula (7):
after determining the frequency domain transfer function 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.
Specifically, in one embodiment of the present application, detecting a fitting state of the earphone to the ear canal of the human ear according to the magnitude of the frequency domain transfer function includes: determining an average value of low-frequency amplitude and an average value of medium-frequency amplitude in the frequency domain transfer function; and detecting the fitting state of the earphone and the ear canal of the human ear according to the ratio of the average value of the low-frequency amplitude to the average value of the medium-frequency amplitude.
As shown in fig. 2, a schematic diagram of frequency response curves of frequency domain transfer functions in different fitting states according to an embodiment of the present application is provided. When the fitting degree of the earphone and the ear canal of the human ear is different, the low-frequency (100 Hz-700 Hz) amplitude leakage of the loudspeaker is different, and because the low-frequency amplitude leakage exists, the poorer the fitting state is, the lower the low-frequency amplitude is; conversely, the better the bonding state, the higher the low frequency amplitude. The response is on the frequency response curve of the frequency domain transfer function, that is, the worse the fitting state, the more the low-frequency amplitude of the frequency response curve is reduced, the better the fitting state is, and the tendency that the low-frequency amplitude of the frequency response curve is raised upwards is generated.
As can be seen from fig. 2, the ratio of the low frequency amplitude to the medium frequency amplitude is different for different fitting states, such as the low frequency (100 Hz-700 Hz) and the medium frequency (700 Hz-1200 Hz), and the tighter the fitting between the earphone and the ear canal of the human ear, the larger the ratio of the low frequency amplitude to the medium frequency amplitude, and the smaller the ratio of the low frequency amplitude to the medium frequency amplitude. Therefore, the embodiment of the application can detect the attaching state of the earphone and the ear canal of the human ear according to the ratio of the low-frequency amplitude to the medium-frequency amplitude. Specifically, the amplitude of the frequency domain transfer function is calculated as shown in the following equation (8):
in one embodiment of the present application, detecting the fitting state of the earphone and the ear canal of the human ear according to a ratio of an average value of the low frequency amplitude to an 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 result of the comparison, the fitting state of the earphone to the ear canal of the human ear is determined.
Specifically, the embodiment of the present application may detect the fitting condition between the earphone and the ear canal of the human ear according to the Ratio of the average value of the low frequency amplitude to the average value of the medium frequency amplitude, for example, the Ratio of the average value of the low frequency amplitude to the average value of the medium frequency amplitude may be calculated as shown in the following equation (9):
wherein the low frequency band has a bin value range of [6,45 ]]For example, then
Can represent the average value of low-frequency amplitude, and the intermediate frequency band has a bin value range of [57,128%]For example, then
The average value of the intermediate frequency amplitude can be represented.
According to the Ratio, the fitting conditions of the earphone and the ear canal of the human ear can be divided into different fitting states, and the following 4 fitting states are given in the embodiment of the application: if the Ratio is larger than 1.7, the lamination is very tight, and a lamination state Wearstatus1 is output; otherwise, if the Ratio is larger than 1.3, the lamination is tight, and a lamination state Wearstatus2 is output; otherwise, if the Ratio is larger than 0.8, the bonding is not tight enough, and a bonding state WeartStatus 3 is output; otherwise, if the Ratio is not greater than 0.8, the bonding is not tight enough, and the bonding state WeartStatus 4 is output.
It should be noted that, of course, the 4 attaching states listed in the above embodiment are only for facilitating understanding of the embodiment, and in an actual application scenario, the attaching states may be divided into only two attaching states, namely a tight state and a non-tight state, and how to divide the attaching states is specific, and a person skilled in the art may flexibly set the attaching states according to actual needs, and the attaching states are not limited specifically herein.
After detecting the fitting state of the earphone and the ear canal of the human ear according to the amplitude of the frequency domain transfer function, step S140 is performed, that is, a corresponding active noise reduction filter is adaptively selected according to the fitting state of the earphone and the ear canal of the human ear, so as to perform active noise reduction through the active noise reduction filter. Those skilled in the art will understand that the active noise reduction filter is selected here, and specifically, the active noise reduction filter may be: the method comprises the steps of adaptively selecting an active noise reduction filter with a preset amplitude-frequency response (the preset amplitude-frequency response corresponds to preset parameters of the active noise reduction filter), or adaptively setting the active noise reduction filter by using the preset parameters, so that the active noise reduction filter has the preset amplitude-frequency response. It will also be understood by those skilled in the art that the active noise reduction filter herein may be a feedback filter, a feedforward filter, or a combination of both.
Specifically, in one embodiment of the present application, adaptively selecting a corresponding active noise reduction filter according to a fitting state of an earphone and an ear canal of a human ear includes: if the fit state of the earphone and the ear canal of the human ear is a tight state, an active noise reduction filter with lower amplitude-frequency response is selected in a self-adaptive manner; and if the fit state of the earphone and the ear canal of the human ear is not a tight state, the active noise reduction filter with higher amplitude-frequency response is selected in a self-adaptive mode.
It is easy to understand that the fitting state can be divided into two, four or more levels, active noise reduction filters with preset amplitude-frequency response and corresponding to each level one to one are respectively arranged, and the selection is carried out in a self-adaptive manner according to the level of the currently judged fitting state, so as to achieve a finer self-adaptive adjustment effect.
Besides the foregoing embodiment of determining the fitting state based on the frequency-domain transfer function, the method for estimating by using the time-domain transfer function may also be based on another specific implementation, and mainly includes the following steps:
(1) An audio processing signal for the current frame is obtained. One path of signal is a source audio signal sequence input to a loudspeaker (without considering the supplement of a filter), and is recorded as x = [ x (0), x (1),. Once.. And x (N-1) ], and the other path of signal is a feedback audio signal sequence collected by a microphone, and is recorded as y = x1+ v = [ x1 (0), x1 (1),. Once.,. X1 (N-1) ] + [ v (0), v (1),. Once.,. V (N-1) ], wherein x1 represents an audio signal played by the loudspeaker collected by the microphone, and v represents external interference noise collected by the microphone, and then the two paths of signal sequence are subjected to high-pass filtering to filter the influence of the direct current signal.
(2) Computing a normalized autocorrelation sequence r of a source audio signal xx (l) And calculating a normalized cross-correlation sequence r between the feedback audio signal and the source audio signal yx (l) It can be calculated as follows:
where l is the length of the signal, μ v ,μ x Respectively representing the statistical mean of the ambient noise and the source audio signal, and having μ assuming that the ambient noise and the source audio signal are signals whose statistical mean is 0 v ＝0,μ x =0, the cross-correlation of two independent incoherent signals satisfies r vx ≈μ v μ x =0, therefore, the correlation mainly includes the related information of two signals, and has a suppressing effect on irrelevant information.
(3) For a system, the cross-correlation r of the output and input is based on the minimum mean square error criterion of the optimum coefficients yx (l) Can be auto-correlated by the input signal r xx (l) Convolution with the system transfer function h (l) yields the followingThe relationship is as follows:
as can be seen from the above equation, the time-domain transfer function of the system can be calculated according to the autocorrelation and the cross-correlation, and the filter coefficients of the time-domain transfer function can be estimated as:
wherein, h' represents a coefficient vector,
representing an N x N toeplitz matrix,
is an element of gamma yx (l) N × 1 cross-correlation vector of (a).
It can be found from the calculation formula of the time domain transfer function of the system that the time domain transfer function contains the cross-correlation information. The cross correlation mainly comprises the related information of two paths of signals and has a suppression effect on the unrelated information, so that the time domain transfer function can effectively suppress the interference of external noise as the same frequency domain transfer function, and the representation of the time domain transfer function is also the information of the acoustic system, and has no specific requirements on an audio source.
(4) The wearing state is distinguished by means of the Euclidean distance between the time domain transfer function and the target transfer function. Wherein the target transfer function h d I.e. the transfer function corresponding to the case of a well coupled earpiece and ear canal. The target transfer function may be obtained according to the following manner: a target transfer function can be obtained through statistics according to a large number of corresponding transfer functions when different people are tightly worn; or in the case of a good sealing of the earpiece with the ear canal simulator, the resulting transfer function is taken as the target transfer function. According to
Calculating a time domain transfer function h' and a target transfer function h d And at the Euclidean distance d of each signal sequence sampling point, if the Euclidean distance d is smaller than a distance threshold TH, the wearing state of the earphone at the moment is considered to be tightly fitted, and the output mark is 1, otherwise, the wearing state of the earphone at the moment is considered to be not tightly fitted, and the output mark is 0. It is easy to understand that the lamination state can be divided into four or more levels based on the euclidean distance, active noise reduction filters which are in one-to-one correspondence with each level and have preset amplitude-frequency response are respectively arranged, and the selection is carried out in a self-adaptive manner according to the level of the currently judged lamination state, so that a finer self-adaptive adjustment effect is achieved.
The wearing fit state of the earphone can be effectively detected by the steps (1) to (4), and a proper active noise reduction filter is selected based on the detection result.
The principle of active noise reduction is that a signal is generated after passing through an active noise reduction filter, and the signal has opposite phase and same amplitude with an external interference noise signal leaked into an auditory canal, so that the external interference noise in the auditory canal is offset, and the noise reduction effect is achieved.
The embodiment of the application is based on the principle that when the active noise reduction filter is selected according to the fitting state of the earphone and the ear canal of the human ear: if the fit is less tight, the sealing performance between the earphone and the auditory canal of the human ear is poorer, the external interference noise leaked into the auditory canal is more, the amplitude is larger, and at the moment, the active noise reduction filter capable of generating reverse signals with larger amplitude needs to be selected to offset the external interference noise. On the contrary, if the fitting is tighter, the external interference noise entering the ear canal is relatively less, and at this time, the active noise reduction filter capable of generating a reverse signal with a smaller amplitude is selected to cancel the external interference noise.
As shown in fig. 3, a schematic diagram of a selection process of an active noise reduction filter according to an embodiment of the present application is provided. Specifically, fig. 3 shows the selection conditions of the active noise reduction filters corresponding to the four attachment states, and if the attachment state is werstatus 1, it indicates that the attachment between the earphone and the ear canal of the human ear is tight enough, and the external interference noise leaked into the ear canal is very little, and at this time, the active noise reduction filter with a small amplitude-frequency response is selected; if the attaching state is WeartStatus 2, the attaching of the earphone and the ear canal of the human ear is tight, but the external interference noise leaked into the ear canal is slightly increased, and an active noise reduction filter with slightly small amplitude-frequency response can be selected; if the attaching state is WeartStatus 3, which indicates that the external interference noise leaked into the auditory canal is more, an active noise reduction filter with slightly larger amplitude-frequency response can be selected; if the attaching state is WeartStatus 4, which indicates that the external interference noise leaked into the ear canal is very much, an active noise reduction filter with large amplitude-frequency response can be selected.
In another embodiment of the present application, adaptively selecting a corresponding active noise reduction filter according to a fitting state of an earphone to an ear canal of a human ear includes: acquiring a preset comparison table, wherein the preset comparison table stores the corresponding relation between the attachment state and the amplitude-frequency response of the active noise reduction filter; and selecting an active noise reduction filter with amplitude-frequency response corresponding to the joint state from a preset comparison table according to the joint state of the earphone and the ear canal of the human ear.
The active noise reduction filter can be set in advance in different attaching states, namely, the corresponding relation between the different attaching states and the amplitude-frequency response of the different active noise reduction filters can be established in advance, and then the corresponding relation is stored in a preset comparison table so as to facilitate subsequent query and selection.
The selection mode of the active noise reduction filter may adopt a mode of self-adaptively switching according to the detected different attaching states, for example, when the detected attaching state is werstatus 1, the active noise reduction filter A1 with amplitude-frequency response corresponding to werstatus 1 may be searched from the preset comparison table, so as to perform active noise reduction by using the active noise reduction filter A1. If the attachment state is detected to be changed into the werstatus 2 subsequently, the active noise reduction filter A2 with the amplitude-frequency response corresponding to the werstatus 2 can be inquired from the preset comparison table, and the current active noise reduction filter is switched from the A1 to the A2, so that the purpose of adaptively matching the corresponding active noise reduction filter according to the attachment state is achieved, a user can feel a good noise reduction effect under different earphone wearing conditions, and the use experience of the user is improved.
It should be noted that, in the embodiment of the present application, the detection frequency of the fitting state between the earphone and the ear canal of the human ear may be detected in real time, or may be detected at intervals, and how to set the detection frequency is specifically set, and a person skilled in the art may flexibly set the detection frequency according to actual situations, and is not limited specifically herein.
In one embodiment of the present application, the active noise reduction filter includes a feedback noise reduction filter and a feedforward noise reduction filter.
The active noise reduction filter of the embodiment of the application may include a feedback noise reduction filter and a feedforward noise reduction filter, and therefore, the feedforward noise reduction filter and the feedback noise reduction filter corresponding to different attachment states may be stored in the preset comparison table in advance.
In an actual application scene, if the earphone is only provided with the feedback noise reduction filter, after the bonding state is detected, the feedback noise reduction filter corresponding to the bonding state is directly started; if the earphone is provided with the feedforward noise reduction filter and the feedback noise reduction filter at the same time, the feedforward noise reduction filter and the feedback noise reduction filter corresponding to the bonding state can be started at the same time after the bonding state is detected. That is to say, the active noise reduction filter to be turned on may be selected according to the actual setting condition of the active noise reduction filter by the headset.
In one embodiment of the present application, adaptively selecting a corresponding active noise reduction filter according to a fitting state of an earphone and an ear canal of a human ear includes: and adaptively setting parameters of the active noise reduction filter.
The preset parameters of the active noise reduction filter corresponding to different attachment states can be obtained through empirical measurement, and the following measurement modes are taken as examples:
a group of testees is selected, and for each tester, the optimal feedback noise reduction filter and the optimal feedforward noise reduction filter in four fitting states are tested. And after all tests are finished, taking the average value of the parameters of the optimal feedforward noise reduction filter measured by a plurality of testees as the feedforward noise reduction filter in the bonding state for each bonding state. Similarly, the average value of the parameters of the optimal feedback noise reduction filter measured by a plurality of testees is used as the feedback noise reduction filter in the fitting state.
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, the open loop response is multiplied by two parts: a feedback noise reduction filter response and a speaker-feedback microphone frequency response, such that 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 the wearing is good can be used as the unique open loop response function L.
In the case where the human subject and the fitting state are determined, the measurement calculation process of the feedback noise reduction filter is as follows: measuring the frequency Response of the loudspeaker-feedback microphone in different bonding states as a divisor, taking the unique open loop Response as a dividend, obtaining the frequency Response of the feedback noise reduction filter, and according to the frequency Response of the feedback noise reduction filter, performing frequency domain-time domain inverse Fourier transform processing to obtain a feedback noise reduction filter in the form of FIR (Finite Impulse Response filter), or directly obtaining the feedback noise reduction filter in the form of IIR (Infinite Impulse Response filter) according to the frequency Response, wherein any one of FIR or IIR can be selected in a practical application scene.
The measurement and calculation of the feedforward noise reduction filter is based on the following principle: assuming that the transfer function of the noise conducted into the ear at the feedforward microphone is P, the feedforward noise reduction filter is the transfer function P of the noise conducted into the ear divided by the frequency response Gf of the speaker into the ear.
In the case of a human subject and a fit state determination, the measurement calculation process of the feedforward noise reduction filter is as follows: the method comprises the steps of generating noise outside the earphone, measuring a transfer function P from the noise at the feedforward microphone to the noise in the ear, taking the transfer function P as a dividend and a frequency response Gf from a loudspeaker to the ear at the moment as a divisor, performing division calculation to obtain a frequency response of a feedforward noise reduction filter, performing frequency domain-time domain inverse Fourier transform processing to obtain the feedforward noise reduction filter in an FIR form after obtaining the frequency response, and directly solving the feedforward noise reduction filter in an IIR form according to the frequency response.
Due to physical characteristics, amplitude-frequency responses of the feedback noise reduction filter and the feedforward noise reduction filter have the characteristics that the more external interference noise is leaked into an ear canal, and the higher the amplitude-frequency response of low-frequency amplitude is.
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 transfer function of the speaker and the feedback microphone, when the external interference noise leaked into the ear canal becomes more, the low-frequency amplitude in the transfer function between the speaker and the feedback microphone is attenuated more, and correspondingly, the amplitude of the feedback noise reduction filter is increased, that is, the amplitude-frequency response of the selected feedback noise reduction filter at the low frequency band is larger. When the external interference noise leaked into the ear canal becomes less, the low-frequency amplitude attenuation of the transfer function between the loudspeaker and the feedback microphone is small, and correspondingly, the amplitude-frequency response of the selected feedback noise reduction filter in the low frequency band is small.
For the feedforward noise reduction filter, when external interference noise leaked into an ear canal becomes more, the frequency response Gf from a loudspeaker to the ear is attenuated more at low frequency amplitude, and the amplitude of the transfer function P from noise at a feedforward microphone to the in-ear noise becomes larger at the full frequency band, so that the amplitude-frequency response P/Gf of the feedforward noise reduction filter becomes larger. When the external interference noise leaked into the ear canal is reduced, the frequency response Gf from the loudspeaker to the ear is attenuated little at low frequency amplitude, and the amplitude of the transfer function P from the noise at the feedforward microphone to the noise in the ear is reduced at the full frequency band, so that the amplitude-frequency response P/Gf of the feedforward noise reduction filter is reduced.
As shown in fig. 4, a block diagram of the active noise reduction process of the earphone according to an embodiment of the present application is provided, which mainly includes the following parts:
(1) Audio signal acquisition: acquiring a source audio signal input to a loudspeaker and a feedback audio signal collected by a microphone;
(2) Detection of a bonding state: the bonding state is detected by using a source audio signal input to the speaker and a feedback audio signal collected by the microphone. Firstly, transforming the obtained source audio signal and feedback audio signal to a frequency domain for processing; then, a self-power spectrum of the source audio signal and a cross-power spectrum of the feedback audio signal and the source audio signal are calculated by using a periodogram method or other spectrum estimation methods, such as a parameter spectrum estimation method. And then, calculating a frequency domain transfer function by using the self-power spectrum of the source audio signal and the cross-power spectrum of the feedback audio signal and the source audio signal.
(3) Outputting a bonding state: and determining different fit states according to the ratio of the average values of the low-frequency amplitude and the intermediate-frequency amplitude in the frequency domain transfer function.
(4) Selection of active noise reduction filter: and automatically matching the corresponding active noise reduction filter according to the detected fitting state. Under the same background noise environment, the closer the fit is, the smaller the amplitude of the reverse signal that can be generated by the selected active noise reduction filter is, and vice versa.
Through the active noise reduction process of the earphone, the purpose of adaptively matching the corresponding active noise reduction filter according to the fitting state is achieved, so that a user can feel a good noise reduction effect under different earphone wearing conditions, and the use experience of the user is improved.
The method belongs to the same technical concept as the active noise reduction method of the earphone, and the embodiment of the application also provides an active noise reduction device of the earphone. Fig. 5 is a schematic structural diagram of an active noise reduction device of a headphone according to an embodiment of the present application, and referring to fig. 5, the headphone includes a speaker and a microphone for collecting an audio signal played by the speaker, and the active noise reduction device 500 of the headphone includes: an audio signal acquisition unit 510, a transfer function determination unit 520, a fit state determination unit 530, and an active noise reduction unit 540. Wherein the content of the first and second substances,
an audio signal acquiring unit 510, configured to acquire a source audio signal input to a speaker and a feedback audio signal acquired by a microphone;
a transfer function determining unit 520 for determining a transfer function from the source audio signal and the feedback audio signal;
a fitting state determining unit 530 for determining a fitting state of the earphone and the ear canal of the human ear according to the transfer function;
and the active noise reduction unit 540 is configured to adaptively select a corresponding active noise reduction filter according to a fit state of the earphone and the ear canal of the human ear, so as to actively reduce noise through the active noise reduction filter.
In an embodiment of the present application, the transfer function determining unit 520 is specifically configured to: calculating the self-power spectrum of the source audio signal by using a preset power spectrum estimation method, and feeding back the cross-power spectrum of the audio signal and the source audio signal; respectively smoothing the self-power spectrum and the cross-power spectrum in a preset time period to obtain an average self-power spectrum and an average cross-power spectrum; and determining a transfer function according to the ratio of the average cross-power spectrum to the average self-power spectrum.
In an embodiment of the present application, the attachment state determining unit 530 is specifically configured to: determining an average value of low frequency amplitude and an average value of medium frequency amplitude in the transfer function; and detecting the fitting state of the earphone and the ear canal of the human ear according to the ratio of the average value of the low-frequency amplitude to the average value of the medium-frequency amplitude.
For example, the ratio of the average value of the low frequency amplitude to the average value of the medium frequency amplitude is compared with a preset threshold; based on the result of the comparison, the fitting state of the earphone with the ear canal of the human ear is determined.
In an embodiment of the present application, the active noise reduction unit 540 is specifically configured to: if the fit state of the earphone and the ear canal of the human ear is a tight state, an active noise reduction filter with lower amplitude-frequency response is selected in a self-adaptive manner; and if the fit state of the earphone and the ear canal of the human ear is not a tight state, the active noise reduction filter with higher amplitude-frequency response is selected in a self-adaptive mode.
In another embodiment of the present application, the active noise reduction unit 540 is specifically configured to: acquiring a preset comparison table, wherein the preset comparison table stores the corresponding relation between the attachment state and the amplitude-frequency response of the active noise reduction filter; and selecting an active noise reduction filter with amplitude-frequency response corresponding to the fitting state in a preset comparison table according to the fitting state of the earphone and the ear canal of the human ear.
In one embodiment of the present application, the active noise reduction filter includes a feedback noise reduction filter and a feedforward noise reduction filter.
In an embodiment of the present application, the active noise reduction unit 540 is specifically configured to: and adaptively setting parameters of the active noise reduction filter.
In one embodiment of the present application, wherein the transfer function is a time-domain transfer function.
In an embodiment of the present application, the transfer function determining unit 520 is specifically configured to: high-pass filtering the source audio signal and the feedback audio signal respectively; obtaining a normalized autocorrelation sequence of the source audio signal and a normalized cross-correlation 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 time domain transfer function according to the minimum mean square error criterion and by utilizing the normalized autocorrelation sequence and the normalized cross-correlation sequence.
In an embodiment of the present application, the attachment state determining unit 530 is specifically configured to: acquiring Euclidean distance between a time domain transfer function and a predetermined target transfer function at each signal sequence sampling point; and determining the fitting state of the earphone and the ear canal of the human ear based on the Euclidean distance.
It should be noted that:
fig. 6 illustrates a schematic structural diagram of an active noise reduction headphone. Referring to fig. 6, in a hardware level, the active noise reduction earphone includes a speaker, a microphone for collecting sound signals in an ear canal, a processor, a memory for storing computer executable instructions, and optionally an interface module, a communication module, and the like. The Memory may include a Memory, such as a Random-Access Memory (RAM), and may also include a non-volatile Memory, such as at least one disk Memory. Of course, the active noise reduction headphones may also include hardware needed for other services.
The processor, the speaker, the microphone, and the memory may be connected to each other via an internal bus, which may be an ISA (Industry Standard Architecture) bus, a PCI (Peripheral Component Interconnect) bus, an EISA (Extended Industry Standard Architecture) bus, or the like. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one double-headed arrow is shown in FIG. 6, but this does not indicate only one bus or one type of bus.
A memory for storing computer executable instructions. The memory provides computer executable instructions to the processor through the internal bus.
A processor executing computer executable instructions stored in the memory and specifically configured to perform the following operations:
acquiring a source audio signal input to a loudspeaker and a feedback audio signal collected by a microphone;
determining a transfer function from the source audio signal and the feedback audio signal;
determining the fitting state of the earphone and the ear canal of the human ear according to the transfer function;
and according to the fitting state of the earphone and the ear canal of the human ear, a corresponding active noise reduction filter is selected in a self-adaptive manner so as to carry out active noise reduction through the active noise reduction filter.
The functions performed by the active noise reduction device of the earphone according to the embodiment shown in fig. 5 of the present application may be implemented in or by a processor. The processor may be an integrated circuit chip having signal processing capabilities. In the implementation process, the steps of the active noise reduction method for a headphone disclosed in the embodiment shown in fig. 1 of the present application may be implemented by an integrated logic circuit of hardware in a processor or instructions in the form of software. The Processor may be a general-purpose Processor, including a Central Processing Unit (CPU), a Network Processor (NP), and the like; but also Digital Signal Processors (DSPs), application Specific Integrated Circuits (ASICs), field Programmable Gate Arrays (FPGAs) or other Programmable logic devices, discrete Gate or transistor logic devices, discrete hardware components. The various methods, steps, and logic blocks disclosed in the embodiments of the present application may be implemented or performed. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. The steps of the method disclosed in connection with the embodiments of the present application may be directly implemented by a hardware decoding processor, or implemented by a combination of hardware and software modules in the decoding processor. The software module may be located in ram, flash memory, rom, prom, or eprom, registers, etc. storage media as is well known in the art. The storage medium is located in a memory, and a processor reads information in the memory and combines hardware thereof to complete the steps of the method.
An embodiment of the present application further provides a computer-readable storage medium, which stores one or more programs, which when executed by a processor, implement the foregoing active noise reduction method for a headset, and is specifically configured to perform:
acquiring a source audio signal input to a loudspeaker and a feedback audio signal collected by a microphone;
determining a transfer function from the source audio signal and the feedback audio signal;
determining the fitting state of the earphone and the ear canal of the human ear according to the transfer function;
and according to the fitting state of the earphone and the ear canal of the human ear, a corresponding active noise reduction filter is selected in a self-adaptive manner so as to carry out active noise reduction through the active noise reduction filter.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied 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 code.
The present application is described in terms of flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
In a typical configuration, a computing device includes one or more processors (CPUs), input/output interfaces, network interfaces, and memory.
The memory may include forms of volatile memory in a computer readable medium, random Access Memory (RAM) and/or non-volatile memory, such as Read Only Memory (ROM) or flash memory (flash RAM). Memory is an example of a computer-readable medium.
Computer-readable media, including both non-transitory and non-transitory, removable and non-removable media, may implement information storage by any method or technology. The information may be computer readable instructions, data structures, modules of a program, 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 disc read only memory (CD-ROM), digital Versatile Disks (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium, which can be used to store information that can be accessed by a computing device. As defined herein, a computer readable medium does not include a transitory computer readable medium such as a modulated data signal and a carrier wave.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional identical elements in the process, method, article, or apparatus comprising the element.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) characterized by computer-usable program code.
The above are merely examples of the present application and are not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.
Claims (14)
1. An active noise reduction method for an earphone, the earphone including a speaker and a microphone for collecting sound signals in an ear canal, the method comprising:
acquiring a source audio signal input to the loudspeaker and a feedback audio signal collected by the microphone;
determining a transfer function from the source audio signal and the feedback audio signal;
determining the fitting state of the earphone and the ear canal of the human ear according to the transfer function;
and according to the fitting state of the earphone and the ear canal of the human ear, adaptively selecting a corresponding active noise reduction filter so as to actively reduce noise through the active noise reduction filter.
2. The method of claim 1, wherein the transfer function is a frequency domain transfer function.
3. The method of claim 2, wherein determining a transfer function from the source audio signal and the feedback audio signal comprises:
calculating the self-power spectrum of the source audio signal and the cross-power spectrum of the feedback audio signal and the source audio signal by using a preset power spectrum estimation method;
respectively smoothing the self-power spectrum and the cross-power spectrum in a preset time period to obtain an average self-power spectrum and an average cross-power spectrum;
and determining the transfer function according to the ratio of the average cross-power spectrum to the average self-power spectrum.
4. The method of claim 2, wherein determining the fit state of the earpiece to the ear canal of the human ear from the transfer function comprises:
determining an average of low frequency amplitudes and an average of medium frequency amplitudes in the transfer function;
and detecting the fitting state of the earphone and the ear canal of the human ear according to the ratio of the average value of the low-frequency amplitude to the average value of the medium-frequency amplitude.
5. The method of claim 4, wherein the detecting the fitting state of the earphone to the ear canal of the human ear according to the ratio of the average value of the low frequency amplitude to the average value of the medium 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;
and determining the fitting state of the earphone and the ear canal of the human ear based on the comparison result.
6. The method of claim 2, wherein adaptively selecting the corresponding active noise reduction filter according to the fit state of the earphone to the ear canal of the human ear comprises:
if the fitting state of the earphone and the ear canal of the human ear is a tight state, an active noise reduction filter with lower amplitude-frequency response is selected in a self-adaptive manner;
and if the fitting state of the earphone and the ear canal of the human ear is not tight, the active noise reduction filter with higher amplitude-frequency response is selected in a self-adaptive manner.
7. The method of claim 2, wherein the adaptively selecting the corresponding active noise reduction filter according to the fitting state of the earphone to the ear canal of the human ear comprises:
acquiring a preset comparison table, wherein the preset comparison table stores the corresponding relation between the attaching state and the amplitude-frequency response of the active noise reduction filter;
and selecting an active noise reduction filter with amplitude-frequency response corresponding to the fitting state in the preset comparison table according to the fitting state of the earphone and the ear canal of the human ear.
8. The method of claim 1, wherein the active noise reduction filter comprises a feedback noise reduction filter and a feedforward noise reduction filter.
9. The method of claim 1 or 8, wherein adaptively selecting a corresponding active noise reduction filter according to a fit state of the earphone with an ear canal of a human ear comprises:
and adaptively setting parameters of the active noise reduction filter.
10. The method of claim 1, wherein the transfer function is a time-domain transfer function.
11. The method of claim 10, wherein the determining a transfer function from the source audio signal and the feedback audio signal comprises:
high-pass filtering the source audio signal and the feedback audio signal, respectively;
obtaining a normalized autocorrelation sequence of the source audio signal and a normalized cross-correlation 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 the time domain transfer function according to a minimum mean square error criterion and by utilizing the normalized autocorrelation sequence and the normalized cross-correlation sequence.
12. The method of claim 11, wherein said determining a fit state of the earpiece to the ear canal of the human ear from the transfer function comprises:
acquiring Euclidean distance between the time domain transfer function and a predetermined target transfer function at each signal sequence sampling point;
and determining the fitting state of the earphone and the ear canal of the human ear based on the Euclidean distance.
13. An active noise reduction device for a headphone, the headphone comprising a speaker and a microphone for collecting audio signals played by the speaker, the device comprising:
the audio signal acquisition unit is used for acquiring a source audio signal input to the loudspeaker and a feedback audio signal acquired by the microphone;
a transfer function determination unit for determining a transfer function from the source audio signal and the feedback audio signal;
the fit state determining unit is used for determining the fit state of the earphone and the ear canal of the human ear according to the transfer function;
and the active noise reduction unit is used for adaptively selecting a corresponding active noise reduction filter according to the fitting state of the earphone and the ear canal of the human ear so as to actively reduce noise through the active noise reduction filter.
14. An active noise reducing headphone, comprising: a speaker, a microphone for collecting sound signals within the ear canal, a processor, a memory storing computer executable instructions,
the computer executable instructions, when executed by the processor, implement the active noise reduction method for headphones of any of claims 1-12.
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