CN111800694A - Filter design method and device of active noise reduction earphone and test equipment - Google Patents
Filter design method and device of active noise reduction earphone and test equipment Download PDFInfo
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- CN111800694A CN111800694A CN202010614861.4A CN202010614861A CN111800694A CN 111800694 A CN111800694 A CN 111800694A CN 202010614861 A CN202010614861 A CN 202010614861A CN 111800694 A CN111800694 A CN 111800694A
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- H04R1/00—Details of transducers, loudspeakers or microphones
- H04R1/10—Earpieces; Attachments therefor ; Earphones; Monophonic headphones
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- 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
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- 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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Abstract
The application is suitable for the technical field of noise reduction earphones, and provides a filter design method and device of an active noise reduction earphone and test equipment. According to the method, a feedback filter is designed in advance, and then according to a frequency response curve of the feedback filter, a transfer function from external noise to a standard microphone in an ear canal, a transfer function from a loudspeaker to the standard microphone in the ear canal, a transfer function from the external noise to a feedforward microphone, a transfer function from the external noise to the feedback microphone and a transfer function from the loudspeaker to the feedback microphone, the influence on an ideal frequency response curve of the feedforward filter when the feedback filter is opened for noise reduction is analyzed, the ideal frequency response curve of the feedforward filter is corrected, and therefore the feedforward filter with a mixed noise reduction effect meeting the expectation can be designed according to the corrected ideal frequency response curve of the feedforward filter.
Description
Technical Field
The application belongs to the technical field of Noise reduction earphones (Noise-Cancellation earphones), and particularly relates to a filter design method and device of an active Noise reduction earphone and test equipment.
Background
The noise reduction headphone refers to a headphone capable of reducing noise in the external environment. The noise reduction earphone comprises an active noise reduction earphone and a passive noise reduction earphone. The active noise reduction is to generate sound waves with the same amplitude and reverse phase with the noise in the external environment through a loudspeaker to offset the noise in the external environment, and the reduction has obvious effect on the noise in the middle and low frequency bands. Passive noise reduction is to block noise in the external environment by sound insulation parts such as earmuffs and earplugs, and generally only works on high-frequency noise above 1 kHz.
Currently, in order to achieve a good noise reduction effect, an active noise reduction headphone usually uses a feedforward filter and a feedback filter to achieve hybrid noise reduction (hybrid noise reduction). However, in designing the feedforward filter and the feedback filter, there are problems that the effect of the hybrid noise reduction is not a linear superposition of the noise reduction effect of the feedforward filter and the noise reduction effect of the feedback filter, and the noise reduction effect in some frequency bands is greatly different from the expected one.
Disclosure of Invention
In view of this, embodiments of the present application provide a method, an apparatus, and a testing device for designing a filter of an active noise reduction earphone, so as to solve the problems that in the process of designing a feedforward filter and a feedback filter in the prior art, the effect of mixed noise reduction is not linear superposition of the noise reduction effect of the feedforward filter and the noise reduction effect of the feedback filter, and the noise reduction effect in some frequency bands has a large difference from an expected noise reduction effect.
A first aspect of an embodiment of the present application provides a method for designing a filter of an active noise reduction headphone, including:
modifying the ideal frequency response curve of the feedforward filter according to the frequency response curve of the feedback filter, the transfer function of the external noise to a standard microphone in the ear canal, the transfer function of the loudspeaker to the standard microphone in the ear canal, the transfer function of the external noise to the feedforward microphone, the transfer function of the external noise to the feedback microphone and the transfer function of the loudspeaker to the feedback microphone;
and designing the feedforward filter according to the corrected ideal frequency response curve of the feedforward filter.
A second aspect of the embodiments of the present application provides a filter design apparatus for an active noise reduction earphone, including:
the correction module is used for correcting the ideal frequency response curve of the feedforward filter according to the frequency response curve of the feedback filter, the transfer function of external noise to a standard microphone in an ear canal, the transfer function of a loudspeaker to the standard microphone in the ear canal, the transfer function of the external noise to the feedback microphone and the transfer function of the loudspeaker to the feedback microphone;
and the design module is used for designing the feedforward filter according to the corrected ideal frequency response curve of the feedforward filter.
A third aspect of embodiments of the present application provides a testing device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, the processor implementing the steps of the filter design method for an active noise reduction earphone according to the first aspect of embodiments of the present application when executing the computer program.
A fourth aspect of embodiments of the present application provides a computer-readable storage medium storing a computer program, which when executed by a processor implements the steps of the filter design method for an active noise reduction headphone according to the first aspect of embodiments of the present application.
According to the method and the device, the ideal frequency response curve of the feedforward filter is modified according to the frequency response curve of the feedback filter, the transfer function of external noise to a standard microphone in an ear canal, the transfer function of a loudspeaker to a standard microphone in the ear canal, the transfer function of external noise to the feedforward microphone, the transfer function of external noise to the feedback microphone and the transfer function of the loudspeaker to the feedback microphone, the feedforward filter is designed according to the modified ideal frequency response curve of the feedforward filter, the feedback filter can be designed independently, then the influence on the ideal frequency response curve of the feedforward filter when the feedback filter is opened for noise reduction is analyzed according to the frequency response curve of the feedback filter and the noise transfer function related to an earphone, the modified ideal frequency response curve of the feedforward filter is obtained, and therefore the mixed noise reduction effect is matched according to the modified ideal frequency response curve of the feedforward filter A desired feedforward filter.
It is understood that the beneficial effects of the second to fourth aspects can be seen from the description of the first aspect, and are not described herein again.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
Fig. 1 is a schematic structural diagram of an active noise reduction earphone provided in an embodiment of the present application;
fig. 2 is a schematic structural diagram of an earphone testing system provided in an embodiment of the present application;
fig. 3 is a first flowchart illustrating a filter design method for an active noise reduction headphone according to an embodiment of the present application;
fig. 4 is a second flowchart illustrating a filter design method for an active noise reduction headphone according to an embodiment of the present application;
FIG. 5 is a schematic diagram of an ideal amplitude-frequency characteristic curve of a feedforward filter and an ideal amplitude-frequency characteristic curve of a modified feedforward filter according to an embodiment of the present application;
FIG. 6 is a diagram illustrating an ideal phase-frequency characteristic of a feedforward filter and an ideal phase-frequency characteristic of a modified feedforward filter according to an embodiment of the present application;
fig. 7 is a third flowchart illustrating a filter design method for an active noise reduction headphone according to an embodiment of the present application;
fig. 8 is a fourth flowchart illustrating a filter design method for an active noise reduction headphone according to an embodiment of the present application;
FIG. 9 is a diagram illustrating a linear superposition curve of the noise reduction effect of the feedforward filter and the noise reduction effect of the feedback filter and a modified mixed noise reduction effect curve according to an embodiment of the present application;
FIG. 10 is a schematic diagram of an ideal amplitude-frequency characteristic of a feedforward filter after adjusting an acoustic resistance material covering a leak hole of a front acoustic cavity and an ideal amplitude-frequency characteristic of a feedforward filter after modification according to an embodiment of the present application;
FIG. 11 is a schematic diagram of an ideal phase-frequency characteristic of a feedforward filter after adjusting an acoustic resistance material covering a leak hole of a front acoustic cavity and an ideal phase-frequency characteristic of a modified feedforward filter according to an embodiment of the present application;
fig. 12 is a schematic structural diagram of a filter design apparatus according to an embodiment of the present application;
fig. 13 is a schematic structural diagram of a test apparatus provided in an embodiment of the present application.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular system structures, techniques, etc. in order to provide a thorough understanding of the embodiments of the present application. It will be apparent, however, to one skilled in the art that the present application may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary detail.
It will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Furthermore, in the description of the present application and the appended claims, the terms "first," "second," "third," and the like are used for distinguishing between descriptions and not necessarily for describing or implying relative importance.
Reference throughout this specification to "one embodiment" or "some embodiments," or the like, means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the present application. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," or the like, in various places throughout this specification are not necessarily all referring to the same embodiment, but rather "one or more but not all embodiments" unless specifically stated otherwise. The terms "comprising," "including," "having," and variations thereof mean "including, but not limited to," unless expressly specified otherwise.
The embodiment of the application provides a filter design method of an active noise reduction earphone, which is used for designing a feedback filter and a feedforward filter which enable the mixed noise reduction effect of the active noise reduction earphone to meet the expectation. The filter design method can be applied to test equipment for designing and calculating performance parameters of each component in the active noise reduction earphone, and can be executed by a processor of the test equipment when a computer program is run. The testing device may be a computing device with data processing and computing functions, such as a tablet computer, a notebook computer, a desktop computer, a Personal Computer (PC), and the like, and the specific type of the testing device is not limited in any way in the embodiments of the present application.
In application, an active noise reduction earphone generally includes a feedforward microphone, a feedforward filter, one or two speakers, a feedback microphone, and a feedback filter. When the active noise reduction earphone is a Bluetooth earphone, the active noise reduction earphone can further comprise a rechargeable battery and a wireless communication module; when the active noise reduction earphone is a wired earphone, the active noise reduction earphone can further comprise an earphone wire and an earphone interface, and the specific type of the active noise reduction earphone is not limited in any way in the embodiment of the application.
As shown in fig. 1, a schematic diagram of an active noise reduction earphone is exemplarily shown; the active noise reduction earphone 10 includes a feedforward microphone 1, a feedforward filter 2, a loudspeaker 3, a feedback microphone 4 and a feedback filter 5, solid arrows between the feedforward microphone 1, the feedforward filter 2, the loudspeaker 3, the feedback microphone 4 and the feedback filter 5 indicate transmission directions of analog or digital signals, dotted arrows between external noise 6 and the feedforward microphone 1, the feedback microphone 4 and the standard microphone 7 indicate transmission directions of noise, and dotted arrows between the loudspeaker 3 and the feedback microphone 4 and the standard microphone 7 indicate transmission directions of sound signals.
In the application, in the process of designing the filter of the active noise reduction earphone, the earphone test system is required to test the performance of the active noise reduction earphone. The earphone testing system generally comprises a sound box, a simulation human head (the simulation human head comprises one or two simulation ears), an audio analyzer, testing equipment and the like. The sound box is used for emitting noise to simulate the noise in the external environment. The earplug of the active noise reduction earphone is inserted into the ear canal of the artificial ear so as to simulate the scene that the earphone of the active noise reduction earphone is inserted into the ear canal of the human ear. The audio analyzer is used for analyzing the noise output by the sound box and the sound signals output by the active noise reduction earphone and the simulation ear respectively so as to obtain the frequency, the amplitude, the phase, the signal-to-noise ratio and other parameters of the noise and the sound signals. The test equipment is used for analyzing and calculating the parameters to obtain a transfer function of external noise (namely, noise output by the sound box) to a standard microphone in an ear canal, a transfer function of a loudspeaker to the standard microphone in the ear canal, a transfer function of the external noise to a feedforward microphone, a transfer function of the external noise to a feedback microphone, a transfer function of the loudspeaker to the feedback microphone and other noise transfer functions related to the earphone, so as to realize the filter design method.
In use, the ear canal may be that of a simulated ear, or that of a human ear. The artificial ear may be replaced by a human ear to obtain a noise transfer function related to the earphone, such as a transfer function of external noise to a standard microphone in the ear canal, a transfer function of a speaker to a standard microphone in the ear canal, a transfer function of external noise to a feedforward microphone, a transfer function of external noise to a feedback microphone, a transfer function of a speaker to a feedback microphone, and the like, when the active noise reduction earphone is worn by the human ear. The artificial ear is replaced by the human ear, so that the design of the personalized active noise reduction earphone matched with the human ear can be realized, and the personalized customization requirements of users can be met.
As shown in fig. 2, a schematic diagram of a testing system of a headset is exemplarily shown; the earphone testing system includes a sound box 20, a simulated human head 30, an audio analyzer and a testing device (not shown in the figure), and the simulated human head 30 includes a simulated ear 31.
As shown in fig. 3, a method for designing a filter of an active noise reduction earphone according to an embodiment of the present application includes:
step S301, an ideal frequency response curve of the feedforward filter is corrected according to a frequency response curve of the feedback filter, a transfer function of external noise to a standard microphone in an ear canal, a transfer function of a loudspeaker to the standard microphone in the ear canal, a transfer function of the external noise to the feedforward microphone, a transfer function of the external noise to the feedback microphone and a transfer function of the loudspeaker to the feedback microphone.
In application, the feedback filter is designed in advance before step S301 is executed, and the frequency response curve of the feedback filter, the transfer function of the external noise to the standard microphone in the ear canal, the transfer function of the speaker to the standard microphone in the ear canal, the transfer function of the external noise to the feedback microphone, and the transfer function of the speaker to the feedback microphone are all known parameters measured in advance by the earphone testing system. Since the feedback filter has a certain influence on the ideal frequency response curve of the feedforward filter when the feedback filter and the feedforward filter are simultaneously turned on, the ideal frequency response curve of the feedforward filter needs to be corrected by taking the influence of the feedback filter on the ideal frequency response curve of the feedforward filter into consideration when the feedforward filter is designed.
In one embodiment, the modified feedforward filter has an ideal frequency response curve expressed by:
Hf_target_new＝(Tae/Tde–Hb*Nb*Tab)/(Taf*(1-Hb*Nb*Tdb))；
Nb＝1/(1+Tdb*Hb)；
where Hf _ target _ new represents an ideal frequency response curve of the feedforward filter after correction, Hb represents a frequency response curve of the feedback filter, Tae represents a transfer function of external noise to a standard microphone in the ear canal, Tde represents a transfer function of a speaker to a standard microphone in the ear canal, Taf represents a transfer function of external noise to the feedforward microphone, Tab represents a transfer function of external noise to the feedback microphone, Tdb represents a transfer function of a speaker to the feedback microphone, and Nb represents a noise reduction rate at the feedback microphone when noise reduction alone is performed by the feedback filter.
In application, the derivation of the expression for the ideal frequency response curve of the modified feedforward filter is as follows:
1) let the total residual noise at a standard microphone in the ear canal be 0, which is expressed as:
tae-eb1 Hb Tde-Taf Hf _ target _ new Tde 0; (expression one)
2) The expression of the ideal noise at the feedback microphone when performing mixed noise reduction by the feedback filter and the feedforward filter is:
eb1 ═ Nb (Tab-Tdb ═ Hf _ target _ new ═ Taf); (expression two)
3) Secondly, the expression is put into the expression I to obtain an expression of the corrected ideal frequency response curve of the feedforward filter;
where eb1 represents the ideal noise at the feedback microphone when noise reduction is performed by mixing the feedback filter and the feedforward filter.
And step S302, designing the feedforward filter according to the corrected ideal frequency response curve of the feedforward filter.
In application, after obtaining the modified ideal frequency response curve of the feedforward filter, the type, order and specific filter coefficient of the feedforward filter can be determined according to the modified ideal frequency response curve of the feedforward filter. The filter type may be a Finite Impulse Response (FIR) filter or an Infinite Impulse Response (IIR) filter. And obtaining the filter coefficient which is closest to the ideal frequency response curve of the corrected feedforward filter in the target noise reduction frequency band by various general filter design means.
As shown in fig. 4, in one embodiment, step S301 includes:
step S401, respectively correcting an ideal frequency response curve of a feedforward filter according to frequency response curves of a plurality of different feedback filters, a transfer function from external noise to a standard microphone in an ear canal, a transfer function from a loudspeaker to the standard microphone in the ear canal, a transfer function from the external noise to the feedforward microphone, a transfer function from the external noise to the feedback microphone and a transfer function from the loudspeaker to the feedback microphone, and obtaining corrected ideal frequency response curves of the feedforward filter corresponding to the frequency response curves of the plurality of different feedback filters;
s402, selecting a corrected ideal frequency response curve of the feedforward filter, the flatness of which meets the preset requirement, from the plurality of corrected ideal frequency response curves of the feedforward filter;
step S302 includes:
and S403, designing the feedforward filter according to the corrected ideal frequency response curve of the feedforward filter, wherein the flatness meets the preset requirement.
In applications where the feedback filter is designed in advance, the number of feedback filters meeting the design requirements may be more than one. When two or more feedback filters meeting the design requirements exist, the ideal frequency response curve of the feedforward filter can be corrected according to the frequency response curve and the known parameters of each feedback filter, and the corrected ideal frequency response curve of the feedforward filter corresponding to each feedback filter is obtained. And then selecting a corrected ideal frequency response curve of the feedforward filter, the flatness of which meets the preset requirement, as the finally determined ideal frequency response curve of the corrected feedforward filter.
In application, the frequency response curve generally includes an amplitude-frequency characteristic curve and a phase-frequency characteristic curve, and correspondingly, the ideal frequency response curve of the modified feedforward filter includes an ideal amplitude-frequency characteristic curve and an ideal phase-frequency characteristic curve of the modified feedforward filter.
In one embodiment, the modified ideal frequency response curve of the feedforward filter with flatness meeting the preset requirements comprises:
the amplitude variation in the preset frequency band is larger than a first amplitude threshold and smaller than a second amplitude threshold; and
and the phase variation in the preset frequency band is larger than the first phase threshold and smaller than the second phase threshold.
In another embodiment, the modified ideal frequency response curve of the feedforward filter with flatness meeting the preset requirements comprises:
the absolute value of the slope of each preset octave in the preset frequency band is smaller than the ideal amplitude-frequency characteristic curve of the corrected feedforward filter of the amplitude change rate threshold; and
and the absolute value of the slope of each preset octave in the preset frequency band is smaller than the ideal phase-frequency characteristic curve of the corrected feedforward filter of the phase change rate threshold.
In application, the preset frequency band, the first amplitude threshold, the second amplitude threshold, the first phase threshold, the second phase threshold, the preset octave, the amplitude change rate threshold and the volume value of the phase change rate threshold can be preset according to actual needs. For example, the preset frequency band may be set to 100Hz (hertz) to 300Hz, the preset octave may be set to 1/3 octaves, the amplitude change rate threshold may be set to 4dB per1/3octave (i.e., 4dB per1/3 octaves), and the phase change rate threshold may be set to 15 per1/3octave (i.e., 15 degrees per1/3 octaves).
In one embodiment, the first amplitude threshold is a difference between an average amplitude value and a lower amplitude threshold in a preset frequency band, and the second amplitude threshold is a sum of the average amplitude value and the upper amplitude threshold in the preset frequency band;
the first phase threshold is the difference between the average phase value in the preset frequency band and the lower limit phase threshold, and the second phase threshold is the sum of the average phase value in the preset frequency band and the upper limit phase threshold.
In application, for each modified ideal amplitude-frequency characteristic curve of the feedforward filter, the first amplitude threshold is equal to the difference between the average amplitude value in the preset frequency band in the curve and the preset lower limit amplitude threshold, and the second amplitude threshold is equal to the sum of the average amplitude value in the preset frequency band in the curve and the preset upper limit amplitude threshold. Similarly, for each modified ideal phase characteristic curve of the feedforward filter, the first phase threshold is equal to the difference between the average phase value in the preset frequency band in the curve and the preset lower limit phase threshold, and the second phase threshold is equal to the sum of the average phase value in the preset frequency band in the curve and the preset upper limit phase threshold. The lower limit amplitude threshold, the upper limit amplitude threshold, the lower limit phase threshold and the upper limit phase threshold may be set in advance according to actual needs, for example, the lower limit amplitude threshold and the upper limit amplitude threshold may be set to 8dB (decibel), and the lower limit phase threshold and the upper limit phase threshold may be set to 30 ° (degrees).
As shown in fig. 5, an ideal amplitude-frequency characteristic curve 51 of the feedforward filter (i.e., an ideal amplitude-frequency characteristic curve of the feedforward filter before modification) and an ideal amplitude-frequency characteristic curve 52 of the feedforward filter after modification when noise reduction alone is performed by the feedforward filter are exemplarily shown; the ideal amplitude-frequency characteristic curve 52 of the feedforward filter after correction has large amplitude fluctuation around 80 Hz.
As shown in fig. 6, an ideal phase-frequency characteristic curve 61 of the feedforward filter (i.e., an ideal phase-frequency characteristic curve of the feedforward filter before modification) and an ideal phase-frequency characteristic curve 62 of the feedforward filter after modification when noise reduction alone is performed by the feedforward filter are exemplarily shown; the corrected ideal phase-frequency characteristic curve 62 of the feedforward filter has a large phase fluctuation around 100 Hz.
As shown in fig. 7, in one embodiment, step S301 includes:
step S701, respectively correcting an ideal frequency response curve of a feedforward filter according to a plurality of different sets of transfer functions of external noise to a standard microphone in an ear canal, a transfer function of a loudspeaker to the standard microphone in the ear canal, a transfer function of the external noise to a feedback microphone, a transfer function of the loudspeaker to the feedback microphone, a frequency response curve of the feedback filter and a transfer function of the external noise to the feedforward microphone, and obtaining a plurality of corrected ideal frequency response curves of the feedforward filter corresponding to the plurality of different sets of transfer functions of the external noise to the standard microphone in the ear canal, the transfer function of the loudspeaker to the standard microphone in the ear canal, the transfer function of the external noise to the feedback microphone and the transfer function of the loudspeaker to the feedback microphone;
step S702, selecting a corrected ideal frequency response curve of the feedforward filter, the flatness of which meets the preset requirement, from the plurality of corrected ideal frequency response curves of the feedforward filter;
step S302, including:
and step S703, designing the feedforward filter according to the corrected ideal frequency response curve of the feedforward filter, wherein the flatness meets the preset requirement.
In application, before the known parameters obtained by pre-measurement, the setting position of the feedback microphone of the active noise reduction earphone, the sound hole direction of the feedback microphone, the shape of the sound outlet of the earplug, the setting position, the size and the shape of the leakage hole of the front sound cavity and the acoustic resistance material covering the leakage hole of the front sound cavity need to be designed in advance. These hardware structural designs directly affect the relative magnitude and phase relationship of the transfer function of the external noise to the standard microphone in the ear canal, the transfer function of the speaker to the standard microphone in the ear canal, the transfer function of the external noise to the feedback microphone, and the transfer function of the speaker to the feedback microphone. Therefore, these known parameters can be changed by changing the hardware structure design of the active noise reduction earphone. When two or more different hardware structure designs exist, a set of transfer functions of external noise to a standard microphone in the ear canal, a transfer function of a speaker to a standard microphone in the ear canal, a transfer function of external noise to a feedback microphone and a transfer function of a speaker to a feedback microphone, a frequency response curve of a feedback filter and a transfer function of external noise to a feedforward microphone can be obtained according to measurement respectively, and correcting the ideal frequency response curve of the feedforward filter to obtain the corrected ideal frequency response curve of the feedforward filter corresponding to the transfer function from the external noise to the standard microphone in the ear canal, the transfer function from the loudspeaker to the standard microphone in the ear canal, the transfer function from the external noise to the feedback microphone and the transfer function from the loudspeaker to the feedback microphone. And then selecting a corrected ideal frequency response curve of the feedforward filter, the flatness of which meets the preset requirement, as the finally determined ideal frequency response curve of the corrected feedforward filter.
In one embodiment, step S701 is preceded by:
adjusting the setting position of the feedback microphone and the sound hole direction of the feedback microphone to obtain a plurality of groups of different transfer functions of external noise to a standard microphone in an ear canal, a speaker to the standard microphone in the ear canal, the external noise to the feedback microphone and the speaker to the feedback microphone;
or adjusting the shape of the sound outlet mouth of the earplug to obtain a plurality of different sets of transfer functions of external noise to a standard microphone in the ear canal, a speaker to a standard microphone in the ear canal, an external noise to a feedback microphone and a speaker to a feedback microphone;
or, adjusting the setting position, size, shape or acoustic resistance material covering the leakage hole of the front sound cavity to obtain a plurality of different sets of transfer functions of external noise to the standard microphone in the ear canal, the speaker to the standard microphone in the ear canal, the external noise to the feedback microphone and the speaker to the feedback microphone.
In application, adjusting the setting position of the feedback microphone and the sound hole direction of the feedback microphone, or adjusting the shape of the sound outlet mouth of the earplug, or adjusting the setting position, size and shape of the leakage hole of the front sound cavity or the sound resistance material covering the leakage hole of the front sound cavity directly affects the relative size and phase relationship of the external noise to the standard microphone in the ear canal, the speaker to the standard microphone in the ear canal, the external noise to the feedback microphone and the speaker to the feedback microphone, and further affects the shape of the ideal frequency response curve of the feedforward filter after modification.
In one embodiment, steps S402 and S702 include:
selecting a modified ideal frequency response curve of the feedforward filter, wherein the absolute value of the amplitude variation in a preset frequency band is less than or equal to an amplitude threshold and the absolute value of the phase variation is less than or equal to a phase threshold, from the modified ideal frequency response curves of the feedforward filter; the corrected ideal frequency response curve of the feedforward filter comprises an ideal amplitude-frequency characteristic curve and an ideal phase-frequency characteristic curve of the corrected feedforward filter.
In the application, the operations performed in step S402 and step S702 are the same, and the difference is only that the execution timings of the two are different, step S402 is performed after step S401, and step S702 is performed after step S701; similarly, the operations performed in step S403 and step S703 are the same, except that the timing of performing the two operations is different, and step S403 is performed after step S402, and step S703 is performed after step S702.
As shown in fig. 8, in an embodiment, after step S302, the method further includes:
step S801 is to obtain a modified mixed noise reduction effect curve according to a frequency response curve of the feedback filter, a transfer function of external noise to a standard microphone in an ear canal, a transfer function of a speaker to a standard microphone in an ear canal, a transfer function of external noise to a feedforward microphone, a transfer function of external noise to a feedback microphone, a transfer function of a speaker to a feedback microphone, and an actual frequency response curve of the feedforward filter.
In application, the actual frequency response curve of the feedforward filter is a frequency response curve drawn according to the frequency response of the feedforward filter actually measured by the earphone test system when mixed noise reduction is performed through the feedback filter and the feedforward filter after the feedforward filter is designed according to the corrected ideal frequency response curve of the feedforward filter. The modified mixed noise reduction effect curve is a curve which is calculated according to the frequency response curve of the feedback filter, the transfer function of external noise to a standard microphone in an ear canal, the transfer function of external noise to the feedforward microphone, the transfer function of external noise to the feedback microphone, the transfer function of the speaker to the standard microphone in the ear canal and the actual frequency response curve of the feedforward filter and used for reflecting the mixed noise reduction effect of the feedback filter and the feedforward filter after the feedforward filter is designed according to the modified ideal frequency response curve of the feedforward filter, and when mixed noise reduction is carried out through the feedback filter and the feedforward filter, the modified mixed noise reduction effect curve is obtained. The modified hybrid noise reduction effect curve may include an amplitude-frequency characteristic curve and a phase-frequency characteristic curve.
In one embodiment, the modified mixed noise reduction effect curve is expressed by:
ANC_hybrid＝1-(eb*Hb+Taf*Hf)*Tde/Tae；
eb＝(Tab–Tdb*Hf*Taf)*Nb；
where ANC _ hybrid represents a modified mixed noise reduction effect curve, Hb represents a frequency response curve of the feedback filter, Hf represents an actual frequency response curve of the feedforward filter, Tae represents a transfer function of external noise to a standard microphone in the ear canal, Tde represents a transfer function of a speaker to a standard microphone in the ear canal, Taf represents a transfer function of external noise to the feedforward microphone, Tab represents a transfer function of external noise to the feedback microphone, Tdb represents a transfer function of a speaker to the feedback microphone, Nb represents a noise reduction rate at the feedback microphone when noise reduction alone is performed by the feedback filter, and eb represents noise at the feedback microphone when noise reduction is performed by mixing the feedback filter and the feedforward filter.
In an application, the actual frequency response curve of the feedforward filter may include an actual amplitude-frequency characteristic curve and an actual phase-frequency characteristic curve of the feedforward filter.
As shown in fig. 9, a linear superposition curve 91 of the noise reduction effect of the feedforward filter and the noise reduction effect of the feedback filter and a modified mixed noise reduction effect curve 92 are exemplarily shown.
As shown in fig. 10, an ideal amplitude-frequency characteristic curve 101 of the feedforward filter after adjusting the acoustic resistance material covering the leak hole of the front acoustic cavity and an ideal amplitude-frequency characteristic curve 102 of the feedforward filter after being modified are exemplarily shown; the amplitude fluctuation of the ideal amplitude-frequency characteristic curve 102 of the feedforward filter after the correction is small.
As shown in fig. 11, an ideal phase-frequency characteristic 111 of the feedforward filter and an ideal phase-frequency characteristic 112 of the feedforward filter after adjusting the acoustic resistance material covering the leakage hole of the front acoustic cavity are exemplarily shown; the corrected ideal phase-frequency characteristic curve 112 of the feedforward filter has small phase fluctuation.
According to the method and the device, the ideal frequency response curve of the feedforward filter is modified according to the frequency response curve of the feedback filter, the transfer function of external noise to a standard microphone in an ear canal, the transfer function of a loudspeaker to a standard microphone in the ear canal, the transfer function of external noise to the feedforward microphone, the transfer function of external noise to the feedback microphone and the transfer function of the loudspeaker to the feedback microphone, the feedforward filter is designed according to the modified ideal frequency response curve of the feedforward filter, the feedback filter can be designed independently, then the influence on the ideal frequency response curve of the feedforward filter when the feedback filter is opened for noise reduction is analyzed according to the frequency response curve of the feedback filter and the noise transfer function related to an earphone, the modified ideal frequency response curve of the feedforward filter is obtained, and therefore the mixed noise reduction effect is matched according to the modified ideal frequency response curve of the feedforward filter A desired feedforward filter.
It should be understood that, the sequence numbers of the steps in the foregoing embodiments do not imply an execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.
The embodiment of the present application further provides a filter design device for an active noise reduction earphone, which is used for executing the steps in the filter design method for an active noise reduction earphone. The filter design device of the active noise reduction earphone may be a virtual application (virtual application) in the test equipment, which is run by a processor of the test equipment, or may be the test equipment itself.
As shown in fig. 12, a filter design apparatus 12 of an active noise reduction headphone provided in an embodiment of the present application includes:
a modifying module 121, configured to modify an ideal frequency response curve of the feedforward filter according to a frequency response curve of the feedback filter, a transfer function of the external noise to a standard microphone in the ear canal, a transfer function of the speaker to a standard microphone in the ear canal, a transfer function of the external noise to the feedback microphone, and a transfer function of the speaker to the feedback microphone;
a design module 122 for designing the feedforward filter according to the modified ideal frequency response curve of the feedforward filter.
In one embodiment, the filter design apparatus of the active noise reduction headphone further comprises an adjusting module for:
adjusting the setting position of the feedback microphone and the sound hole direction of the feedback microphone to obtain a plurality of groups of different transfer functions of external noise to a standard microphone in an ear canal, a speaker to the standard microphone in the ear canal, the external noise to the feedback microphone and the speaker to the feedback microphone;
or adjusting the shape of the sound outlet mouth of the earplug to obtain a plurality of different sets of transfer functions of external noise to a standard microphone in the ear canal, a speaker to a standard microphone in the ear canal, an external noise to a feedback microphone and a speaker to a feedback microphone;
or, adjusting the setting position, size, shape or acoustic resistance material covering the leakage hole of the front sound cavity to obtain a plurality of different sets of transfer functions of external noise to the standard microphone in the ear canal, the speaker to the standard microphone in the ear canal, the external noise to the feedback microphone and the speaker to the feedback microphone.
In application, the adjusting module is specifically configured to adjust design parameters such as positions, sizes, shapes, materials, and the like of hardware structures of the active noise reduction earphone when receiving an adjusting instruction input by a user through any human-computer interaction mode supported by the testing device.
In application, each module in the filter design apparatus may be a software program module, may be implemented by different logic circuits integrated in a processor, and may also be implemented by a plurality of distributed processors.
As shown in fig. 13, an embodiment of the present application further provides a test device 13, including: at least one processor 131 (only one processor is shown in fig. 13), a memory 132, and a computer program 133 stored in the memory 132 and executable on the at least one processor 131, the steps of any of the various filter design method embodiments described above being implemented when the computer program 133 is executed by the processor 131.
In an application, the test equipment may include, but is not limited to, a processor, a memory. Those skilled in the art will appreciate that fig. 13 is merely an example of a testing device, and does not constitute a limitation of the testing device, and may include more or less components than those shown, or some components in combination, or different components, such as input output devices, network access devices, etc.
In an Application, the Processor may be a Central Processing Unit (CPU), and the Processor may also be other general purpose processors, 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, and the like. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
In an application, the memory may in some embodiments be an internal storage unit of the test device, such as a hard disk or a memory of the test device. The memory may also be an external storage device of the test equipment in other embodiments, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), etc. provided on the test equipment. Further, the memory may also include both an internal storage unit of the test device and an external storage device. The memory is used for storing an operating system, application programs, a BootLoader (BootLoader), data, and other programs, such as program codes of computer programs. The memory may also be used to temporarily store data that has been output or is to be output.
It should be noted that, for the information interaction, execution process, and other contents between the above-mentioned devices/modules, the specific functions and technical effects thereof are based on the same concept as those of the embodiment of the method of the present application, and reference may be made to the part of the embodiment of the method specifically, and details are not described here.
It will be clear to those skilled in the art that, for convenience and simplicity of description, the foregoing division of the functional modules is merely illustrated, and in practical applications, the above function distribution may be performed by different functional modules according to needs, that is, the internal structure of the device is divided into different functional modules to perform all or part of the above described functions. Each functional module in the embodiments may be integrated into one processing module, or each module may exist alone physically, or two or more modules are integrated into one module, and the integrated module may be implemented in a form of hardware, or in a form of software functional module. In addition, specific names of the functional modules are only used for distinguishing one functional module from another, and are not used for limiting the protection scope of the application. The specific working process of the modules in the system may refer to the corresponding process in the foregoing method embodiment, and is not described herein again.
An embodiment of the present application further provides a testing apparatus, which includes: at least one processor, a memory, and a computer program stored in the memory and executable on the at least one processor, the processor implementing the steps in the above-described various embodiments of the active noise reduction headphone filter design method when executing the computer program.
The embodiment of the present application further provides a computer-readable storage medium, where a computer program is stored, and when the computer program is executed by a processor, the steps in the filter design method embodiments of the active noise reduction earphone described above may be implemented.
The embodiments of the present application provide a computer program product, which, when running on a testing device, enables the testing device to implement the steps in the above embodiments of the filter design method for an active noise reduction earphone when executed.
The integrated module, if implemented in the form of a software functional module and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, all or part of the processes in the methods of the embodiments described above can be implemented by a computer program, which can be stored in a computer-readable storage medium and can implement the steps of the embodiments of the methods described above when the computer program is executed by a processor. Wherein the computer program comprises computer program code, which may be in the form of source code, object code, an executable file or some intermediate form, etc. The computer readable medium may include at least: any entity or device capable of carrying computer program code to the test equipment, recording medium, computer Memory, Read-Only Memory (ROM), Random-Access Memory (RAM), electrical carrier wave signals, telecommunications signals, and software distribution medium. Such as a usb-disk, a removable hard disk, a magnetic or optical disk, etc.
In the above embodiments, the descriptions of the respective embodiments have respective emphasis, and reference may be made to the related descriptions of other embodiments for parts that are not described or illustrated in a certain embodiment.
Those of ordinary skill in the art will appreciate that the various illustrative modules and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware or combinations of computer software and electronic hardware. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
In the embodiments provided in the present application, it should be understood that the disclosed test apparatus and method may be implemented in other ways. For example, the above-described test device embodiments are merely illustrative, and for example, the division of the modules is only one logical functional division, and other divisions may be realized in practice, for example, a plurality of modules or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or modules, and may be in an electrical, mechanical or other form.
The modules described as separate parts may or may not be physically separate, and parts displayed as modules may or may not be physical modules, may be located in one place, or may be distributed on a plurality of network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present application and are intended to be included within the scope of the present application.
Claims (10)
1. A method for designing a filter of an active noise reduction earphone is characterized by comprising the following steps:
modifying the ideal frequency response curve of the feedforward filter according to the frequency response curve of the feedback filter, the transfer function of the external noise to a standard microphone in the ear canal, the transfer function of the loudspeaker to the standard microphone in the ear canal, the transfer function of the external noise to the feedforward microphone, the transfer function of the external noise to the feedback microphone and the transfer function of the loudspeaker to the feedback microphone;
and designing the feedforward filter according to the corrected ideal frequency response curve of the feedforward filter.
2. The method of claim 1, wherein the modifying the ideal frequency response curve of the feedforward filter based on the frequency response curve of the feedback filter, the transfer function of the external noise to a standard microphone in the ear canal, the transfer function of the speaker to a standard microphone in the ear canal, the transfer function of the external noise to the feedforward microphone, the transfer function of the external noise to the feedback microphone, and the transfer function of the speaker to the feedback microphone comprises:
correcting the ideal frequency response curve of the feedforward filter according to the frequency response curves of the plurality of different feedback filters, the transfer function of external noise to a standard microphone in the ear canal, the transfer function of a loudspeaker to the standard microphone in the ear canal, the transfer function of the external noise to the feedforward microphone, the transfer function of the external noise to the feedback microphone and the transfer function of the loudspeaker to the feedback microphone respectively to obtain the corrected ideal frequency response curves of the feedforward filter corresponding to the frequency response curves of the plurality of different feedback filters;
selecting a corrected ideal frequency response curve of the feedforward filter, the flatness of which meets the preset requirement, from the corrected ideal frequency response curves of the feedforward filter;
the designing of the feedforward filter according to the corrected ideal frequency response curve of the feedforward filter comprises the following steps:
and designing the feedforward filter according to the corrected ideal frequency response curve of the feedforward filter, wherein the flatness meets the preset requirement.
3. The method of claim 1, wherein the modifying the ideal frequency response curve of the feedforward filter based on the frequency response curve of the feedback filter, the transfer function of the external noise to a standard microphone in the ear canal, the transfer function of the speaker to a standard microphone in the ear canal, the transfer function of the external noise to the feedforward microphone, the transfer function of the external noise to the feedback microphone, and the transfer function of the speaker to the feedback microphone comprises:
modifying the ideal frequency response curve of the feedforward filter according to a plurality of groups of different transfer functions of external noise to a standard microphone in the ear canal, transfer functions of a loudspeaker to the standard microphone in the ear canal, transfer functions of the external noise to a feedback microphone, transfer functions of the loudspeaker to the feedback microphone, frequency response curves of the feedback filter and transfer functions of the external noise to the feedforward microphone respectively to obtain a plurality of modified ideal frequency response curves of the feedforward filter corresponding to the plurality of groups of different transfer functions of the external noise to the standard microphone in the ear canal, transfer functions of the loudspeaker to the standard microphone in the ear canal, transfer functions of the external noise to the feedback microphone and transfer functions of the loudspeaker to the feedback microphone;
selecting a corrected ideal frequency response curve of the feedforward filter, the flatness of which meets the preset requirement, from the corrected ideal frequency response curves of the feedforward filter;
the designing of the feedforward filter according to the corrected ideal frequency response curve of the feedforward filter comprises the following steps:
and designing the feedforward filter according to the corrected ideal frequency response curve of the feedforward filter, wherein the flatness meets the preset requirement.
4. The filter design method for active noise reduction earphone according to claim 3, wherein the ideal frequency response curve of the feedforward filter is modified according to a plurality of different sets of transfer functions of external noise to the standard microphone in the ear canal, speaker to standard microphone in the ear canal, external noise to feedback microphone and speaker to feedback microphone, and frequency response curves of the feedback filter and external noise to feedforward microphone, respectively, before obtaining a plurality of modified ideal frequency response curves of the feedforward filter corresponding to the plurality of different sets of transfer functions of external noise to the standard microphone in the ear canal, speaker to standard microphone in the ear canal, external noise to feedback microphone and speaker to feedback microphone, the method comprises the following steps:
adjusting the setting position of the feedback microphone and the sound hole direction of the feedback microphone to obtain a plurality of groups of different transfer functions of external noise to a standard microphone in an ear canal, a speaker to the standard microphone in the ear canal, the external noise to the feedback microphone and the speaker to the feedback microphone;
or adjusting the shape of the sound outlet mouth of the earplug to obtain a plurality of different sets of transfer functions of external noise to a standard microphone in the ear canal, a speaker to a standard microphone in the ear canal, an external noise to a feedback microphone and a speaker to a feedback microphone;
or, adjusting the setting position, size, shape or acoustic resistance material covering the leakage hole of the front sound cavity to obtain a plurality of different sets of transfer functions of external noise to the standard microphone in the ear canal, the speaker to the standard microphone in the ear canal, the external noise to the feedback microphone and the speaker to the feedback microphone.
5. The method for designing a filter of an active noise reduction headphone according to any one of claims 2 to 4, wherein the selecting the ideal frequency response curve of the modified feedforward filter with flatness meeting the preset requirement from the ideal frequency response curves of the modified feedforward filters comprises:
selecting a corrected ideal frequency response curve of the feedforward filter, wherein the amplitude variation of the corrected ideal frequency response curve in a preset frequency band is larger than a first amplitude threshold and smaller than a second amplitude threshold, and the phase variation of the corrected ideal frequency response curve is larger than a first phase threshold and smaller than a second phase threshold;
or selecting the modified ideal frequency response curve of the feedforward filter, wherein the absolute value of the slope of each preset octave ideal amplitude-frequency characteristic curve in a preset frequency band is smaller than an amplitude change rate threshold value, and the absolute value of the slope of an ideal phase-frequency characteristic curve is smaller than a phase change rate threshold value, from the plurality of modified ideal frequency response curves of the feedforward filter;
the corrected ideal frequency response curve of the feedforward filter comprises an ideal amplitude-frequency characteristic curve and an ideal phase-frequency characteristic curve of the corrected feedforward filter.
6. A method for designing a filter for an active noise reduction earphone according to any of claims 1 to 4, wherein the ideal frequency response curve of the modified feedforward filter is expressed by:
Hf_target_new＝(Tae/Tde–Hb*Nb*Tab)/(Taf*(1-Hb*Nb*Tdb))；
Nb＝1/(1+Tdb*Hb)；
where Hf _ target _ new represents an ideal frequency response curve of the feedforward filter after correction, Hb represents a frequency response curve of the feedback filter, Tae represents a transfer function of external noise to a standard microphone in the ear canal, Tde represents a transfer function of a speaker to a standard microphone in the ear canal, Taf represents a transfer function of external noise to the feedforward microphone, Tab represents a transfer function of external noise to the feedback microphone, Tdb represents a transfer function of a speaker to the feedback microphone, and Nb represents a noise reduction rate at the feedback microphone when noise reduction alone is performed by the feedback filter.
7. The method for designing a filter of an active noise reduction headphone according to any one of claims 1 to 4, further comprising:
and obtaining a modified mixed noise reduction effect curve according to the frequency response curve of the feedback filter, the transfer function of the external noise to the standard microphone in the ear canal, the transfer function of the loudspeaker to the standard microphone in the ear canal, the transfer function of the external noise to the feedforward microphone, the transfer function of the external noise to the feedback microphone, the transfer function of the loudspeaker to the feedback microphone and the actual frequency response curve of the feedforward filter.
8. The method of claim 7, wherein the modified hybrid noise reduction curve is expressed by the following expression:
ANC_hybrid＝1-(eb*Hb+Taf*Hf)*Tde/Tae；
eb＝(Tab–Tdb*Hf*Taf)*Nb；
where ANC _ hybrid represents a modified mixed noise reduction effect curve, Hb represents a frequency response curve of the feedback filter, Hf represents an actual frequency response curve of the feedforward filter, Tae represents a transfer function of external noise to a standard microphone in the ear canal, Tde represents a transfer function of a speaker to a standard microphone in the ear canal, Taf represents a transfer function of external noise to the feedforward microphone, Tab represents a transfer function of external noise to the feedback microphone, Tdb represents a transfer function of a speaker to the feedback microphone, Nb represents a noise reduction rate at the feedback microphone when noise reduction alone is performed by the feedback filter, and eb represents noise at the feedback microphone when noise reduction is performed by mixing the feedback filter and the feedforward filter.
9. A filter design apparatus for an active noise reduction headphone, comprising:
the correction module is used for correcting the ideal frequency response curve of the feedforward filter according to the frequency response curve of the feedback filter, the transfer function of external noise to a standard microphone in an ear canal, the transfer function of a loudspeaker to the standard microphone in the ear canal, the transfer function of the external noise to the feedback microphone and the transfer function of the loudspeaker to the feedback microphone;
and the design module is used for designing the feedforward filter according to the corrected ideal frequency response curve of the feedforward filter.
10. A test device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that the processor, when executing the computer program, implements the steps of the filter design method of an active noise reducing headphone according to any of the claims 1 to 8.
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| CN114040284A (en) * | 2021-09-26 | 2022-02-11 | 北京小米移动软件有限公司 | Noise processing method, noise processing device, terminal and storage medium |
| CN114040285B (en) * | 2021-09-26 | 2024-02-06 | 北京小米移动软件有限公司 | Method and device for generating feedforward filter parameters of earphone, earphone and storage medium |
| CN114040284B (en) * | 2021-09-26 | 2024-02-06 | 北京小米移动软件有限公司 | Noise processing method, noise processing device, terminal and storage medium |
| CN113868993B (en) * | 2021-09-27 | 2023-06-30 | 上海圳呈微电子技术有限公司 | Method for obtaining full frequency domain filter coefficient |
| CN113868993A (en) * | 2021-09-27 | 2021-12-31 | 上海圳呈微电子技术有限公司 | Method for acquiring full-frequency-domain filter coefficient |
| CN114125632A (en) * | 2021-11-26 | 2022-03-01 | 深圳市逸音科技有限公司 | Filter device of active noise reduction earphone and noise reduction method thereof |
| CN114339517A (en) * | 2021-12-31 | 2022-04-12 | 西安讯飞超脑信息科技有限公司 | Audio simulation method and device, electronic equipment and storage medium |
| CN114866899A (en) * | 2022-05-05 | 2022-08-05 | 重庆物奇微电子有限公司 | Earphone noise reduction method, earphone device and computer readable storage medium |
| CN117156333A (en) * | 2023-02-24 | 2023-12-01 | 荣耀终端有限公司 | Noise reduction method, earphone device and storage medium |
| CN117202071A (en) * | 2023-09-21 | 2023-12-08 | 广东金海纳实业有限公司 | Test method and system of noise reduction earphone |
| CN117202071B (en) * | 2023-09-21 | 2024-03-29 | 广东金海纳实业有限公司 | Test method and system of noise reduction earphone |
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