Noise reduction method and noise reduction earphone based on eardrum pressure estimation

Abstract

The present disclosure provides a noise reduction method and earphone based on the eardrum pressure estimation, where a second error microphone is used for sensing the acoustic field outside an output port of the earphone. Since the pressure at the entrance of the ear canal and ear canal parameters are being determined, the obtained eardrum pressure based on a pressure at the second error microphone and the transfer coefficient may be closer to the actual eardrum pressure felt by the human ear, thereby making the noise reduction signal more representative of the noise reduction effect perceived by the human ear, and enhancing the noise reduction effect.

Description

NOISE REDUCTION METHOD AND NOISE REDUCTION EARPHONE BASED ON EARDRUM PRESSURE ESTIMATION TECHNICAL FIELD

[0001] The present disclosure relates generally to the field of noise reduction, and in particular, to a noise reduction method and a noise reduction earphone.BACKGROUND

[0002] Active noise cancellation (ANC) can achieve noise removal by canceling out sound waves based on the principle of sound wave superposition. Active noise cancellation systems may generally include feedforward and feedback noise cancellation systems. In the feedforward noise cancellation system, a microphone is arranged between a noise source and a receiving point to monitor noise in real time and generate an anti-noise signal, thereby achieving noise removal. In the feedback noise cancellation system, for example, an error microphone is utilized to collect a vibration signal, which is then used as the minimization target to generate a noise cancellation signal, thereby achieving noise removal.

[0003] However, in the existing noise cancellation systems, the noise cancellation signal played by the earphone may not accurately represent the noise reduction results perceived by the human ear, which may lead to poor noise cancellation effect of the earphone.SUMMARY

[0004] The present disclosure provides noise reduction method and earphone based on the eardrum pressure estimation, which may enhance the noise reduction effect of an earphone.

[0005] According to a first aspect, a noise reduction method is described. The method may be performed by an earphone, or by a chip, circuit, or module within the earphone. The noise reduction method includes: collecting a vibration signal via a second error microphone for sensing the acoustic field outside an earbud output port of an earphone; determining a pressure at the second error microphone based on the vibration signal collected by the second error microphone; determining a pressure at an entrance of an ear canal based on the pressure at the second error microphone; determining an eardrum pressure based on a transfer coefficient and the pressure at the entrance of the ear canal, where the transfer coefficient is determined based on an ear canal length and a first attenuation coefficient; determining, based on the eardrum pressure, a noise reduction signal for reducing noise; and playing the noise reduction signal.

[0006] In the embodiments of the present disclosure, since the pressure at the entrance of the ear canal and ear canal parameters are being determined, the obtained eardrum pressure based on a pressure at the second error microphone and the transfer coefficient may be closer to the actual eardrum pressure felt by the human ear, thereby making the noise reduction signal more representative of the noise reduction effect perceived by the human ear, and enhancing the noise reduction effect.

[0007] In a possible design, where the pressure at the entrance of the ear canal is equal to the pressure at the second error microphone; or the pressure at the entrance of the ear canal is equal to a product of the pressure at the second error microphone and a first coefficient.

[0008] In this case, the pressure at the entrance of the ear canal is obtained based on the pressure at one microphone, which is simple to implement and has a relatively low cost.

[0009] In a possible design, the method further includes: collecting a vibration signal via a first error microphone located between a speaker and the earbud output port; and determining a pressure at the first error microphone based on the vibration signal collected by the first error microphone, where determining the pressure at the entrance of the ear canal is further based on the pressure at the first error microphone.

[0010] In a possible design, where the pressure at the entrance of the ear canal is equal to a sum of a product of the pressure at the first error microphone and a second coefficient and a product of the pressure at the second error microphone and a third coefficient.

[0011] In this case, the pressure at the entrance of the ear canal is obtained based on pressures at two microphones, so that the eardrum pressure may be determined more precisely.

[0012] In a possible design, where the transfer coefficient is a first transfer coefficient, and the first transfer coefficient is determined based on a first ear canal length and a first attenuation coefficient that are preset values.

[0013] In this case, the earphone may determine the eardrum pressure more quickly based on the preset values of the ear canal length and attenuation coefficient, thereby improving the noise reduction efficiency of the earphone.

[0014] In a possible design, where the transfer coefficient is a second transfer coefficient, and the second transfer coefficient is determined based on a second ear canal length and a second attenuation coefficient, and the second ear canal length and the second attenuation coefficient are historical average values.

[0015] In this case, the earphone may determine the eardrum pressure more quickly based on the historical average values of the ear canal length and attenuation coefficient, thereby improving the noise reduction efficiency of the earphone.

[0016] In a possible design, where the transfer coefficient is a third transfer coefficient, and the third transfer coefficient is determined based on a third ear canal length and a third attenuation coefficient, and the third ear canal length and the third attenuation coefficient are calculated based on the pressure at the first error microphone, the pressure at the entrance of the ear canal and the pressure at the second error microphone.

[0017] In a possible design, the method further includes: determining a loading impedance based on the pressure at the first error microphone, the pressure at the entrance of the ear canal, and the pressure at the second error microphone; obtaining the third ear canal length and the third attenuation coefficient based on the loading impedance; and determining the third transfer coefficient based on the third ear canal length and the third attenuation coefficient.

[0018] In this case, the earphone determines the eardrum pressure based on the vibration signals collected by the first and the second error microphones, so that the eardrum pressure may be determined more precisely, thereby improving the noise reduction effect of the earphone.

[0019] In a possible design, the method further includes: collecting a vibration signal via a reference microphone located between an earbud inner space and an earphone cover; determining a pressure at the reference microphone based on the vibration signal collected by the reference microphone; determining whether a sealing between the human ear and an earphone meets requirements based on the loadingimpedance; and determining an ambient noise based on the pressure at the first error microphone, the pressure at the second error microphone, and the pressure at the reference microphone, where obtaining the third ear canal length and the third attenuation coefficient based on the loading impedance, includes: obtaining the third ear canal length and the third attenuation coefficient based on the loading impedance in a case where the sealing between the human ear and the earphone meets the requirements and the ambient noise is less than or equal to a first threshold.

[0020] In a possible design, the method further includes: determining a new loading impedance based on a new vibration signal in a case where the sealing between the human ear and the earphone does not meet the requirements, and / or the ambient noise is greater than the first threshold; and determining a new transfer coefficient based on the new loading impedance, where determining the eardrum pressure based on the pressure at the entrance of the ear canal and the transfer coefficient, includes: determining the eardrum pressure based on the pressure at the entrance of the ear canal and the new transfer coefficient.

[0021] In this case, the ambient noise and sealing between the human ear and an earphone may be prechecked before determining the eardrum pressure, thereby improving the noise reduction effect of the earphone.

[0022] In a possible design, where determining the eardrum pressure based on the pressure at the entrance of the ear canal and the transfer coefficient, includes: determining the eardrum pressure based on a first transfer coefficient or a second transfer coefficient in a case where the sealing between the human ear and the earphone does not meet the requirements, and / or in a case where the ambient noise is greater than the first threshold, where the first transfer coefficient is determined based on a first ear canal length and a first attenuation coefficient, and the first ear canal length and the first attenuation coefficient are preset values, and the second transfer coefficient is determined based on a second ear canal length and a second attenuation coefficient, and the second ear canal length and the second attenuation coefficient are historical average values.

[0023] In this case, in a case where the sealing between the human ear and the earphone does not meet the requirements, and / or in a case where the ambient noise is greater than the first threshold, the earphone may determine the eardrum pressure more quickly based on the preset values of the ear canal length and attenuation coefficient, or historical average values of the ear canal length and attenuation coefficient, thereby improving the noise reduction efficiency of the earphone.

[0024] In a possible design, where determining the eardrum pressure based on the pressure at the entrance of the ear canal and the transfer coefficient, includes: determining the eardrum pressure based on the pressure at the entrance of the ear canal and the third transfer coefficient in a case where the value of the third transfer coefficient is usable.

[0025] In this case, the third transfer coefficient is may be checked before determining the eardrum pressure, thereby improving the noise reduction effect of the earphone.

[0026] In a possible design, where determining the eardrum pressure based on the pressure at the entrance of the ear canal and the transfer coefficient, includes: determining the eardrum pressure based on the pressure at the entrance of the ear canal and a fourth transfer coefficient in a case where the value of the third transfercoefficient is not usable, where the fourth transfer coefficient is the new transfer coefficient obtained based on the new vibration signal, a first transfer coefficient determined based on first ear canal length and first attenuation coefficient, or a second transfer coefficient determined based on the second ear canal length and the second attenuation coefficient, the first ear canal length and the first attenuation coefficient are preset values, and the second ear canal length and the second attenuation coefficient are historical average values.

[0027] In this case, in a case where the third transfer coefficient is not usable, the transfer coefficient may be determined by preset values of the ear canal length and attenuation coefficient, or historical average values of the ear canal length and attenuation coefficient, thereby improving the noise reduction efficiency of the earphone.

[0028] According to a second aspect, a noise reduction earphone is described. The noise reduction earphone including: an inner space, an earphone cover, a speaker, a second error microphone and an controller; where the speaker is disposed in the inner space of the earphone, the controller is disposed in the inner space of the earphone, the second error microphone disposed between the speaker and an earbud output port of the earphone; and the second error microphone is configured to collect a vibration signal for sensing acoustic field outside the earbud output port, the controller is configured to determine a pressure at the second error microphone based on the vibration signal collected by the second error microphone, determine a pressure at an entrance of an ear canal based on the pressure at the second error microphone, determine an eardrum pressure based on a transfer coefficient and the pressure at the entrance of the ear canal, and determine a noise reduction signal for reducing noise based on the eardrum pressure, the speaker is configured to play a noise reduction signal.

[0029] In a possible design, the noise reduction earphone further includes: a protective tube disposed beside the earbud output port, and the second error microphone is disposed in the protective tube.

[0030] In a possible design, where the second error microphone is disposed between the earbud output port and the earphone cover, and the second error microphone is protruding from the inner space.

[0031] In a possible design, where the pressure at the entrance of the ear canal is equal to the pressure at the second error microphone; or the pressure at the entrance of the ear canal is equal to a product of the pressure at the second error microphone and a first coefficient.

[0032] In a possible design, the noise reduction earphone further includes: a first error microphone between the speaker and the earbud output port, where the first error microphone is configured to collect a vibration signal, and the controller is further configured to: determine a pressure at the first error microphone based on the vibration signal collected by the first error microphone, where determine the pressure at the entrance of the ear canal is further based on the pressure at the first error microphone.

[0033] In a possible design, where the pressure at the entrance of the ear canal is equal to a sum of a product of the pressure at the first error microphone and a second coefficient and a product of the pressure at the second error microphone and a third coefficient.

[0034] In a possible design, where the transfer coefficient is a first transfer coefficient, and the first transfer coefficient is determined based on a first ear canal length and a first attenuation coefficient that are preset values.

[0035] In a possible design, where the transfer coefficient is a second transfer coefficient, and the second transfer coefficient is determined based on a second ear canal length and a second attenuation coefficient, and the second ear canal length and the second attenuation coefficient are historical average values.

[0036] In a possible design, where the transfer coefficient is a third transfer coefficient, and the third transfer coefficient is determined based on a third ear canal length and a third attenuation coefficient, and the third ear canal length and the third attenuation coefficient are calculated based on the pressure at the first error microphone, the pressure at the entrance of the ear canal and the pressure at the second error microphone.

[0037] In a possible design, the controller is further configured to: determine a loading impedance based on the pressure at the first error microphone, the pressure at the entrance of the ear canal, and the pressure at the second error microphone; obtain the third ear canal length and the third attenuation coefficient based on the loading impedance; and determine the third transfer coefficient based on the third ear canal length and the third attenuation coefficient.

[0038] In a possible design, the noise reduction earphone further includes: a reference microphone located between the inner space and the earphone cover, where the reference microphone is configured to collect a vibration signal, and the controller is further configured to: determine a pressure at the reference microphone based on the vibration signal collected by the reference microphone; determine whether a sealing between the human ear and an earphone meets requirements based on the loading impedance; determine an ambient noise based on the pressure at the first error microphone, the pressure at the second error microphone, and the pressure at the reference microphone; and obtain the third ear canal length and the third attenuation coefficient based on the loading impedance in a case where the sealing between the human ear and the earphone meets the requirements and the ambient noise is less than or equal to a first threshold.

[0039] In a possible design, the controller is further configured to: determine a new loading impedance based on a new vibration signal in a case where the sealing between the human ear and the earphone does not meet the requirements, and / or the ambient noise is greater than the first threshold; and determine a new transfer coefficient based on the new loading impedance; and determine the eardrum pressure based on the pressure at the entrance of the ear canal and the new transfer coefficient.

[0040] In a possible design, the controller is further configured to: determine the eardrum pressure based on a first transfer coefficient or a second transfer coefficient in a case where the sealing between the human ear and the earphone does not meet the requirements, and / or in a case where the ambient noise is greater than the first threshold, where the first transfer coefficient is determined based on a first ear canal length and a first attenuation coefficient, and the first ear canal length and the first attenuation coefficient are preset values, and the second transfer coefficient is determined based on a second ear canal length and a second attenuation coefficient, and the second ear canal length and the second attenuation coefficient are historical average values.

[0041] In a possible design, the controller is further configured to determine the eardrum pressure based on the pressure at the entrance of the ear canal and the third transfer coefficient in a case where the value of the third transfer coefficient is usable.

[0042] In a possible design, the controller is further configured to: determine the eardrum pressure based on the pressure at the entrance of the ear canal and a fourth transfer coefficient in a case where the value of the third transfer coefficient is not usable, where the fourth transfer coefficient is the new transfer coefficient obtained based on the new vibration signal, a first transfer coefficient determined based on first ear canal length and first attenuation coefficient, or a second transfer coefficient determined based on the second ear canal length and the second attenuation coefficient, the first ear canal length and the first attenuation coefficient are preset values, and the second ear canal length and the second attenuation coefficient are historical average values.

[0043] According to a third aspect, a computer-readable storage medium is described. The computer-readable storage medium has instructions stored thereon which, when executed by a noise reduction earphone, cause the noise reduction earphone to perform the method in any one of the possible designs of the first aspect.

[0044] According to a fourth aspect, a computer program product is described. The computer program product stores instructions which, when executed, cause a noise reduction earphone to perform the method in any one of the possible designs of the first aspect.BRIEF DESCRIPTION OF THE DRAWINGS

[0045] For a better understanding of the various described embodiments, reference should be made to the Detailed Description below, in conjunction with the following drawings in which like reference numerals refer to corresponding parts throughout the figures.

[0046] FIG. 1 illustrates a schematic diagram of an example active noise cancellation system.

[0047] FIG. 2 illustrates a relative position relationship between an active noise cancellation earphone and a human ear.

[0048] FIG. 3 illustrates a schematic diagram of an active noise cancellation earphone in accordance with some embodiments of the present disclosure.

[0049] FIG.4 illustrates a schematic diagram of an active noise cancellation earphone in accordance with some embodiments of the present disclosure.

[0050] FIG. 5 illustrates a schematic diagram of an active noise cancellation earphone in accordance with some embodiments of the present disclosure.

[0051] FIG. 6 illustrates a flowchart of a noise reduction method in accordance with some embodiments of the present disclosure.

[0052] FIG. 7 illustrates a schematic diagram of an example of a human ear.

[0053] FIG. 8 illustrates a flowchart of obtaining an eardrum pressure in accordance with some embodiments of the present disclosure.DETAILED DESCRIPTION

[0054] Technical solutions in some embodiments of the present disclosure will be described clearly below with reference to the accompanying drawings.

[0055] Active noise cancellation (ANC) can achieve noise removal by canceling out sound waves based on the principle of sound wave superposition. Active noise cancellation systems generally may includefeedforward and feedback noise cancellation systems. The present disclosure relates to the hybrid (i.e. including both feedforward and feedback) noise cancellation system.

[0056] The composition and noise reduction principle of the hybrid noise cancellation system will be described below in combination with FIGS. 1 and 2.

[0057] FIG. 1 illustrates a schematic diagram of an example active noise cancellation (ANC) system. As shown in FIG. 1, the active noise cancellation system 100 may include a reference microphone 110, an error microphone 120, a controller 130, and a speaker 140.

[0058] The working principle and process of the active noise cancellation system 100 shown in FIG. 1 are as follows.

[0059] The error microphone 120 collects and transmits vibration signals to the controller 130. The vibration signals may contain acoustic field characteristics, such as sound pressure, and particle velocities in different directions.

[0060] The reference microphone 110 collects and transmits noise signals to the controller 130. It should be understood that the noise signals collected by the reference microphone 110 are ambient noise signals, which are usually emitted by undesired noise sources.

[0061] The controller 130 calculates an error cost function based on the vibration signals, predicts a noise reduction signal by using the principle of minimizing the error cost function based on the noise signals, and then outputs the noise reduction signal to the speaker 140. The noise reduction signal may be used to cancel the noise signals. Ideally, the noise reduction signal is the inverse signal of the noise signals. The noise reduction signal may also be referred to as the anti-noise signal. The controller 130 is, for example, an adaptive filter.

[0062] The speaker 140 plays the noise reduction signal from the controller 130.

[0063] The noise signal and the noise reduction signal reach the external auditory canal opening of the human ear through the primary and secondary pathways, respectively.

[0064] The purpose of the controller 130 in predicting the noise reduction signal is to minimize the error cost function of signals reaching the external auditory canal opening of the human ear, which are signals obtained by superimposing the noise signal and the noise reduction signal after passing through the primary path and the secondary path, respectively.

[0065] In the existing active noise cancellation systems, the error microphone 120 generally collects the vibration signals in the first space of the earphone (see below).

[0066] Typically, active noise cancellation systems have a product form of earphones. FIG. 2 illustrates a relative position relationship between an active noise cancellation earphone and a human ear. As shown in FIG.2, a reference microphone 210 is placed outside the earbud’s inner space and is covered by the earphone cover. The reference microphone 210 is configured to collect an ambient noise signal. An error microphone 220 is placed inside the earbud’s inner space and is covered by the earphone cover. The error microphone 220 is configured to collect an error signal after noise cancellation processing. A controller 230 is placed inside the earphone cover and is configured to predict, based on the noise signal and the error signal, a noise reduction signal to be output via the speaker 240. The speaker 240 is placed inside the earphone cover andis configured to play the noise reduction signal.

[0067] It should be understood that in a playback scenario, in addition to the ambient noise signal and the noise reduction signal, sound signals reaching the human ear may also include an effective sound signal, such as an audio signal generated by music or conversations. In this playback scenario, during the process of obtaining the error signal, the effective sound signal is eliminated. For example, the controller 230 eliminates the effective sound signal through signal processing to obtain the residual noise at the error microphone 220 after active noise reduction, i.e., the error signal.

[0068] It should be understood that the eardrum is the organ that collects sound. When sound waves cause the vibration of the eardrum, the information from the eardrum vibration is transmitted to the brain, so that the person perceives the sound. That is, the location of the eardrum is the location of auditory perception.

[0069] In the existing feedback and hybrid noise cancellation systems, the algorithms are targeted to minimize the sound pressure at the error microphone. As the result, the calculated anti-noise provides noise reduction at the error microphone point, while noise reduction at the eardrum is not guaranteed, which may lead to poor noise reduction effect of the earphone.

[0070] In light of this, some embodiments of the present disclosure provide a noise reduction method, in which a noise reduction signal is determined based on an estimation of sound pressure signal at the eardrum. The noise reduction signal may better represent the noise reduction effect perceived by the human ear, thereby improving the noise reduction effect.

[0071] Several possible structures of earphone for achieving the noise reduction method in accordance with some embodiments of the present disclosure will be introduced below. The noise reduction earphone may have a form of in-ear earphones or intra-concha earphones.

[0072] FIG. 3 illustrates a schematic diagram of an active noise cancellation earphone in accordance with some embodiments of the present disclosure.

[0073] As shown in FIG. 3, the earphone 300 includes an inner space 310 and an earphone cover 320, and the inner space 310 is disposed inside the earphone cover 320.

[0074] The inner space 310 includes a speaker 3101, which divides the inner space 310 into a first space and a second space. The first space is a space closer to the eardrum of human ear, while the second space is a space farther away from the eardrum of human ear. The speaker 3101 is configured to play the noise reduction signal to the human ear.

[0075] The inner space 310 further includes a first error microphone 3102 and a second error microphone 3103 disposed in the first space. The first error microphone 3102 is configured to collect the vibration signal inside the first space, and the second error microphone 3103 is configured to collect the vibration signal just outside the earphone’s output port.

[0076] The earphone 300 further includes a reference microphone 330 between the inner space 310 and the earphone cover 320. The reference microphone 330 is configured to collect an ambient noise signal.

[0077] The earphone 300 further includes a controller 3104. The controller 3104 is configured to determine the noise reduction signal based on the vibration signals collected by the reference microphone 330, first error microphone 3102 and the second error microphone 3103. The noise reduction signal is usedto cancel out the noise signal.

[0078] It is understood that the first error microphone and second error microphone may have other names, and the embodiments of the present disclosure do not limit this.

[0079] The earphone 300 collects the vibration signals in the first space and just outside the earphone’s output port by using the first error microphone 3102 and the second error microphone 3103, thereby obtaining the noise reduction signal for active noise cancellation, since the pressure at the entrance of the ear canal and ear canal parameters are being determined, the obtained eardrum pressure based on a pressure at the second error microphone and the transfer coefficient may be closer to the actual eardrum pressure felt by the human ear, thereby making the noise reduction signal more representative of the noise reduction effect perceived by the human ear, and enhancing the noise reduction effect.

[0080] FIG. 4 illustrates a schematic diagram of an active noise reduction earphone in accordance with some embodiments of the present disclosure. In FIG. 4, the positions and functions of the speaker 4101, first error microphone 4102, reference microphone 430 and controller 4104 included in the active noise cancellation earphone 400 are the same as those in FIG. 3, and will not be repeated here. In one possible implementation, the inner space 410 further includes a protective tube 4103 disposed in the first space of the inner space 410, and the second error microphone 41031 is disposed in the protective tube 4103. The size of the protective tube 4103 is limited by the size of the inner space 410, and the diameter of the protective tube 4103 should not be too small to avoid excessive sound attenuation.

[0081] Based on this design, the second error microphone 41031 may be effectively protected by the protective tube 4103, thereby increasing the usage time of the active noise reduction earphone 400.

[0082] FIG. 5 illustrates a schematic diagram of an active noise reduction earphone 500 in accordance with some embodiments of the present disclosure. In FIG. 5, the positions and functions ofthe speaker 5101, first error microphone 5102, reference microphone 530 and controller 5104 included in the active noise cancellation earphone 500 are the same as those in FIG. 3, and will not be repeated here. In one possible implementation, the second error microphone 5103 is disposed between the first space of the inner space 510 and the earphone cover 520, and the second error microphone 5103 is protruding from the first space of the inner space 510, as shown in FIG. 5.

[0083] Based on this design, the second error microphone 5103 may collect the vibration signal at the external auditory canal opening more accurately, and further obtain the noise reduction signal, thereby improving noise reduction effect of the active noise reduction earphone 500.

[0084] FIGS. 3, 4, and 5 are merely examples and not limitations. The position of the second error microphone in the active noise reduction earphone may be flexibly set according to requirements, as long as it is able to collect the vibration signal just outside the earphone’s output port.

[0085] The noise reduction method according to some embodiments of the present disclosure is introduced below in combination with FIGS. 6 and 7.

[0086] FIG. 6 illustrates a flowchart of a noise reduction method in accordance with some embodiments of the present disclosure. The noise reduction method 600 is performed by an earphone which may have, for example, the structure shown in any one of FIG 3, 4, or 5, but the embodiments of the present disclosure arenot limited thereto. As shown in FIG. 6, the noise reduction method 600 includes steps 601 to 604.

[0087] In step 601, the earphone collects vibration signals via a second error microphone for sensing acoustic field outside an earbud output port of the earphone.

[0088] The earphone may collect the vibration signals once or repeatedly with a preset interval. The vibration signal represents a sound wave.

[0089] In one possible implementation, in a case where the earphone is put on by a user, the earphone may automatically play a calibration signal, and at the same time, the vibration signal outside an earbud output port may be collected by the second error microphone. It is noted that a frequency range of the calibration signal may be wide enough, which is conducive to obtaining the extreme frequency of the loading impedance for calculating the eardrum pressure, the detail of which will be described later.

[0090] In another possible implementation, the earphone may be connected to an electronic device either wired or wirelessly (e.g., via Bluetooth), and play an audio signal like music and voice from the electronic device. At the same time, the earphone may collect the vibration signal via the second error microphone. In this way, the earphone may not be required to automatically play the calibration signal.

[0091] In step 602, the earphone determines a pressure at the second error microphone based on the vibration signal collected by the second error microphone.

[0092] In step 603, the earphone determines a pressure at an entrance of an ear canal based on the pressure at the second error microphone.

[0093] In step 604, earphone determines an eardrum pressure based on a transfer coefficient and the pressure at the entrance of the ear canal, where the transfer coefficient is determined based on an ear canal length and a first attenuation coefficient.

[0094] In step 605, the earphone determines, based on the eardrum pressure, a noise reduction signal for canceling a noise signal.

[0095] In step 606, the earphone plays the noise reduction signal to the human ear.

[0096] In the noise reduction method of the embodiments of the present disclosure, since pressure at the entrance of the ear canal and ear canal parameters are being determined, the obtained eardrum pressure based on a pressure at the second error microphone and the transfer coefficient may be closer to the actual eardrum pressure felt by the human ear, thereby making the noise reduction signal more representative of the noise reduction effect perceived by the human ear, and enhancing the noise reduction effect.

[0097] It is understood that the noise reduction method of the present disclosure may be executed automatically or after a noise reduction mode of the earphone is enabled by a user.

[0098] In one possible implementation, in a case where the earphone is inserted in the ear, it may automatically start collect vibration signal. In this way, the noise reduction processing of the earphone will not be perceived by the user, so that the user will not be disturbed.

[0099] In another possible implementation, the earphone includes a noise reduction control. In a case where the noise reduction control is operated by a user, the noise reduction mode of the earphone starts, and the earphone may start to collect the vibration signal. In this way, a more flexible choice may be provided for the user. For example, using the noise reduction mode may provide better playback effects, while notusing the noise reduction mode may reduce the power consumption of the earphone.

[0100] In some embodiments of the present disclosure, the eardrum pressure may be determined in the multiple ways, which will be described below.

[0101] In a possible implementation, the eardrum pressure may be determined based on a pressure at an entrance of an ear canal and a transfer coefficient, and the pressure at an entrance of an ear canal may be determined based on the pressure at the second error microphone.

[0102] The transfer coefficient is the ratio between the spectra of the pressure at the eardrum and the pressure at the ear canal opening.

[0103] In this case, the eardrum pressure may be obtained based on the pressure at the entrance of the ear canal, and the pressure at the entrance of the ear canal is determined based on the vibration signal collected by the second error microphone. In this way, the eardrum pressure may be obtained through further calculation, so that the eardrum pressure may be determined more precisely, thereby enhancing the noise reduction effect of the earphone.

[0104] Depending on different structures of the earphone, the pressure at the entrance of the ear canal may be determined in different ways, which will be described below.

[0105] In a possible implementation, the pressure at the second error microphone may be determined as the pressure at entrance of the ear canal, which is, for example, applicable to the active noise reduction earphone 300 shown in FIG. 3.

[0106] For example, the pressure at the second error microphone is denoted as pout, and the pressure at the entrance of the ear canal pemay be expressed as pe= pout.

[0107] In another possible implementation, a second error microphone is arranged inside the protective tube, which is, for example, applicable to the active noise reduction earphone 400 shown in FIG. 4. Because the second error microphone is disposed inside the protective tube, the pressure at the entrance of the ear canal may be obtained more accurately by multiplying the pressure at the second error microphone by the first coefficient.

[0108] For example, the pressure at the second error microphone is denoted as pout, and the pressure at the entrance of the ear canal may be expressed as pe= poutor pe= poutcos(k x I), where cos (A: x Z) is the first coefficient, k is a complex wavenumber, and I is a length of the protective tube. The complex wavenumber may be calculated by using the formulawhere c is the sound velocity, f is frequency, i is imaginary unit, and «( ) is a real function characterizing the attenuation within the protective tube. a( / ) may be estimated using theoretical formulas for thermal and viscous losses within the tube or measured experimentally.

[0109] The above examples only require one microphone to estimate the pressure at the ear canal entrance, which is simple to implement and has a relatively low cost.

[0110] In another possible implementation, the pressure at the entrance of the ear canal may be determined based on the pressures at the first and the second error microphones. For example, the pressure at the entrance of the ear canal may be determined as the sum of a product of the pressure at the second error microphone and a second coefficient and a product of the pressure at the first error microphone and a third coefficient.For example, this manner may be applicable to the active noise reduction earphone 500 shown in FIG. 5.

[0111] For example, the pressure at the second error microphone is denoted as pout, the pressure at the first error microphone is denoted as PfC, and the pressure at the entrance of the ear canal may be expressed as pe= x pout+ a2x pfC, where a- represents the second coefficient, and a2represents the third coefficient. For example, a2and a2are constants, and may be determined based on previous experimental results. Another choice is to consider one of or both arand a2to be dependent on frequency. These dependences may be obtained by fitting experimental results.

[0112] The transfer coefficient mentioned above may be obtained in different ways, which will be described below.

[0113] In a first design, the transfer coefficient may be a first transfer coefficient, and the first transfer coefficient is determined based on a first ear canal length and a first attenuation coefficient. The first ear canal length and the first attenuation coefficient are preset values. The preset value of the ear canal length may be determined based on the average ear canal length of a human. For example, 2.5 cm or value close to 2.5 cm may be used as the preset ear canal length. The preset value of the attenuation coefficient may be found in papers. Another option is to estimate it by analytical formulas for the thermal and viscous losses in a tube, cone or another model. Another option is to measure it somehow for a number of people and to use the average result as the preset value.

[0114] FIG. 7 illustrates a schematic diagram of an example of a human ear. As is shown in FIG. 7, the ear canal length is a distance between the entrance of the ear canal and the eardrum.

[0115] In this case, the earphone may determine the eardrum pressure more quickly based on the preset values of the ear canal length and attenuation coefficient, thereby improving the noise reduction efficiency of the earphone.

[0116] In a second design, the transfer coefficient may be a second transfer coefficient, and the second transfer coefficient is determined based on a second ear canal length and a second attenuation coefficient. The second ear canal length and the second attenuation coefficient are historical average values. The historical average value is calculate from the historical values stored from the first to the last time that user use the earphone.

[0117] In this case, the earphone may determine the eardrum pressure more quickly based on the historical average values of the ear canal length and attenuation coefficient, thereby improving the noise reduction efficiency of the earphone.

[0118] In a third design, the transfer coefficient may be a third transfer coefficient, and the third transfer coefficient is determined based on a third ear canal length and a third attenuation coefficient. The third ear canal length and the third attenuation coefficient are calculated based on the pressure at the second error microphone, the pressure at the ear canal entrance, and the pressure at the first error microphone .

[0119] In the third design, for example, the noise reduction method may further include: determining a loading impedance based on the pressure at the first error microphone, the pressure at the entrance of the ear canal, and the pressure at the second error microphone; obtaining the third ear canal length and the third attenuation coefficient based on the loading impedance analysis; and determining the third transfercoefficient based on the third ear canal length and the third attenuation coefficient.

[0120] In this case, the earphone determines the eardrum pressure based on the vibration signals collected by the first and the second error microphones, so that the eardrum pressure may be determined more precisely, thereby improving the noise reduction effect of the earphone.

[0121] It should be noted that the loading impedance is a complex number composed of resistance and reactance (including inductive reactance and capacitive reactance). In some simple cases, the loading impedance may be a fixed value, but in more complex situations, it may vary with factors such as frequency and operating conditions.

[0122] For example, the pressure at the second error microphone is denoted as pout, the estimated pressure at the entrance of the ear canal is denoted as pe, and the pressure at the first error microphone is denoted as PfC. The loading impedance may be expressed as Zload

[0123] For example, the third ear canal length may be determined in multiple ways. In a possible implementation, the third ear canal length may be calculated using the formula I — — — , where fmaxis the first maximum frequency of the loading impedance, and c is the sound velocity. In another possible implementation, the third ear canal length may also be calculated using the formula I — — — , where fminis the first minimum frequency of the loading impedance. In another possible implementation, the third ear canal length may be calculated using the formula >neighboring local minima or two neighboring local maxima of the loading impedance respectively. Additionally, the third ear canal length may also be determined based on the extrema positions of the loading impedance and the number of wavelengths required for each ear canal length. It should be noted that the calculated ear canal length is an effective length and may differ from the actual length of the ear canal.

[0124] For example, the third attenuation coefficient may be considered to be constant or dependent on frequency and provide good correspondence of the measured Zl'oadto the value given by some model of the ear canal. For example, it may be choose in such a way that it provides the necessary widths of a chosen set of minima of Zl'oad. For example, after Zoadis measured, we can find its first minimum (Zoad)minand the frequency A of the first minimum. Then we find the frequency width of the first minimum. Similar frequency width may be calculated from the chosen model of the ear canal. The third attenuation coefficient should be chosen in such a way that to provide a good coincidence between the minimum width obtained from the measured Zl'oadand the corresponding theoretical value. Following these steps, we obtain a constant value of the attenuation coefficient by some algebraic formula derived in prior, which is more effective than fitting. Another way to determine the third attenuation coefficient may be modified to provide necessary widths of a number of the minima (say, the first one and the second one). Proposing some model of the ear canal, the theoretical formulas for the attenuation coefficient providing the necessary minima’s width may be derived. The third attenuation coefficient may be set to be constant and equal to some average of the calculated values, or the third attenuation coefficient may be considered to be some preset function of frequency and take necessary values at the chosen minima.

[0125] Considering that the pressures at the first and the second error microphone are temporarily measured when the user wears the earphone, in practical applications, the loading impedance depends on the way of the user wearing the earphone. For example, the loading impedance measured when the earphone is tightly inserted into the ear canal is different from that measured when the earphone is gently inserted into the ear canal.

[0126] To improve the noise reduction effect, a pre-check operation is introduced. After obtaining the loading impedance, a pre-check is applied to determine whether the loading impedance is applicable, that is, whether the third transfer coefficient obtained based on the loading impedance meets the requirements. For example, whether a sealing between the human ear and the earphone meets the requirements is checked based on the loading impedance, and then a pressure at the reference microphone is collected. The reference microphone located between an inner space and an earphone cover. Subsequently, the ambient noise is determined based on the pressure at the second error microphone, the pressure at the first error microphone, and the pressure at the reference microphone. In a case where the sealing between the human ear and the earphone meets the requirements and the ambient noise is less than or equal to the first threshold, it indicates that the loading impedance is applicable, and the subsequent processing may be performed using this loading impedance. Otherwise, in a case where the sealing between the human ear and the earphone does not meet the requirements and / or the ambient noise is greater than the first threshold, it indicates that if the loading impedance is used for further processing to perform noise reduction, a good active noise reduction result may not be achieved. The first threshold is a value based on experimental tests. For example, the value may depend on the signals at the first and / or second error microphones, i.e. the pre-check is a comparison of the signals at the reference microphone and the first or / and second earphones. In this case, other methods may be used for noise reduction.

[0127] In the method 600, the eardrum pressure is calculate based on the pressure at the second error microphone. In a possible implementation, the pressure at the second error microphone may be used as the eardrum pressure.

[0128] In this way, the pressure at the second error microphone may be used as the eardrum pressure directly, which may be a simple process that saves the power consumption of the earphone.

[0129] FIG. 8 illustrates a flowchart of a process of obtaining an eardrum pressure in accordance with some embodiments of the present disclosure. The process includes steps 801 to 808.

[0130] In step 801, the pressures at the first and the second error microphone, and the pressure at the entrance of the ear canal are obtained.

[0131] In step 802, a loading impedance is determined based on the pressures at the first and the second error microphone and the pressure at the entrance of the ear canal.

[0132] In step 803, whether a sealing between the human ear and the earphone meets the requirements is determined based on the loading impedance.

[0133] For example, the loading impedance in the low frequency range may be analyzed to determine a leakage type, which may include high leakage and low leakage. The low leakage indicates that the sealing between the human ear and the earphone meets the requirements, meaning that there is a good sealingbetween the human ear and the earphone. The high leakage indicates that the sealing between the human ear and the earphone is poor. For example, the high leakage may mean that there exists a slit through which air may flow between the ear canal and the surrounding space.

[0134] If the sealing between the human ear and the earphone does not meet the requirements, the process may be restarted from the step 801 to determine the pressure at the first and the second error microphone, and the pressure at the entrance of the ear canal.

[0135] In a possible implementation, an audio signal may be automatically played through the earphone after the user inserted or reinserted the earphone. Then, a new vibration signal may be collected through the earphone again. Based on the new vibration signal, a new loading impedance may be determined. In a same way as step 803, the sealing between the human ear and the earphone may be checked based on the new loading impedance. The earphone may repeat the check until the sealing between the human ear and the earphone meets the requirements. Then, the corresponding loading impedance may be used for subsequent processing.

[0136] If the sealing between the human ear and the earphone meets the requirements, the following steps may be performed.

[0137] In step 804, an ambient noise is determined based on the pressures at the first and the second error microphones, and the pressure at the reference microphone.

[0138] In step 805, whether the ambient noise is less than or equal to the first threshold is determined.

[0139] If the ambient noise is greater than the first threshold, the process starts again from the step 801 to determine the pressure at the fist and the second error microphone, and the pressure at the entrance of the ear canal. If the ambient noise is less than or equal to the first threshold, the process continues to the step 806 to determine the third transfer coefficient based on the current loading impedance.

[0140] It should be understood that in the example shown in FIG. 8, the loading impedance is calculated first, and then the ambient noise is calculated only in a case where the sealing between the human ear and the earphone meets the requirements. In another possible implementation, the ambient noise may be calculated first, and the loading impedance may be calculated in a case where the ambient noise is less than or equal to the first threshold. Alternatively, both the loading impedance and the ambient noise may be calculated simultaneously and checked at the same time. The embodiments of the present disclosure do not limit the execution sequence.

[0141] It should also be understood that FIG. 8 only shows one possible implementation. In other possible implementations, if the sealing between the human ear and the earphone does not meet the requirements, and / or the ambient noise is greater than the first threshold, the first design or the second design mentioned above may also be adopted.

[0142] For example, after the step 803 or step 805, if the sealing between the human ear and the earphone does not meet the requirements, and / or the ambient noise is greater than the first threshold, the first transfer coefficient may be obtained, and then the eardrum pressure may be obtained based on the first transfer coefficient and the pressure at the entrance of the ear canal. The first transfer coefficient is determined based on the first ear canal length and the first attenuation coefficient that are preset values. In this case, theearphone may determine the eardrum pressure more quickly based on the preset values of the ear canal length and attenuation coefficient, thereby improving the noise reduction efficiency of the earphone.

[0143] For example, after the step 803 or step 805, if the sealing between the human ear and the earphone does not meet the requirements, and / or the ambient noise is greater than the first threshold, the second transfer coefficient may be obtained, and then the eardrum pressure may be obtained based on the second transfer coefficient and the pressure at the entrance of the ear canal. The second transfer coefficient is determined based on the second ear canal length and the second attenuation coefficient that are historical average values. In this case, the earphone may determine the eardrum pressure more quickly based on the historical average values of the ear canal length and attenuation coefficient, thereby improving the noise reduction efficiency of the earphone.

[0144] In addition, a second threshold may be preset to limit the count of the earphone acquiring the vibration signal. The earphone may perform the process shown in FIG. 8, and if the count of the earphone acquiring the vibration signal is greater than or equal to the second threshold, the earphone adopt the first or second design mentioned above.

[0145] In a possible implementation, the second threshold may be preset to different values based on the requirements for noise cancellation accuracy or efficiency of the earphone. For example, for an earphone with high noise cancellation accuracy requirements, the second threshold may be preset to a large value, in this way, the earphone is allowed to multiple collections of vibration signal to achieve more accurate noise cancellation results. For an earphone with high noise cancellation efficiency requirements, the second threshold may be preset to a small value. In a case where a count of the earphone collecting the vibration signal exceeds the second threshold, the transfer coefficient is directly obtained using a preset value or historical average value to quickly generate a noise cancellation result.

[0146] In any possible implementation described above, after the ear canal length and attenuation coefficient are obtained, the transfer coefficient may be obtained based on the ear canal length and attenuation coefficient. For example, assuming that the ear canal length is represented by I, and the attenuation coefficient is represented by a(f)~, the transfer coefficient may be calculated by the formula K(f) * where c is the sound velocity, is frequency, i is imaginary unit. In this formula,the ear canal is simulated by a tube with a constant cross-section. Additionally, the ear canal may also be simulated using frustums with different size.

[0147] It should be understood that the transfer coefficient may depend on the individual characteristics of the ear canal and the depth at which the earphone is inserted into the ear canal. That is, the transfer coefficient may change each time the user wears the earphone. Therefore, the transfer coefficient needs to be calculated each time the user wears the earphone.

[0148] If the first design or the second design mentioned above is adopted, after obtaining the first transfer coefficient through the first design or obtaining the second transfer coefficient through the second design, the eardrum pressure may be determined based on the pressure at the entrance of the ear canal and the obtained transfer coefficient (the first transfer coefficient or the second transfer coefficient).

[0149] If the third design mentioned above is adopted, after obtaining the third transfer coefficient throughthe third design, the eardrum pressure may be determined based on the pressure at the entrance of the ear canal and the third transfer coefficient. Alternatively, a post-check operation may be applied firstly to verify the usability of the third transfer coefficient. For example, whether the value of the third transfer coefficient is usable and has not expired may be determined first. For example, the value of the third transfer coefficient is usable may be illustrates by whether the value of the third transfer coefficient is within the preset range. If the value of the third transfer coefficient is usable, the eardrum pressure may be determined based on the obtained pressure at the entrance of the ear canal and the third transfer coefficient. If the value of the third transfer coefficient is not usable, for example, the frequency distance between the neighboring maxima or minima doesn’t correspond to realistic ear canal lengths, then the third transfer coefficient may be recalculated, or the first or second transfer coefficient mentioned above may be adopted for calculating the eardrum pressure.

[0150] Referring to the process shown in FIG. 8, after the step 806, the following steps may be executed:

[0151] In step 807, whether the third transfer coefficient is usable and has not expired is determined.

[0152] If the third transfer coefficient is not usable and / or has expired, the process may be restarted from the step 801 to determine the pressure at the first and the second error microphone, and the pressure at the entrance of the ear canal.

[0153] In a possible implementation, an audio may be automatically played through the earphone to prompt the user to remove and reinsert the earphone. Then, a new vibration signal may be obtained, and a new third transfer coefficient may be determined based on the new vibration signal. After obtaining the new third transfer coefficient, the earphone may check whether the new third transfer coefficient is usable. The earphone may repeatedly obtain and check the new third transfer coefficient until the third transfer coefficient is usable. Then the process proceeds to the step 808.

[0154] If the third transfer coefficient is usable and has not expired, the process proceeds to the step 808 to determine the eardrum pressure based on the pressure at the entrance of the ear canal and the third transfer coefficient.

[0155] It should be understood that FIG. 8 only shows one possible implementation. In other possible implementations, if the third transfer coefficient is not usable and / or has expired, that is, when the third transfer coefficient obtained by using the third design is unavailable, the first design or the second design mentioned above may be adopted to obtain the eardrum pressure.

[0156] For example, if it is determined in the step 807 that the third transfer coefficient is not usable or has expired, the first transfer coefficient may be obtained, and the eardrum pressure may be obtained based on the first transfer coefficient and the pressure at the entrance of the ear canal; or, the second transfer coefficient may be obtained, and then the eardrum pressure may be obtained based on the second transfer coefficient and the pressure at the entrance of the ear canal.

[0157] Since the first and the second design have been introduced above, they will not be repeated here.

[0158] In addition, the earphone may obtain a new third transfer coefficient in the process shown in FIG.8. If the count of the earphone acquiring the vibration signal is greater than or equal to the second threshold, the earphone may adopt the first or second design mentioned above.

[0159] In addition, if the first design or the second design mentioned above is adopted, the first transfer coefficient or the second transfer coefficient may be stored in a memory. If the third design is adopted, when the value of the third transfer coefficient is usable, the third transfer coefficient may be stored in the memory.

[0160] In addition, steps 801-808 may be performed with a preset time period. For example, the process may be repeated every 30 seconds.

[0161] How to determine the eardrum pressure is introduced below.

[0162] In a possible implementation, the product of the pressure at the entrance of the ear canal and the transfer coefficient may be subjected to an inverse Fourier transform processing to obtain the eardrum pressure time signal.

[0163] Furthermore, after determining the eardrum pressure through the above process, whether the eardrum pressure conforms to the actual situation may be determined.

[0164] If the value of the eardrum pressure is not in line with the actual situation, the process may restart from the step 801 to determine the pressures at the first and the second error microphone, and the pressure at the entrance of the ear again.

[0165] In a possible implementation, an audio signal may be automatically played through the earphone after the user reinserted the earphone. By recalculating the eardrum pressure based on the re-collected vibration signal, the noise reduction effect of the earphone may be enhanced.

[0166] If the value of the eardrum pressure is in line with the actual situation, the obtained eardrum pressure may be used as a target function for the chosen active noise cancelation algorithm. However, target signal is minimized in in most ANC algorithms. Some embodiments of present disclosure calculate the antinoise signal based on the obtained eardrum pressure, for example, using an adaptive filter. In this way, when the eardrum pressure signal is the target one, the user may feel the ANC effect better.

[0167] It should be understood that FIG. 8 only shows one possible implementation. In another possible implementation, if the value of the eardrum pressure is not in line with the actual situation, the pressure at the ear canal entrance may be set as the eardrum pressure. In this case, the earphone may determine the eardrum pressure more quickly based on the pressure at the ear canal entrance, thereby improving the noise reduction efficiency of the earphone.

[0168] It should also be noted that in order to achieve a more accurate noise reduction effect, the vibration signal collected by the microphone may be as close as possible to the auditory perception position of the human ear based on the principle of active noise reduction and the actual physical meaning of the error microphone, thereby improving the noise reduction effect. Therefore, the embodiments of the present disclosure is not limited to active noise reduction earphone, but may also be applied to other active noise reduction fields.

[0169] The noise reduction method provided in the embodiments of the present disclosure are described in detail above with reference to FIGS. 1 to 8. Next, the noise reduction earphone in the embodiments of the present disclosure will be described in detail below.

[0170] The noise reduction earphone may be used to realize the functions of the noise reduction earphone in the above method embodiments, and therefore may also achieve the beneficial effects of the above methodembodiments. In the embodiments of the present disclosure, the noise reduction earphone may be a noise reduction earphone as shown in any of FIGS. 3 to 5.

[0171] The noise reduction earphone including: an inner space, an earphone cover, a speaker, a second error microphone and an controller; where the speaker is disposed in the inner space of the earphone, the controller is disposed in the inner space of the earphone, the second error microphone disposed between the speaker and an earbud output port of the earphone; and the second error microphone is configured to collect a vibration signal for sensing acoustic field outside the earbud output port, the controller is configured to determine a pressure at the second error microphone based on the vibration signal at the second error microphone, determine a pressure at an entrance of an ear canal based on the pressure at the second error microphone, determine an eardrum pressure based on a transfer coefficient and the pressure at the entrance of the ear canal, and determine a noise reduction signal for reducing noise based on the eardrum pressure, the speaker is configured to play a noise reduction signal.

[0172] It will be understood that, the controller in the embodiments of the present disclosure may be a central processing unit, or may be a general-purpose processor, a digital signal processor, an application specific integrated circuit, a field programmable gate array, or any other programmable logic device, a transistor logic device, a hardware component or any combination thereof. The general-purpose processor may be a microprocessor, or any conventional processor.

[0173] Some embodiments of the present disclosure provide a computer-readable storage medium (e.g., a non-transitory computer-readable storage medium). The computer-readable storage medium has instructions stored thereon which, when executed by a noise reduction earphone, cause the noise reduction earphone to perform the noise reduction method in any of the above embodiments.

[0174] Some embodiments of the present disclosure provide a computer program product. The computer program product stores instructions which, when executed, cause a noise reduction earphone to perform the noise reduction method in any of the above embodiments.

[0175] In the present disclosure, the terms “a”, “an” and “one” are defined to mean “at least one”, that is, these terms do not exclude a plural number of items, unless stated otherwise.

[0176] In the present disclosure, terms such as “substantially”, “generally” and “about”, which modify a value, condition or characteristic of a feature of an exemplary embodiment, should be understood to mean that the value, condition or characteristic is defined within tolerances that are acceptable for the proper operation of this exemplary embodiment for its intended application.

[0177] In the present disclosure, unless stated otherwise, the terms “connected” and “coupled”, and derivatives and variants thereof, refer herein to any structural or functional connection or coupling, either direct or indirect, between two or more elements. For example, the connection or coupling between the elements can be acoustical, mechanical, optical, electrical, thermal, logical, or any combinations thereof.

[0178] In the present disclosure, expressions such as “match”, “matching” and “matched”, including variants and derivatives thereof, are intended to refer herein to a condition in which two or more elements are either the same or within some predetermined tolerance of each other. That is, these terms are meant to encompass not only “exactly” or “identically” matching the two elements but also “substantially”,“approximately” or “subjectively” matching the two or more elements, as well as providing a higher or best match among a plurality of matching possibilities.

[0179] In the present disclosure, the expression “based on” is intended to mean “based at least partly on”, that is, this expression can mean “based solely on” or “based partially on”, and so should not be interpreted in a limited manner. More particularly, the expression “based on” can also be understood as meaning “depending on”, “representative of’, “indicative of’, “associated with” or similar expressions.

[0180] In the present disclosure, the terms "system" and "network" may be used interchangeably in embodiments of this disclosure. "At least one" means one or more, and "a plurality of means two or more. The term "and / or" describes an association relationship of associated objects, and indicates that three relationships may exist. For example, A and / or B may indicate the following three cases: Only A exists, both A and B exist, and only B exists, where A and B may be singular or plural. The character " / " usually indicates an "or" relationship between associated objects. "At least one of the following items (pieces)" or a similar expression thereof indicates any combination of these items, including a single item (piece) or any combination of a plurality of items (pieces). For example, "at least one of A, B, or C" includes A, B, C, A and B, A and C, B and C, or A, B, and C, and "at least one of A, B, and C" may also be understood as including A, B, C, A and B, A and C, B and C, or A, B, and C. In addition, unless otherwise specified, ordinal numbers such as "first" and "second" in embodiments of this disclosure are used to distinguish between a plurality of objects, and are not used to limit a sequence, a time sequence, priorities, or importance of the plurality of objects.

[0181] A person skilled in the art should understand that embodiments of the present disclosure may be provided as a method, an earphone (or system), computer-readable storage medium, or a computer program product. Therefore, this disclosure may use a form of a hardware-only embodiment, a software-only embodiment, or an embodiment with a combination of software and hardware. Moreover, this disclosure may use a form of a computer program product that is implemented on one or more computer-usable storage media (including but not limited to a disk memory, an optical memory, and the like) that include computer-usable program code.

[0182] This disclosure is described with reference to the flowcharts and / or block diagrams of the method, the device (system), and the computer program product. It should be understood that computer program instructions may be used to implement each process and / or each block in the flowcharts and / or the block diagrams and a combination of a process and / or a block in the flowcharts and / or the block diagrams. The computer program instructions may be provided for a general-purpose computer, a dedicated computer, an embedded processor, or a processor of another programmable data processing device to generate a machine, so that the instructions executed by the computer or the processor of the another programmable data processing device generate an earphone for implementing a specific function in one or more procedures in the flowcharts and / or in one or more blocks in the block diagrams.

[0183] The computer program instructions may alternatively be stored in a computer-readable memory that can indicate a computer or another programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate an artifact that includes aninstruction earphone. The instruction earphone implements a specific function in one or more procedures in the flowcharts and / or in one or more blocks in the block diagrams.

[0184] The computer program instructions may alternatively be loaded onto a computer or another programmable data processing device, so that a series of operations and steps are performed on the computer or the another programmable device, so that computer-implemented processing is generated. Therefore, the instructions executed on the computer or the another programmable device provide steps for implementing a specific function in one or more procedures in the flowcharts and / or in one or more blocks in the block diagrams.

[0185] It is clearly that a person skilled in the art can make various modifications and variations to this disclosure without departing from the scope of this disclosure. This disclosure is intended to cover these modifications and variations of this disclosure provided that they fall within the scope of protection defined by the following claims and their equivalent technologies.

Claims

CLAIMS1. A noise reduction method, comprising:collecting a vibration signal via a second error microphone for sensing acoustic field outside an earbud output port of an earphone;determining a pressure at the second error microphone based on the vibration signal collected by the second error microphone;determining a pressure at an entrance of an ear canal based on the pressure at the second error microphone;determining an eardrum pressure based on a transfer coefficient and the pressure at the entrance of the ear canal, wherein the transfer coefficient is determined based on an ear canal length and a first attenuation coefficient;determining, based on the eardrum pressure, a noise reduction signal for reducing noise; and playing the noise reduction signal.

2. The noise reduction method of claim 1, wherein the pressure at the entrance of the ear canal is equal to the pressure at the second error microphone; orthe pressure at the entrance of the ear canal is equal to a product of the pressure at the second error microphone and a first coefficient.

3. The noise reduction method of claim 1, further comprising:collecting a vibration signal via a first error microphone located between a speaker and the earbud output port; anddetermining a pressure at the first error microphone based on the vibration signal collected by the first error microphone, whereindetermining the pressure at the entrance of the ear canal is further based on the pressure at the first error microphone.

4. The noise reduction method of claim 3, wherein the pressure at the entrance of the ear canal is equal to a sum of a product of the pressure at the first error microphone and a second coefficient and a product of the pressure at the second error microphone and a third coefficient.

5. The noise reduction method of any of claims 1 to 4, wherein the transfer coefficient is a first transfer coefficient, and the first transfer coefficient is determined based on a first ear canal length and a first attenuation coefficient that are preset values.

6. The noise reduction method of any of claims 1 to 4, wherein the transfer coefficient is a second transfer coefficient, and the second transfer coefficient is determined based on a second ear canal length and a second attenuation coefficient, and the second ear canal length and the second attenuation coefficient arehistorical average values.

7. The noise reduction method of any of claims 1 to 4, wherein the transfer coefficient is a third transfer coefficient, and the third transfer coefficient is determined based on a third ear canal length and a third attenuation coefficient, and the third ear canal length and the third attenuation coefficient are calculated based on the pressure at the first error microphone, the pressure at the entrance of the ear canal and the pressure at the second error microphone.

8. The noise reduction method of claim 7, further comprising:determining a loading impedance based on the pressure at the first error microphone, the pressure at the entrance of the ear canal, and the pressure at the second error microphone;obtaining the third ear canal length and the third attenuation coefficient based on the loading impedance; anddetermining the third transfer coefficient based on the third ear canal length and the third attenuation coefficient.

9. The noise reduction method of claim 8, further comprising:collecting a vibration signal via a reference microphone located between an inner space and an earphone cover;determining a pressure at the reference microphone based on the vibration signal collected by the reference microphone;determining whether a sealing between the human ear and an earphone meets requirements based on the loading impedance; anddetermining an ambient noise based on the pressure at the first error microphone, the pressure at the second error microphone, and the pressure at the reference microphone, whereinobtaining the third ear canal length and the third attenuation coefficient based on the loading impedance, comprises:obtaining the third ear canal length and the third attenuation coefficient based on the loading impedance in a case where the sealing between the human ear and the earphone meets the requirements and the ambient noise is less than or equal to a first threshold.

10. The noise reduction method of claim 9, further comprising:determining a new loading impedance based on a new vibration signal in a case where the sealing between the human ear and the earphone does not meet the requirements, and / or the ambient noise is greater than the first threshold; anddetermining a new transfer coefficient based on the new loading impedance, wherein determining the eardrum pressure based on the pressure at the entrance of the ear canal and the transfer coefficient, comprises:determining the eardrum pressure based on the pressure at the entrance of the ear canal and the new transfer coefficient.

11. The noise reduction method of claim 10, wherein determining the eardrum pressure based on the pressure at the entrance of the ear canal and the transfer coefficient, comprises:determining the eardrum pressure based on a first transfer coefficient or a second transfer coefficient in a case where the sealing between the human ear and the earphone does not meet the requirements, and / or in a case where the ambient noise is greater than the first threshold, whereinthe first transfer coefficient is determined based on a first ear canal length and a first attenuation coefficient, and the first ear canal length and the first attenuation coefficient are preset values, and the second transfer coefficient is determined based on a second ear canal length and a second attenuation coefficient, and the second ear canal length and the second attenuation coefficient are historical average values.

12. The noise reduction method of any of claims 7 to 11, wherein determining the eardrum pressure based on the pressure at the entrance of the ear canal and the transfer coefficient, comprises:determining the eardrum pressure based on the pressure at the entrance of the ear canal and the third transfer coefficient in a case where the value of the third transfer coefficient is usable.

13. The noise reduction method of claim 12, wherein determining the eardrum pressure based on the pressure at the entrance of the ear canal and the transfer coefficient, comprises:determining the eardrum pressure based on the pressure at the entrance of the ear canal and a fourth transfer coefficient in a case where the value of the third transfer coefficient is not usable, wherein the fourth transfer coefficient is the new transfer coefficient obtained based on the new vibration signal, a first transfer coefficient determined based on first ear canal length and first attenuation coefficient, or a second transfer coefficient determined based on the second ear canal length and the second attenuation coefficient, the first ear canal length and the first attenuation coefficient are preset values, and the second ear canal length and the second attenuation coefficient are historical average values.

14. A noise reduction earphone, comprising:an inner space, an earphone cover, a speaker, a second error microphone and an controller; wherein the speaker is disposed in the inner space of the earphone, the controller is disposed in the inner space of the earphone, the second error microphone disposed between the speaker and an earbud output port of the earphone; andthe second error microphone is configured to collect a vibration signal for sensing acoustic field outside the earbud output port, the controller is configured to determine a pressure at the second error microphone based on the vibration signal collected by the second error microphone, determine a pressure at an entrance of an ear canal based on the pressure at the second error microphone, determine an eardrum pressure based on a transfer coefficient and the pressure at the entrance of the ear canal, and determine a noise reductionsignal for reducing noise based on the eardrum pressure, the speaker is configured to play a noise reduction signal.

15. The noise reduction earphone of claim 14, further comprising:a protective tube disposed beside the earbud output port, and the second error microphone is disposed in the protective tube.

16. The noise reduction earphone of claim 14, wherein the second error microphone is disposed between the earbud output port and the earphone cover, and the second error microphone is protruding from the inner space.

17. The noise reduction earphone of any of claims 14 to 16, wherein the pressure at the entrance of the ear canal is equal to the pressure at the second error microphone; orthe pressure at the entrance of the ear canal is equal to a product of the pressure at the second error microphone and a first coefficient.

18. The noise reduction earphone of any of claims 14 to 16, further comprising:a first error microphone between the speaker and the earbud output port, wherein the first error microphone is configured to collect a vibration signal, andthe controller is further configured to:determine a pressure at the first error microphone based on the vibration signal collected by the first error microphone, whereindetermine the pressure at the entrance of the ear canal is further based on the pressure at the first error microphone.

19. The noise reduction earphone of claim 18, wherein the pressure at the entrance of the ear canal is equal to a sum of a product of the pressure at the first error microphone and a second coefficient and a product of the pressure at the second error microphone and a third coefficient.

20. The noise reduction earphone of any of claims 14 to 19, wherein the transfer coefficient is a first transfer coefficient, and the first transfer coefficient is determined based on a first ear canal length and a first attenuation coefficient that are preset values.

21. The noise reduction earphone of claims 14 to 19, wherein the transfer coefficient is a second transfer coefficient, and the second transfer coefficient is determined based on a second ear canal length and a second attenuation coefficient, and the second ear canal length and the second attenuation coefficient are historical average values.

22. The noise reduction earphone of claims 14 to 19, wherein the transfer coefficient is a third transfer coefficient, and the third transfer coefficient is determined based on a third ear canal length and a third attenuation coefficient, and the third ear canal length and the third attenuation coefficient are calculated based on the pressure at the first error microphone, the pressure at the entrance of the ear canal and the pressure at the second error microphone.

23. The noise reduction earphone of claim 22, the controller is further configured to:determine a loading impedance based on the pressure at the first error microphone, the pressure at the entrance of the ear canal, and the pressure at the second error microphone;obtain the third ear canal length and the third attenuation coefficient based on the loading impedance; anddetermine the third transfer coefficient based on the third ear canal length and the third attenuation coefficient.

24. The noise reduction earphone of claim 23, further comprising:a reference microphone located between the inner space and the earphone cover, wherein the reference microphone is configured to collect a vibration signal, andthe controller is further configured to:determine a pressure at the reference microphone based on the vibration signal at the reference microphone;determine whether a sealing between the human ear and an earphone meets requirements based on the loading impedance;determine an ambient noise based on the pressure at the first error microphone, the pressure at the second error microphone, and the pressure at the reference microphone; andobtain the third ear canal length and the third attenuation coefficient based on the loading impedance in a case where the sealing between the human ear and the earphone meets the requirements and the ambient noise is less than or equal to a first threshold.

25. The noise reduction earphone of claim 24, the controller is further configured to:determine a new loading impedance based on a new vibration signal in a case where the sealing between the human ear and the earphone does not meet the requirements, and / or the ambient noise is greater than the first threshold; anddetermine a new transfer coefficient based on the new loading impedance; anddetermine the eardrum pressure based on the pressure at the entrance of the ear canal and the new transfer coefficient.

26. The noise reduction earphone of claim 25, the controller is further configured to:determine the eardrum pressure based on a first transfer coefficient or a second transfer coefficient in acase where the sealing between the human ear and the earphone does not meet the requirements, and / or in a case where the ambient noise is greater than the first threshold, whereinthe first transfer coefficient is determined based on a first ear canal length and a first attenuation coefficient, and the first ear canal length and the first attenuation coefficient are preset values, and the second transfer coefficient is determined based on a second ear canal length and a second attenuation coefficient, and the second ear canal length and the second attenuation coefficient are historical average values.

27. The noise reduction earphone of claim 26, the controller is further configured to determine the eardrum pressure based on the pressure at the entrance of the ear canal and the third transfer coefficient in a case where the value of the third transfer coefficient is usable.

28. The noise reduction earphone of claim 27, the controller is further configured to:determine the eardrum pressure based on the pressure at the entrance of the ear canal and a fourth transfer coefficient in a case where the value of the third transfer coefficient is not usable, wherein the fourth transfer coefficient is the new transfer coefficient obtained based on the new vibration signal, a first transfer coefficient determined based on first ear canal length and first attenuation coefficient, or a second transfer coefficient determined based on the second ear canal length and the second attenuation coefficient, the first ear canal length and the first attenuation coefficient are preset values, and the second ear canal length and the second attenuation coefficient are historical average values.

29. A computer-readable storage medium having instructions stored thereon which, when executed by a noise reduction earphone, cause the noise reduction earphone to perform the methods of any one of claims 1 to 13.

30. A computer program product storing instructions which, when executed, cause a noise reduction earphone to perform the method of any one of claims 1 to 13.

Images