Active noise reduction method and active noise reduction headphones

Abstract

The present application provides an active noise reduction method and an active noise reduction headset, which relate to the field of audio noise reduction. The active noise reduction headset comprises: an active noise reduction channel; a first upsampling module; a speaker; the first upsampling module comprises a first upsampling unit; the first upsampling unit comprises a target configuration, the target configuration comprising: obtaining the sampling points of the intermediate audio signal, and inserting (M‑1) preset sampling points after each sampling point, where M is a preset upsampling multiple of the first upsampling unit, and M is a positive integer. The active noise reduction headset helps to reduce the output delay and power consumption of the audio signal during noise reduction.

Description

Technical Field

[0001] The present application relates to the field of audio noise reduction, and in particular, provides an active noise reduction method and an active noise reduction headset. Background Art

[0002] Active noise reduction headphones include an active noise reduction channel, which includes a microphone, an analog gain module, an analog-to-digital conversion module, a downsampling module, an active noise reduction filter, and an upsampling module. After the audio signal is collected by the microphone, it will be processed by the following modules and finally output the noise-reduced audio signal. However, there will be a certain delay in the processing of the audio signal by each module, and the total delay accumulated by each module is large, which affects the audio playback effect.

[0003] At the same time, the upsampling module will upsample the downsampled audio signal to restore the sampling rate of the audio signal. However, the upsampling module includes a low-pass filter. When upsampling, the upsampling module usually inserts a 0 value between two adjacent sampling points so that the number of sampling points matches the sampling rate. Inserting a 0 value will introduce high-frequency components, and the low-pass filter will generate a large delay and power consumption when filtering the sampling points containing 0 values. Summary of the invention

[0004] In view of this, the present application aims to provide an active noise reduction method and an active noise reduction headset to reduce the power consumption and delay of the active noise reduction headset when performing active noise reduction.

[0005] In a first aspect, an embodiment of the present application provides an active noise reduction headset, comprising: an active noise reduction channel, the active noise reduction channel comprising a downsampling module and an active noise reduction filter connected in sequence; an initial audio signal input into the active noise reduction channel is first downsampled by the downsampling module, and then actively noise reduced by the active noise reduction filter to obtain an intermediate audio signal; a first upsampling module, connected to the active noise reduction filter; a speaker, connected to the first upsampling module; the first upsampling module comprises a first upsampling unit, and the first upsampling unit is respectively connected to the active noise reduction filter and the speaker; the first upsampling unit comprises a target configuration, and the target configuration comprises: obtaining sampling points of the intermediate audio signal, and inserting (M-1) preset sampling points after each sampling point, where M is a preset upsampling multiple of the first upsampling unit, and M is a positive integer; the value of the preset sampling point is equal to the value of the previous sampling point.

[0006] During active noise reduction, the audio signal will be downsampled before noise reduction to reduce the power consumption of the active noise reduction filter, and the active noise reduction filter needs to restore the sampling rate of the audio signal through upsampling. The existing upsampling usually inserts a 0 value and then uses a low-pass filter to filter out the high-frequency components generated by the 0-value sampling point. Different from the existing upsampling, in the embodiment of the present application, the first upsampling module does not include a low-pass filter, and there is no need to use a low-pass filter for filtering, thereby reducing the delay and power consumption generated by filtering the upsampled audio signal. Furthermore, after each sampling point, a preset sampling point is inserted, and the preset sampling point has the same value as the previous sampling point, which can effectively reduce the insertion of the 0-value sampling point, thereby reducing the high-frequency noise component caused by the 0-value sampling point. Even if the low-pass filter is not set, the audio signal upsampled by the first upsampling module can be output and played normally. Since the power consumption and delay at the upsampling point are reduced, the overall delay and power consumption of the active noise reduction can be reduced, and the audio playback effect can be improved. In addition, since the value of the preset sampling point is equal to the value of the previous sampling point, on the one hand, there is no need to additionally calculate the value of the sampling point, and on the other hand, the low-pass filter performs noise reduction on the same sampling point, both of which can reduce the amount of calculation, reduce latency and power consumption.

[0007] In one embodiment, the active noise reduction channel includes: a feedforward active noise reduction channel and / or a feedback active noise reduction channel.

[0008] Active noise reduction is divided into feedforward active noise reduction and feedback active noise reduction. In the embodiment of the present application, the audio signals output by the active noise reduction channel and the feedback active noise reduction channel can both restore the sampling rate through the first upsampling module to reduce the power consumption and delay of the feedforward active noise reduction and / or feedback active noise reduction.

[0009] In one embodiment, the first up-sampling module includes a plurality of first up-sampling units; the plurality of first up-sampling units are connected in series; and at least one of the plurality of first up-sampling units includes the target configuration.

[0010] Some active noise reduction headphones are provided with multiple levels of first upsampling units to gradually increase the sampling rate of the audio signal through the multiple levels of first upsampling units. In the embodiment of the present application, in the case of multiple levels of first upsampling units, any group of first upsampling units with a target configuration can achieve a certain effect of reducing power consumption and delay. When all first upsampling units have the target configuration, a better effect of reducing power consumption and delay can be achieved.

[0011] In one embodiment, at least a first-stage first up-sampling unit connected to the active noise reduction filter among the multiple stages of the first up-sampling units includes the target configuration.

[0012] In the embodiment of the present application, the audio signal output by the first-level first upsampling unit will be used by each subsequent group of first upsampling units. Setting the target configuration in the first-level first upsampling unit can enable the subsequent first upsampling units in the subsequent first upsampling modules to perform subsequent upsampling processing on the audio signal including the preset sampling point. Therefore, compared with setting the first upsampling unit with the target configuration in each subsequent group of first upsampling units, setting the target configuration in the first-level first upsampling unit can achieve a better effect of reducing latency and power consumption.

[0013] In one embodiment, the active noise reduction headset also includes: a second upsampling module, the output end of the second upsampling module is connected to the input end of the speaker; the second upsampling module is used to input the audio signal to be played; the audio signals output by the first upsampling module and the second upsampling module are mixed and output.

[0014] In the embodiment of the present application, the high-frequency audio signal in the audio signal to be played can be filtered out by the second up-sampling module, thereby reducing the power consumption when playing the audio signal to be played.

[0015] In one embodiment, the active noise reduction headset further includes: a first low-pass filter, wherein the first low-pass filter is connected between the active noise reduction filter and the first upsampling module; the first low-pass filter is used to perform low-pass filtering on the audio signal output by the active noise reduction filter.

[0016] Before the audio signal is output to the first upsampling module, the active noise reduction channel will generate high-frequency noise. The audio signal output by the active noise reduction channel will be played after passing through the amplifier, speaker and other circuits to offset the noise signal. The high-frequency noise generated by the active noise reduction channel will increase the power consumption of the amplifier, speaker and other circuits in the active noise reduction headset. Therefore, in the embodiment of the present application, a first low-pass filter can be set in the active noise reduction headset to filter out the high-frequency noise generated by the active noise reduction channel through the first low-pass filter, thereby reducing the power consumption generated by the subsequent circuit processing it.

[0017] In one embodiment, a cut-off frequency of the first low-pass filter is greater than 20 KHz.

[0018] Normally, audio signals greater than 20KHz cannot be heard by human ears. Therefore, in the embodiment of the present application, even if the audio signals greater than 20KHz are filtered out by a low-pass filter, it will not affect the noise reduction effect of the active noise reduction. On the contrary, because the audio signals greater than 20KHz are filtered out, the power consumption generated by the subsequent amplifiers, speakers and other circuits in the active noise reduction headphones for processing the audio signals can be reduced.

[0019] In one embodiment, the first low-pass filter is a second-order IIR filter.

[0020] In one embodiment, the active noise reduction earphone is one of an in-ear earphone, a semi-in-ear earphone, an open earphone, and a true wireless stereo earphone.

[0021] In a second aspect, an embodiment of the present application provides an active noise reduction method, which is applied to the active noise reduction headphones as described in any one of the first aspects, and the active noise reduction method includes: obtaining an intermediate audio signal output after downsampling and active noise reduction through an active noise reduction channel; obtaining a sampling point of the intermediate audio signal based on a first upsampling module; inserting (M-1) preset sampling points after each sampling point based on the first upsampling module, where M is the ratio of a preset output sampling rate of the output audio signal of the first upsampling unit to an input sampling rate of the input audio signal of the first upsampling unit, and M is a positive integer. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 This is a first schematic diagram of an active noise reduction headset provided by an embodiment of the present application;

[0024] Figure 2 A second schematic diagram of an active noise reduction headset provided by an embodiment of the present application;

[0025] Figure 3 A schematic diagram of a downsampling submodule provided by an embodiment of the present application;

[0026] Figure 4 A connection diagram of a multi-stage first up-sampling unit provided in one embodiment of the present application;

[0027] Figure 5 The present invention provides a flowchart of an active noise reduction method according to an embodiment of the present invention.

[0028] Icon: active noise reduction headphones 10; active noise reduction channel 11; feedforward active noise reduction channel 1111; feedforward active noise reduction filter 1112; feedforward microphone 1113; feedback active noise reduction channel 1122; feedback active noise reduction filter 1122; feedback microphone 1123; first upsampling module 12; first upsampling unit 1211; speaker 13; analog gain module 141; analog-to-digital converter 142; downsampling module 143; downsampling low-pass filter 1431; downsampling unit 1432; digital-to-analog converter 144; limiter 145; audio echo module 15; second upsampling module 16. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the embodiments of the present application more clear, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0030] First, an embodiment of the present application provides an active noise reduction headset, and the active noise reduction headset 10 can be an in-ear headset, a semi-in-ear headset, an open-type headset, or a head-mounted headset, which is not limited here.

[0031] See also Figure 1 , Figure 1 The first schematic diagram of an active noise reduction headset 10 provided in an embodiment of the present application includes: an active noise reduction channel 11, a first upsampling module 12 and a speaker 13. The active noise reduction channel 11 includes a downsampling module 143 and an active noise reduction filter connected in sequence, the first upsampling module 12 is connected to the active noise reduction filter, and the speaker 13 is connected to the first upsampling module 12.

[0032] The active noise reduction channel 11 is used to collect and process ambient sound, so as to actively reduce the noise of the sound played by the speaker 13 through the processed ambient sound.

[0033] In an embodiment of the present application, the active noise reduction channel 11 includes a microphone, a downsampling module 143 and an active noise reduction filter. The microphone is used to collect audio signals, which are used for noise reduction after being processed by the active noise reduction filter. Before being processed by the active noise reduction filter, the audio signal is first downsampled by the downsampling module 143 to reduce the sampling rate of the audio signal, thereby reducing the amount of calculation of the active noise reduction filter.

[0034] That is, in the active noise reduction channel 11, the ambient sound is used as the initial audio signal, and the initial audio signal input into the active noise reduction channel 11 is first down-sampled by the down-sampling module 143, and then actively noise-reduced by the active noise reduction filter to obtain an intermediate audio signal.

[0035] See also Figure 2 , Figure 2 This is a second schematic diagram of an active noise reduction headset 10 provided in an embodiment of the present application. In the embodiment of the present application, the active noise reduction channel 11 may include at least one of a feedforward active noise reduction channel 111 and a feedback active noise reduction channel 112. The feedforward active noise reduction channel 111 and the feedback active noise reduction channel 112 may work separately or together.

[0036] The feedforward active noise reduction channel 111 includes a feedforward microphone 1113, an analog gain module 141, an analog-to-digital converter 142, a downsampling module 143, and a feedforward active noise reduction filter 1112 connected in sequence. The audio signal collected by the feedforward microphone 1113 passes through the feedforward microphone 1113, the analog gain unit, the analog-to-digital converter 142, the downsampling module 143, and the feedforward active noise reduction filter 1112 in sequence, and is output to the digital-to-analog converter 144, which converts the audio signal into an analog signal and then outputs it to the speaker 13 for playback.

[0037] Among them, the microphone of the feedforward active noise reduction channel 111 is placed on the outside of the earphone to collect sounds outside the ear, so it can also be called an external ear microphone. The feedforward microphone 1113 can be composed of multiple microphones, and the audio signal collected by the feedforward microphone 1113 can be beamformed first, and then passed through the feedforward active noise reduction filter 1112 to reduce noise. In other embodiments, the feedforward microphone 1113 can also be a separately set microphone, which is not limited here.

[0038] like Figure 2 As shown, the feedback active noise reduction channel 112 includes a feedback microphone 1123, an analog gain unit, an analog-to-digital converter 142, a downsampling module 143 and a feedback active noise reduction filter 1122 connected in sequence. The audio signal collected by the feedback microphone 1123 passes through the feedback microphone 1123, the analog gain unit, the analog-to-digital converter 142, the downsampling module 143, and the feedback active noise reduction filter 1122 in sequence, and is output to the digital-to-analog converter 144, and is converted by the digital-to-analog converter 144 into an analog signal and then output to the speaker 13 for playback. The feedback microphone 1123 of the feedback active noise reduction channel 112 is placed on the inside of the earphone, close to the ear canal when worn, and is used to collect the sound in the ear, so as to perform feedback noise reduction based on the sound collected in the ear. Therefore, the feedback microphone 1123 can also be called an in-ear microphone. In some embodiments, the in-ear microphone can also be a separately arranged microphone or a microphone array.

[0039] In addition, the active noise reduction headset 10 may also include an audio echo module 15. In the active noise reduction headset 10, when playing audio, the audio to be played can be output to the digital-to-analog converter 144 for conversion and played by the speaker 13140. On the other hand, when the feedback active noise reduction channel 112 is turned on, the audio signal to be played passes through the audio echo module 15 to offset the audio component to be played in the audio signal processed in the feedback active noise reduction channel 112, so that the sound collected in the feedback active noise reduction channel 112 is not affected by the audio to be played. Specifically, the audio signal to be played is added or subtracted from the output of the audio echo module 15 and the output of the downsampling module in the feedback active noise reduction channel 112. After eliminating the influence of the audio to be played on the feedback active noise reduction channel 112, the remaining environmental noise is sent to the feedback active noise reduction filter 1122 as the input of the digital-to-analog converter 144.

[0040] In the embodiment of the present application, the feedforward active noise reduction filter 1112 and the feedback active noise reduction filter 1122 can be adaptive filters or fixed filters. Both can be IIR (Infinite Impulse Response, infinite impulse response filter) structure, FIR (Finite Impulse Response, finite impulse response filter) structure, or a filter structure mixed with IIR and FIR.

[0041] The analog gain module 141 , the analog-to-digital converter 142 , and the down-sampling module 143 of the feedback active noise reduction channel 112 and the feedforward active noise reduction channel 111 respectively play the same role, and their structures may be the same or different.

[0042] In some embodiments, the feedback active noise reduction channel 112 may also be provided with a limiter 145, and the limiter 145 is connected between the feedback active noise reduction filter 1122 and the digital-to-analog converter 144. In other embodiments, the limiter 145 may not be provided, which is not limited here.

[0043] In an embodiment of the present application, the feedforward microphone 1113 and / or the feedback microphone 1123 may be an analog microphone to collect audio signals in the form of analog signals. In other embodiments, the feedforward microphone 1113 and / or the feedback microphone 1123 may also be a digital microphone. Accordingly, if the feedforward microphone 1113 and / or the feedback microphone 1123 are digital microphones, the corresponding active noise reduction channel 11 may not include an analog-to-digital conversion module and an analog gain module 141. Other structures and functions of the active noise reduction headset 10 that are not described in the above content may refer to the prior art and will not be expanded here.

[0044] See also Figure 3 , Figure 3 A schematic diagram of a downsampling submodule provided for an embodiment of the present application. In an embodiment of the present application, the downsampling module 143 includes one or more stages of downsampling submodules connected in series, each stage of the downsampling submodule includes a downsampling low-pass filter 1431 and a downsampling unit 1432, and the input downsampling submodule first filters out part of the noise component through the downsampling low-pass filter 1431 to avoid spectrum aliasing after downsampling, and the cutoff frequency of the downsampling low-pass filter 1431 is related to the downsampling multiple N. The downsampling low-pass filter 1431 can be composed of a multi-stage CIC (Cascaded Integrator-Comb Filter, integral comb filter) filter.

[0045] The down sampling unit 1432 is used to reduce the sampling rate of the input audio signal to 1 / N of the original sampling rate, where N is a positive integer, and can be 2, 3, 4, 6, 8, 12, 16, etc. For example, when N=8, the sampling rate of the input audio signal is 6.144MHz, and the sampling rate of the output audio signal of the down sampling unit 1432 is 768KHz. Similarly, when the sampling rate of the input audio signal is 3.072MHz, the sampling rate of the output audio signal is 384KHz.

[0046] When multiple downsampling submodules are connected, the product of the downsampling multiples of the N-fold downsampling units 1432 in the multiple downsampling submodules, for example, the downsampling module 143 includes three groups of downsampling submodules, and the downsampling multiples of the downsampling units 1432 in the three groups of downsampling submodules are N1, N2, and N3 respectively, then the total downsampling multiple of the downsampling module 143 is N1*N2*N3. The relevant contents of the above-mentioned downsampling module 143 can refer to the prior art and will not be expanded here.

[0047] The downsampling module 143 is used to reduce the sampling rate of the audio signal to reduce the amount of calculation of the active noise reduction filter on the audio signal processing, thereby reducing the delay and power consumption. In order to play the audio signal correctly so that it can be used to cancel the noise, it is also necessary to upsample the intermediate audio signal output by the active noise reduction filter to restore its sampling rate.

[0048] In the embodiment of the present application, a first upsampling module 12 is further provided after the active noise reduction filter, so as to upsample the audio signal after the active noise reduction through the first upsampling module 12 to restore the sampling rate of the audio signal reduced by downsampling.

[0049] The existing upsampling module includes a zero insertion module and a low-pass filter. The zero insertion module is used to insert a 0 value between two sampling points of the audio signal to restore the sampling rate of the audio signal. The number of 0 values ​​is related to the upsampling multiple. For example, if the upsampling multiple is M, M-1 0 values ​​are inserted between each sampling point. The low-pass filter is used to perform low-pass filtering on the audio signal after zero insertion to remove the high-frequency components introduced by zero insertion and restore a smooth signal.

[0050] The first up-sampling module 12 provided in the embodiment of the present application includes a first up-sampling unit 1211 , and the first up-sampling unit 1211 is connected to the active noise reduction filter and the speaker 13 respectively.

[0051] First, unlike the existing upsampling modules, the first upsampling module 12 provided in the present application does not include a low-pass filter, and there is no need to perform low-pass filtering on the sampling points after the first upsampling module performs upsampling. Thus, the time delay and power consumption of upsampling the output audio signal can be effectively reduced.

[0052] Next, the first up-sampling unit 1211 is different from the zero insertion module in the existing up-sampling module. In the embodiment of the present application, the first up-sampling unit 1211 includes a target configuration, which includes: obtaining the sampling points of the intermediate audio signal, and inserting (M-1) preset sampling points after each sampling point, where M is the preset up-sampling multiple of the first up-sampling unit 1211. And M is a positive integer, and the value of M is equal to the ratio of the preset output sampling rate of the output audio signal of the first up-sampling unit 1211 to the input sampling rate of the input audio signal of the first up-sampling unit 1211, and M is a positive integer. Among them, the value of the preset sampling point is equal to the value of the previous sampling point at the inserted position.

[0053] That is, in an embodiment of the present application, the sampling rate of the audio signal is restored by inserting a preset sampling point, and the value of the preset sampling point is equal to the value of the previous sampling point at the inserted position. Generally, the value of the sampling point is usually not 0. Therefore, when inserting the preset sampling point, most of the inserted preset sampling points are non-zero values. Compared with inserting a zero value, on the one hand, since the preset sampling point is equal to the value of the previous sampling point, the preset sampling point can make the processed audio signal smoother. On the other hand, the preset sampling point is mostly non-zero value, which can reduce the introduction of high-frequency noise components by upsampling. Therefore, even if the low-pass filter is not configured subsequently, the audio signal output by the first upsampling module can be used normally.

[0054] For example, assuming that three consecutive sampling points of the audio signal are a1, a2, and a3, and the upsampling multiple is 3, in this embodiment, the upsampling results of the first upsampling unit 1211 are a1, a1, a1, a2, a2, a2, a3, a3, and a3.

[0055] In this embodiment, on the one hand, there is no need to additionally calculate the preset sampling points, and on the other hand, the low-pass filter processes the same sampling points, both of which can reduce the amount of calculation, delay and power consumption.

[0056] In some embodiments of the present application, the first up-sampling module 12 may include a multi-stage first up-sampling unit 1211. Figure 4 , Figure 4 A connection diagram of a multi-stage first upsampling unit 1211 provided in an embodiment of the present application, in the first upsampling module, the first upsampling units are connected in series, the first first upsampling unit 1211 (or referred to as the first-stage first upsampling unit) is connected to an active noise reduction filter (such as a feedforward active noise reduction filter 1112 and a feedback active noise reduction filter 1122), and the last first upsampling unit 1211 is connected to the speaker 13 through a digital-to-analog conversion module.

[0057] In this embodiment, the final total upsampling multiple of the first upsampling module 12 is equal to the product of the upsampling multiples of all the first upsampling units 1211. For example, the first upsampling module 12 includes three levels of first upsampling units 1211, and the upsampling multiples of the three levels of first upsampling units 1211 are M1, M2 and M3 respectively, and the total upsampling multiple is M, M=M1*M2*M3.

[0058] In the multi-stage first up-sampling units 1211 connected in series, after each first up-sampling unit 1211 inserts a preset non-zero up-sampling point, the number of sampling points increases stage by stage. For example, two stages of first up-sampling units 1211 are connected in series. If the up-sampling multiple of each stage of the first up-sampling unit 1211 is 2, the value of the preset sampling point is equal to the value of the previous sampling point, and the sampling points input into the first up-sampling unit 1211 are b1, b2, and b3, then after passing through the first stage of the first up-sampling unit 1211, the sampling points become b1, b1, b2, b2, b3, and b3; after passing through the second stage of the first up-sampling unit 1211, the sampling points become b1, b1, b1, b1, b2, b2, b2, b3, b3, b3, and b3.

[0059] In an embodiment of the present application, part of the first up-sampling unit 1211 may be inserted into a non-zero preset sampling point, and another part of the up-sampling unit may be set to insert a 0-value sampling point. When a sampling point of 0 needs to be inserted, a low-pass filter may be set after the up-sampling module that inserts the 0-value sampling point to filter out the high-frequency noise introduced by the insertion of the 0-value sampling point. It should be noted that even if a low-pass filter is introduced, since some of the inserted sampling points are 0, compared with inserting all 0-value sampling points, the power consumption and delay will still be lower.

[0060] For example, when the first-stage first upsampling unit 1211 is the target configuration, the second-stage upsampling is to insert a 0 value, and the upsampling results of the two-stage first upsampling units 1211 of the preset sampling point will have some non-zero sampling points, and even if filtered by a low-pass filter, the power consumption and delay generated will be small. For another example, the first stage inserts a 0-value sampling point, and the second stage inserts a preset sampling point. Similarly, the sampling points obtained by the second-stage first upsampling unit 1211 are not all inserted with 0, but have some non-zero sampling points. Compared with inserting all 0-value sampling points, the power consumption and delay required for these non-zero sampling points to pass through the low-pass filter are lower.

[0061] Therefore, in the embodiment of the present application, at least one first up-sampling unit 1211 in the multi-stage first up-sampling unit 1211 may include a target configuration.

[0062] As mentioned above, the audio signal output by the first-stage first upsampling unit 1211 will continue to pass through the subsequent first upsampling units 1211 at various stages. Therefore, in some embodiments, at least the first-stage first upsampling unit 1211 connected to the active noise reduction filter among the multiple stages of first upsampling units 1211 may include a target configuration to reduce the power consumption generated by the audio signal output by the first-stage first upsampling unit 1211 in the subsequent-stage first upsampling unit 1211.

[0063] In the embodiment of the present application, all first up-sampling units 1211 may also include the target configuration. When all first up-sampling units 1211 include the target configuration, the effect of reducing power consumption and delay will be maximized.

[0064] Regardless of the feedforward active noise reduction channel 111 or the feedback active noise reduction channel 112, the audio signal outputted by the speaker 13 is played as an anti-noise signal to offset the ambient sound in the ear, thereby achieving the purpose of noise reduction. This requires that the delay of the audio signal outputted by the feedforward active noise reduction channel 111 and the feedback active noise reduction channel 112 be as low as possible to accurately offset the ambient noise in the ear and achieve a better noise reduction effect. The above-mentioned first sampling module can reduce the delay generated in the upsampling stage, thereby achieving the purpose of reducing the delay required for the entire active noise reduction process.

[0065] As mentioned above, the active noise reduction channel 11 includes at least one of the feedforward active noise reduction channel 111 and the feedback active noise reduction channel 112. Regardless of the feedforward active noise reduction channel 111 or the feedback active noise reduction channel 112, both have a downsampling module 143 and an active noise reduction filter inside, and both need to restore the sampling rate of the audio signal. Therefore, in an embodiment of the present application, the first upsampling module 12 can be connected to the feedforward active noise reduction channel 111 and the feedback active noise reduction channel 112 at the same time to reduce power consumption and delay when using different noise reduction methods (feedforward active noise reduction and / or feedback active noise reduction) for active noise reduction.

[0066] like Figure 2 As shown, in some embodiments of the present application, the active noise reduction headset 10 also includes: a second upsampling module 16, the output end of the second upsampling module 16 is connected to the input end of the speaker 13, the second upsampling module 16 is used to input the audio signal to be played, and the audio signals output by the first upsampling module and the second upsampling module are mixed and output. Among them, the second upsampling module 16 can be connected to the input end of the speaker 13 through a digital-to-analog converter 144. Among them, the audio signal to be played may be an audio signal such as music, voice, etc. In some embodiments, a third upsampling module is also provided before the digital-to-analog converter 144, and the audio signal mixed and output by the first upsampling module and the second upsampling module can be output by the speaker 13 after passing through the third upsampling module and the digital-to-analog converter 144 in sequence.

[0067] In an embodiment of the present application, the anti-aliasing performance of the second up-sampling module 16 is greater than that of the first up-sampling module 12, and its delay can be greater than that of the first up-sampling module 12. Among them, the audio signal to be played can be a sound source (music) signal, and the sampling rate of the sound source (music) signal is less than the sampling rate of the output signal of the first up-sampling module, so it is necessary to use the second up-sampling module 16 to up-sample the audio signal to be played. The playback of the audio signal to be played has low requirements for delay, or even high delay requirements, so the second up-sampling module 16 can be configured to have a stronger filtering capability for the high-frequency band, so that its anti-aliasing performance is better.

[0068] The second upsampling module 16 can work alone or together with the first upsampling module 12. When the second upsampling module 16 works together with the first upsampling module 12, the audio signals of the second upsampling module 16 and the first upsampling module 12 can be mixed (such as adding operation).

[0069] The second up-sampling module 16 may include a low-pass filter. When the second up-sampling module 16 works alone, the second up-sampling module 16 may perform a low-pass filter on the audio signal to be played to filter out high-frequency audio signals in the audio signal to be played, thereby reducing power consumption of subsequent circuits (such as amplifier circuits, speakers 13, etc.).

[0070] In this embodiment, in the music playback scenario, the delay requirement for noise reduction is relatively low, and the active noise reduction function may even be turned off. In such a scenario, in order to improve the filtering effect of high-frequency audio components and reduce the power consumption of the speaker 13, the second upsampling module 16 can be used to filter the audio signal to be played, thereby reducing the power consumption of the audio signal to be played.

[0071] In one embodiment of the present application, the active noise reduction headset 10 further includes: a first low-pass filter, the first low-pass filter is connected between the active noise reduction filter and the first upsampling module 12 ( Figure 2 not shown).

[0072] In the embodiment of the present application, the first low-pass filter may be a second-order IIR filter or a filter of other structures.

[0073] like Figure 2 As shown, the audio signal collected by the microphone will pass through the analog-to-digital converter 142 and the active noise reduction filter. The analog-to-digital converter 142 will also introduce noise when performing analog-to-digital conversion. For example, in the analog-to-digital conversion of existing audio signals, the analog-to-digital converter 142 used is a sigma-delta (a type of analog-to-digital converter 142) analog-to-digital converter 142. The analog-to-digital converter 142 has a large high-frequency noise. The sigma-delta analog-to-digital converter 142 is noise-shaped, and the quantization noise is pushed to the high frequency band. For digital microphones, pulse density modulation is generally used, and the quantization noise is also pushed to the high frequency band through noise shaping. Therefore, the analog-to-digital conversion will increase the high-frequency noise, which in turn makes the subsequent amplifier circuit and the speaker 13 consume more power in processing it.

[0074] Since the first up-sampling module 12 is not provided with a low-pass filter, it cannot process audio signals with narrower bandwidth and larger out-of-band attenuation, and cannot filter out the high-frequency noise introduced by the analog-to-digital converter 142. Therefore, in an embodiment of the present application, a first low-pass filter 1212 can be configured before the first up-sampling module 12 to filter out part of the high-frequency noise, thereby reducing the power consumption of subsequent circuits.

[0075] High-frequency noise above 20 KHz does not affect the hearing of human ears, but such high-frequency noise will increase the power consumption of the amplifier and the speaker 13. Therefore, in some embodiments of the present application, the cut-off frequency of the first low-pass filter is greater than 20 KHz.

[0076] Audio signals greater than 20KHz are usually inaudible to human ears, so even if the audio signals greater than 20KHz are filtered out, the noise reduction effect achieved by the output audio signals will not be affected, and since the audio signals greater than 20KHz are filtered out, the power consumption of the subsequent speaker 13 can be reduced. At the same time, the audio signal played by the speaker 13 is amplified by the amplifier circuit, and filtering the audio signals greater than 20KHz can also reduce the power consumption of the amplifier circuit.

[0077] At the same time, a low-pass filter with a high cutoff frequency also has a low delay. Therefore, the first low-pass filter has a lower delay. Since the frequency range of the audio signal that needs to be processed by the subsequent circuit is reduced, the delay in audio signal processing is reduced. Overall, setting the first low-pass filter will further reduce the delay.

[0078] Based on the same inventive concept, the present application embodiment provides an active noise reduction method, which can be applied to the active noise reduction headphones provided in any of the above embodiments. Figure 5 , Figure 5 An active noise reduction method is provided in an embodiment of the present application, and the active noise reduction method includes:

[0079] S510, obtaining an intermediate audio signal output after downsampling and active noise reduction through an active noise reduction channel.

[0080] S520: Acquire sampling points of the intermediate audio signal based on a first up-sampling module.

[0081] S530: insert (M-1) preset sampling points after each sampling point based on the first up-sampling module.

[0082] Wherein, M is the ratio of the preset output sampling rate of the output audio signal of the first upsampling unit to the input sampling rate of the input audio signal of the first upsampling unit, and M is a positive integer preset sampling point, and the value of the preset sampling point is equal to the value of the previous sampling point at the inserted position.

[0083] In one embodiment, the first upsampling module includes multiple levels of first upsampling units, and the multiple levels of first upsampling units are connected in series. The active noise reduction method also includes: inserting (m-1) preset sampling points after each sampling point of at least one level of first upsampling unit, where m is the upsampling multiple of the first upsampling unit, that is, m is the ratio of the preset output sampling rate of the output audio signal of the first upsampling unit in the first upsampling unit to the input sampling rate of the input audio signal of the first upsampling unit.

[0084] In one embodiment, the active noise reduction headset further includes: a second upsampling module, the output end of the second upsampling module is connected to the input end of the speaker; the active noise reduction method further includes: inputting the audio signal to be played based on the second upsampling module; and / or, the second upsampling module and the first upsampling module are mixed and then the audio signal is output.

[0085] In one embodiment, the active noise reduction headset further includes: a first low-pass filter connected between the active noise reduction filter and the first upsampling module. The active noise reduction method further includes: low-pass filtering the audio signal output by the active noise reduction filter based on the first low-pass filter.

[0086] In one embodiment, a cut-off frequency of the first low-pass filter is greater than 20 KHz.

[0087] It can be understood that the above active noise reduction method has the same function as that achieved by the aforementioned active noise reduction headphones. For details, please refer to the aforementioned active noise reduction headphones, which will not be elaborated here.

[0088] The above embodiments can be freely combined without conflict, and the embodiments obtained by the combination are included in the protection scope of this application.

[0089] The above detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0090] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0091] In the description of this application, it is also necessary to explain that, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0092] The above description is only an embodiment of the present application and is not intended to limit the protection scope of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An active noise reduction headset, characterized in that: include: An active noise reduction channel, the active noise reduction channel comprising a downsampling module and an active noise reduction filter connected in sequence; The initial audio signal input into the active noise reduction channel is first down-sampled by the down-sampling module, and then filtered by the active noise reduction filter to obtain an intermediate audio signal; A first up-sampling module connected to the active noise reduction filter; A speaker connected to the first upsampling module; The first upsampling module includes a first upsampling unit, and the first upsampling unit is connected to the active noise reduction filter and the speaker respectively; The first up-sampling unit includes a target configuration, wherein the target configuration includes: obtaining sampling points of the intermediate audio signal, and inserting (M-1) preset sampling points after each sampling point, where M is a preset up-sampling multiple of the first up-sampling unit, and M is a positive integer; The value of the preset sampling point is equal to the value of the previous sampling point at the inserted position.

2. The active noise reduction headset according to claim 1, characterized in that: The active noise reduction channel includes: a feedforward active noise reduction channel and / or a feedback active noise reduction channel.

3. The active noise reduction headset according to claim 1, characterized in that: The first up-sampling module includes a plurality of stages of first up-sampling units; Multiple stages of the first up-sampling units are connected in series; At least one of the multiple stages of the first up-sampling units includes the target configuration.

4. The active noise reduction headset according to claim 3, characterized in that: At least a first-stage first up-sampling unit connected to the active noise reduction filter among the multiple stages of the first up-sampling units includes the target configuration.

5. The active noise reduction headset according to claim 1, characterized in that: The active noise reduction headset further includes: a second upsampling module, wherein an output end of the second upsampling module is connected to an input end of the speaker; The second up-sampling module is used to input the audio signal to be played; The audio signals respectively output by the first up-sampling module and the second up-sampling module are mixed and then output.

6. The active noise reduction headset according to any one of claims 1 to 5, characterized in that: The active noise reduction headset further includes: a first low-pass filter, wherein the first low-pass filter is connected between the active noise reduction filter and the first up-sampling module; The first low-pass filter is used to perform low-pass filtering on the audio signal output by the active noise reduction filter.

7. The active noise reduction headset according to claim 6, characterized in that: The cut-off frequency of the first low-pass filter is greater than 20 KHz.

8. The active noise reduction headset according to claim 7, characterized in that: The first low-pass filter is a second-order IIR filter.

9. The active noise reduction headset according to claim 1, characterized in that: The active noise reduction earphone is one of an in-ear earphone, a semi-in-ear earphone, an open earphone, and a true wireless stereo earphone.

10. An active noise reduction method, characterized in that: Applied to the active noise reduction headset according to any one of claims 1 to 9, the active noise reduction method comprises: Obtaining an intermediate audio signal output after downsampling and active noise reduction through an active noise reduction channel; Acquire sampling points of the intermediate audio signal based on the first up-sampling module; Based on the first up-sampling module, (M-1) preset sampling points are inserted after each sampling point, where M is a ratio of a preset output sampling rate of an output audio signal of the first up-sampling unit to an input sampling rate of an input audio signal of the first up-sampling unit, and M is a positive integer, and a value of the preset sampling point is equal to a value of a previous sampling point at the inserted position.

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