CN111009254B - Audio echo filtering system and active noise reduction system - Google Patents
Audio echo filtering system and active noise reduction system Download PDFInfo
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Abstract
The embodiment of the application provides an audio echo filtering system and an active noise reduction system, and the audio echo filtering system comprises: an echo filtering component and an up-sampling filter; the echo filtering component is used for acquiring an audio signal to be broadcast in the active noise reduction earphone at a first sampling rate and filtering the audio signal to be broadcast; the up-sampling filter is used for outputting the audio signal to be broadcast which is filtered by the echo filtering component at a second sampling rate, and the second sampling rate is greater than the first sampling rate; and the audio signal to be broadcast output by the up-sampling filter at the second sampling rate is superposed with the audio echo signal output by the feedback noise reduction channel in the active noise reduction earphone at the second sampling rate so as to eliminate the audio echo signal in the feedback noise reduction channel. The method and the device can effectively reduce the sampling rate of the audio echo filtering while reducing the influence of the noise reduction channel on the playing of music.
Description
Technical Field
The application relates to the technical field of active noise reduction, in particular to an audio echo filtering system and an active noise reduction system.
Background
The active noise reduction earphone gradually walks to the life of people, so that people can obtain a relatively quiet environment in a noisy environment. The principle is to reduce the noise heard by the ear by actively emitting sound waves of opposite phase to cancel the sound waves (feed forward) or adding a feedback acoustic path to the sound path (feedback).
At present, both the noise reduction in a feedforward mode and the noise reduction in a feedback mode have an influence on played music, and the active noise reduction process in the feedback noise reduction mode has a particularly obvious influence on the played music. For example, in the existing active noise reduction scheme, the influence of active noise reduction on music can be reduced by the equalizer EQ.
However, the current feedback noise reduction method may cause the volume of the played sound to be reduced as a whole, and it is difficult to better eliminate the influence of noise reduction on music while controlling the hardware overhead.
Disclosure of Invention
To solve the problems in the prior art, the application provides an audio echo filtering system and an active noise reduction system, which can effectively reduce the sampling rate of audio echo filtering while reducing the influence of a noise reduction channel on playing music.
In order to solve the technical problem, the application provides the following technical scheme:
In a first aspect, the present application provides an audio echo filtering system, comprising: an echo filtering component and an up-sampling filter;
the echo filtering component is used for acquiring an audio signal to be broadcasted in the active noise reduction earphone at a first sampling rate and filtering the audio signal to be broadcasted;
the up-sampling filter is used for outputting the audio signal to be broadcasted after being filtered by the echo filtering component at a second sampling rate, and the second sampling rate is greater than the first sampling rate;
and the audio signal to be broadcasted output by the up-sampling filter at the second sampling rate is superposed with the audio echo signal output by the feedback noise reduction passage in the active noise reduction earphone at the second sampling rate so as to eliminate the audio echo signal in the feedback noise reduction passage.
Further, the echo filtering component comprises: a first down-sampling filter and a first echo filter connected to each other;
the first down-sampling filter is used for acquiring the audio signal to be broadcasted at the first sampling rate and sending the audio signal to be broadcasted to the first echo filter for filtering.
Further, the up-sampling filter is connected with the first echo filter;
The up-sampling filter is used for outputting the audio signal to be broadcasted which is output after being processed by the first echo filter at the second sampling rate.
Further, the system also comprises a filter coefficient self-adaptive adjusting module;
the filtering coefficient self-adaptive adjusting module comprises a second down-sampling filter, a self-adaptive echo filter and a third down-sampling filter;
the second downsampling filter is used for acquiring an audio signal to be broadcasted in the active noise reduction earphone at a first sampling rate, filtering the audio signal to be broadcasted and outputting the filtered audio signal to the adaptive filter;
the third down-sampling filter is connected with a fourth down-sampling filter in the feedback noise reduction path and used for acquiring an audio echo signal output by the fourth down-sampling filter at the first sampling rate, and superposing the audio echo signal and an audio signal to be broadcasted output by the adaptive filter to generate an error signal for controlling the adaptive echo filter to adaptively update a filter coefficient;
and a first echo filter in the echo filtering component carries out filtering processing on the audio data to be broadcasted according to the filtering coefficient adjusted by the self-adaptive echo filter.
Further, the system also comprises a reading time adjusting module;
the second downsampling filter reads the audio data to be broadcasted at the time t 1;
the reading time adjusting module is an advanced reading module, is connected to the first downsampling filter, and is configured to control the first downsampling filter to read the audio data to be broadcasted at time t 2;
wherein time t2 is earlier than the time t 1.
Further, the system also comprises a reading time adjusting module;
the first downsampling filter reads the audio data to be broadcasted at the time t 2;
the reading time adjusting module is a delay reading module, is connected to the second downsampling filter, and is configured to control the second downsampling filter to read the audio data to be broadcasted at time t 1;
wherein time t2 is earlier than the time t 1.
Further, the time difference between the time t1 and the time t2 is equal to the sum of the time delays of the first echo filter, the second downsampling filter, and the upsampling filter.
Further, the second sampling rate is an integer multiple of the first sampling rate.
In a second aspect, the present application provides an active noise reduction system, comprising: a feedback noise reduction path and an audio echo filtering system for canceling an audio echo signal in the feedback noise reduction path;
Wherein the audio echo filtering system comprises an echo filtering component and an up-sampling filter;
the echo filtering component is used for acquiring an audio signal to be broadcasted in the active noise reduction earphone at a first sampling rate and filtering the audio signal to be broadcasted;
the up-sampling filter is used for outputting the audio signal to be broadcasted after being filtered by the echo filtering component at a second sampling rate, and the second sampling rate is greater than the first sampling rate;
and the audio signal to be broadcasted output by the up-sampling filter at the second sampling rate is superposed with the audio echo signal output by the feedback noise reduction channel at the second sampling rate so as to eliminate the audio echo signal in the feedback noise reduction channel.
Further, still include: a time delay unit;
the time delay unit is connected to a digital-to-analog converter in the active noise reduction earphone and is used for outputting the audio signal to be broadcast in the active noise reduction earphone in a time delay manner, so that the audio signal to be broadcast output in a time delay manner is superposed with the internal noise signal which is output by the feedback noise reduction channel and is subjected to audio echo elimination and filtering, and then the internal noise signal is output to the digital-to-analog converter in the active noise reduction earphone.
Further, comprising: a feed-forward noise reduction path;
the feedforward noise reduction path is connected to a digital-to-analog converter in the active noise reduction earphone and used for collecting an external noise signal of the active noise reduction earphone and filtering the external noise signal.
Further, the feed-forward noise reduction path includes: the feedforward microphone, the first analog-to-digital converter, the feedforward downsampling filter and the feedforward filter are sequentially connected and are used for collecting the external noise signal;
the feedforward filter is connected with the digital-to-analog converter.
Further, the feed-forward noise reduction path further comprises: a first analog gain unit;
the first analog gain unit is used for amplifying the external noise signal collected by the feedforward microphone and outputting the amplified signal to the first analog-to-digital converter.
Further, the feedback noise reduction path includes: the feedback microphone, the second analog-to-digital converter, the fourth down-sampling filter and the feedback filter are sequentially connected and are used for collecting the internal noise signal and the audio echo signal of the active noise reduction earphone;
the feedback filter is connected with a digital-to-analog converter in the active noise reduction earphone.
Further, the feedback noise reduction path further comprises: a second analog gain unit;
the second analog gain unit is used for amplifying the internal noise signal collected by the feedback microphone and outputting the amplified signal to the second analog-to-digital converter.
According to the technical scheme, the audio echo filter system and the active noise reduction system can eliminate the audio echo signal in the feedback noise reduction channel, can reduce the influence on music from the noise reduction channel, fundamentally solves the influence on music caused by active noise reduction, reduces the original-taste sound cavity, and can work at a lower sampling rate, reduce the hardware (such as storage) overhead, greatly reduce the operation complexity, further effectively reduce the influence on playing music caused by the noise reduction channel, effectively reduce the sampling rate of the audio echo filter, and effectively reduce the hardware overhead and the operation complexity.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of an audio echo filtering system according to an embodiment of the present application;
FIG. 2 is a diagram illustrating the relationship of components of an echo filtering component of an audio echo filtering system according to an embodiment of the present application;
FIG. 3 is a schematic diagram illustrating a connection relationship between an upsampling filter and a first echo filter in an audio echo filtering system according to an embodiment of the present application;
fig. 4 is a schematic structural diagram of an audio echo filtering system including a filter coefficient adaptive adjustment module according to an embodiment of the present application;
fig. 5 is a schematic structural diagram of an audio echo filtering system including a first implementation manner of a read time adjustment module in an embodiment of the present application;
fig. 6 is a schematic structural diagram of an audio echo filtering system according to a second implementation manner including a reading time adjustment module in an embodiment of the present application;
FIG. 7 is a schematic structural diagram of an active noise reduction system in an embodiment of the present application;
fig. 8 is a detailed structural diagram of the active noise reduction system in the embodiment of the present application.
Reference numerals:
1. an audio echo filtering system;
11. an echo filtering component;
111. a first down-sampling filter;
112. a first echo filter;
12. an upsampling filter;
13. a filtering coefficient self-adaptive adjusting module;
131. A second downsampling filter;
132. an adaptive echo filter;
133. a third downsampling filter;
14. a reading time adjusting module;
141. an advanced reading module;
142. a delayed read module;
2. a feedback noise reduction path;
21. a fourth downsampling filter;
22. a feedback microphone;
23. a second analog-to-digital converter;
24. a feedback filter;
25. a second analog gain unit;
26. an amplitude limiter;
3. a time delay unit;
4. a digital-to-analog converter;
5. a feed-forward noise reduction path;
51. a feedforward microphone;
52. a first analog-to-digital converter;
53. a feed-forward downsampling filter;
54. a feedforward filter;
55. a first analog gain unit.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In one or more embodiments of the present application, the active noise reduction earphone includes a feedforward noise reduction path and a feedback noise reduction path, which are respectively connected to a digital-to-analog converter (also called D/a converter, DAC for short), where the feedforward noise reduction path is configured to collect an external noise signal outside the active noise reduction earphone and perform feedforward noise reduction on the external noise signal; the feedback noise reduction path is configured to collect an internal noise signal in the active noise reduction earphone and an audio echo signal of an audio signal to be broadcast, which is played from a player and leaks into the feedback noise reduction path, and perform feedback noise reduction on the internal noise signal, where the audio echo signal needs to be filtered by an audio echo filtering system provided in one or more embodiments of the present application, so that the internal noise signal collected in the feedback noise reduction path is not affected by the audio to be broadcast, and the following embodiments are specifically described in detail.
In order to effectively reduce the influence of the noise reduction channel on the music playing, and simultaneously, effectively reduce the sampling rate of the audio echo filtering, and effectively reduce the hardware overhead and the operation complexity, the present application provides an embodiment of an audio echo filtering system, and referring to fig. 1, the audio echo filtering system specifically includes the following contents:
An echo filtering component 11 and an up-sampling filter 12, and the echo filtering component 11 and the up-sampling filter 12 are connected to each other.
The echo filtering component 11 is configured to obtain an audio signal to be played in the active noise reduction earphone at a first sampling rate, perform filtering processing on the audio signal to be played, and output the filtered audio signal to be played to the upsampling filter 12 at the first sampling rate. Specifically, the echo filter component 11 may be connected to a player in the active noise reduction earphone, and the player is configured to play the audio signal to be broadcast in a memory in the active noise reduction earphone, where the memory is used to store the audio signal to be broadcast.
The up-sampling filter 12 is configured to output the audio signal to be broadcast, which is filtered by the echo filtering component 11, at a second sampling rate, where the second sampling rate is greater than the first sampling rate; the audio signal to be broadcast output by the up-sampling filter 12 at the second sampling rate is superimposed with the audio echo signal output by the feedback noise reduction path 2 in the active noise reduction earphone at the second sampling rate, so as to eliminate the audio echo signal in the feedback noise reduction path 2.
It is understood that the audio signal to be broadcast operates at the first sampling rate F1 with a low sampling rate in the echo filter assembly 11, and therefore the echo filter assembly 11 operates at the first sampling rate F1; after the audio signal to be broadcast passes through the echo filtering component 11, the sampling rate of the audio signal to be broadcast is changed into a second sampling rate F2 through the up-sampling filter 12.
If the signal in the feedback noise reduction path 2 is down-sampled to a very low sampling rate, for example, 16K/s, a very long time delay is caused to the down-sampling filter (for example, the third down-sampling filter 133) in the feedback noise reduction path 2 and the feedback filter 24 in the feedback noise reduction path 2, and the noise cancellation performance of the feedback noise reduction path 2 is affected. Thus, to ensure that the feedback noise reduction path 2 has a small delay, e.g., on the order of 10us, in one or more embodiments of the present application, the signal acquired by the feedback noise reduction path 2 cannot be down-sampled to a very low sampling rate, but can only be down-sampled to a moderate sampling rate, e.g., the second sampling rate F2. In a specific example, F2 can take the value of 192K/s, 384K/s or 768K/s, etc.
Whereas the feedback noise reduction path 2 can only remove lower frequency noise, e.g. below 1Khz or below 2 Khz. Thus, the echo filtering component 11 may operate at a lower sampling rate, such as the first sampling rate F1. In one embodiment, F1 can be 4K/s, 8K/s, or 16K/s. The low frequency parts, such as parts below 1Khz and 2Khz, in the audio signal to be broadcast in the feedback noise reduction path 2 are removed by the echo filtering component 11 and the up-sampling filter 12. Therefore, the feedback noise reduction path 2 does not or hardly affect the audio playing, and meanwhile, the echo filtering component 11 works at the lower first sampling rate F1, so that the order of the echo filtering component 11 can be effectively reduced, and the reduction of the order makes the storage overhead smaller; in addition, the reduction of the order and the reduction of the sampling rate can effectively reduce the operation amount.
In one or more embodiments of the present application, the upsampling filter 12 may be a filter capable of performing upsampling and low-pass filtering.
In order to effectively ensure that the audio echo filtering component 11 works at a low sampling rate and further simplify the hardware structure to reduce the hardware overhead, in an embodiment of the audio echo filtering system 1 provided by the present application, referring to fig. 2, the echo filtering component 11 in the audio echo filtering system 1 specifically includes the following contents:
a first down-sampling filter 111 and a first echo filter 112 connected to each other; the first downsampling filter 111 is configured to obtain the audio signal to be played at the first sampling rate, and send the audio signal to be played to the first echo filter 112 for filtering.
In one or more embodiments of the present application, the first downsampling filter 111 may be specifically a filter capable of implementing downsampling and low-pass filtering.
In one or more embodiments of the present application, the first echo filter 112 may be an adaptive or fixed filter. The first echo filter 112 may be an IIR structure, an FIR structure, or a hybrid IIR and FIR structure.
In order to further reduce the hardware overhead in the audio echo filtering process, in an embodiment of the audio echo filtering system 1 provided in the present application, referring to fig. 3, the upsampling filter 12 in the audio echo filtering system 1 is connected to the first echo filter 112; the up-sampling filter 12 is configured to output the audio signal to be played, which is processed and output by the first echo filter 112, at the second sampling rate.
In order to implement the adaptation of the audio echo filtering and the multiplexing of the FB path, and effectively improve the accuracy of the audio echo filtering, in an embodiment of the audio echo filtering system 1 provided in the present application, referring to fig. 4, the audio echo filtering system 1 further includes the following contents:
a filtering coefficient adaptive adjustment module 13; the filter coefficient adaptive adjustment module 13 includes a second downsampling filter 131, an adaptive echo filter 132, and a third downsampling filter 133. The second downsampling filter 131 is connected to the adaptive echo filter 132, and the second downsampling filter 131 is configured to obtain an audio signal to be played in the active noise reduction earphone at a first sampling rate, filter the audio signal to be played, and output the filtered audio signal to the adaptive filter.
In one or more embodiments of the present application, each of the second downsampling filter 131, the third downsampling filter 133, and the fourth downsampling filter 21 may be a filter capable of implementing downsampling and low-pass filtering.
The third downsampling filter 133 is connected to the fourth downsampling filter 21 in the feedback noise reduction path 2, and is configured to obtain the audio echo signal output by the fourth downsampling filter 21 at the first sampling rate, and superimpose the audio echo signal and the audio signal to be broadcasted output by the adaptive filter to generate an error signal for controlling the adaptive echo filter 132 to perform adaptive update of the filter coefficient;
the first echo filter 112 in the echo filtering component 11 performs filtering processing on the audio data to be broadcast according to the filter coefficient adjusted by the adaptive echo filter 132.
It is understood that the fourth down-sampling filter 21 in the feedback noise reduction path 2 outputs the audio echo signal with the second sampling rate F2, and then outputs the audio echo signal with the first sampling rate F1 via the third down-sampling filter 133.
The second downsampling filter 131 and the adaptive filter in the filter coefficient adaptive adjustment module 13 both operate at the first sampling rate F1, that is, the sampling rate of the audio signal to be broadcasted output by the adaptive filter is the first sampling rate F1.
It is understood that the adaptive echo filter 132 may operate in the time domain or the frequency domain or be implemented by sub-band filtering. The adaptive echo filter 132 may be iteratively completed by an error signal and an input audio signal to be broadcast with a first sampling rate F1, and may be completed by an algorithm such as LMS, RLS, or the like. The error signal is an error signal between the adaptive echo filter 132 and the third down-sampling filter 133, and the adaptive echo filter 132 may adjust its own system by using the error signals of the adaptive echo filter 132 and the third down-sampling filter 133, so that the filter coefficient of the adaptive echo filter 132 is continuously changed, and at the same time, when or after each time the filter coefficient is changed, the adaptive echo filter 132 may output the latest filter coefficient to the first echo filter 112, so that the first echo filter 112 performs filtering processing on the audio data to be broadcasted according to the filter coefficient adjusted by the adaptive echo filter 132.
Based on this, adopt self-adaptation echo filter 132, can adapt to various earphone sound chambeies, can effectively reduce to measure echo filter this work load respectively to different earphone sound chambeies. On the other hand, the echo channel will vary from ear canal to ear canal and from wearer to wearer, and the adaptive echo filter 132 can be adapted to different wearers and from wearer to wearer.
In order to avoid the delay effect of the error signal and further improve the reliability and accuracy of the audio echo filtering, in an embodiment of the audio echo filtering system 1 provided in the present application, the audio echo filtering system 1 further specifically includes a read time adjustment module 14, referring to fig. 5, in an embodiment of the read time adjustment module 14:
the second downsampling filter 131 reads the audio data to be broadcasted at the time t 1; the reading time adjustment module 14 is an advanced reading module 141, connected to the first downsampling filter 111, and configured to control the first downsampling filter 111 to read the audio data to be broadcasted at time t 2; wherein time t2 is earlier than the time t 1.
In one or more embodiments of the present application, the audio data to be announced is stored in the memory, and the time when the audio to be announced enters the first downsampling filter 111 and the second downsampling filter 131 is different. The look-ahead block 141 causes the audio data to be played to enter the first downsampling filter 111 earlier. For example, the audio data to be broadcast is placed in memories a 1, a 2, …, a i, …, a N, a 1 entering the second downsampling filter 131 first and a N entering later. When at some point ti, a [ i ] enters the second downsampling filter 131, at this point a [ i + P ] is entering the first downsampling filter 111, P is a positive integer. At the first time instant P × Ts, i.e. ti-P × Ts (Ts is the sampling interval of the audio data to be broadcast), a [ i ] enters the first downsampling filter 111. The look-ahead module 141 advances the audio to be broadcast by P audio samples.
In order to avoid the time delay influence of the error signal and further improve the reliability and accuracy of the audio echo filtering, in an embodiment of the audio echo filtering system 1 provided in the present application, the audio echo filtering system 1 further includes a read time adjustment module 14, see fig. 6, in another embodiment of the read time adjustment module 14:
the first downsampling filter 111 reads the audio data to be broadcasted at time t 2; the reading time adjustment module 14 is a delay reading module 142, connected to the second downsampling filter 131, and configured to control the second downsampling filter 131 to read the audio data to be played at time t 1; wherein time t2 is earlier than the time t 1.
In one or more embodiments of the present application, the delayed read module 142 is a module capable of implementing a delayed read function, and the specific implementation manner thereof may refer to the implementation manner of the advanced read module 141.
The adaptive echo filter 132 operates at the lower first sampling rate F1, which also reduces memory overhead while significantly reducing the amount of computation. However, since the feedback noise reduction path 2 requires a smaller delay, and the error signal has a larger delay with respect to the internal noise signal collected by the feedback noise reduction path 2, this delay, including the delay of the third downsampling filter 133 and the delay of the adaptive echo processing, may be much larger than 10us, and may even be larger than 1ms or more than several ms. Therefore, the error signal cannot be used as an input to the feedback filter 24 in the feedback noise reduction path 2.
Therefore, the audio echo module output with the sampling rate F2 is obtained by the read time adjustment module 14, that is, the audio signal to be broadcast at an earlier time is read from the memory, and then passes through the second downsampling filter 131, the adaptive echo filter 132 and the upsampling filter 12, and is added or subtracted with the fourth downsampling filter 21 with the sampling rate F2 in the feedback noise reduction path 2 as the input of the feedback filter 24 in the feedback noise reduction path 2. The first echo filter 112 may be considered as a backup of the adaptive echo filter 132, which may be converted between the time domain and the frequency domain.
In order to further improve the reliability of the application of the first echo filter 112 and the accuracy of the echo filtering, in an embodiment of the audio echo filtering system 1 provided in the present application, the time difference between the time t1 and the time t2 is equal to the sum of the time delays of the first echo filter 112, the second down-sampling filter 131, and the up-sampling filter 12.
It will be appreciated that the time for the read time adjustment module 14 to advance or delay depends on the time delays of the first echo filter 112, the second down-sampling filter 131 and the up-sampling filter 12, so that the time for the read time adjustment module 14 to advance or delay is just enough for the corresponding signal to cancel the audio signal to be broadcasted output by the feedback noise reduction path 2. Therefore, the time for the read time adjustment module 14 to advance or delay may be equal to the sum of the time delays of the first echo filter 112, the second downsampling filter 131 and the upsampling filter 12.
In order to effectively simplify the design of the sampling filter and further reduce the hardware overhead and the operation complexity, in an embodiment of the audio echo filtering system 1 provided in the present application, the second sampling rate F2 is an integer multiple of the first sampling rate F1.
Specifically, the second sampling rate F2 is designed to be an integer multiple of the first sampling rate F1, which can simplify the down-sampling filter and the up-sampling filter 12.
In order to effectively reduce the influence of the noise reduction channel on the played music, and at the same time, effectively reduce the sampling rate of the audio echo filtering, and effectively reduce the hardware overhead and the operation complexity, the present application provides an embodiment of an active noise reduction system implemented by applying all or part of the contents in the audio echo filtering system 1, and referring to fig. 7, the active noise reduction system specifically includes the following contents:
a feedback noise reduction path 2 and an audio echo filtering system 1 for canceling an audio echo signal in said feedback noise reduction path 2.
Wherein the audio echo filtering system 1 comprises an echo filtering component 11 and an up-sampling filter 12; the echo filtering component 11 is configured to obtain an audio signal to be played in the active noise reduction earphone at a first sampling rate, and perform filtering processing on the audio signal to be played; the up-sampling filter 12 is configured to output the audio signal to be broadcast, which is filtered by the echo filtering component 11, at a second sampling rate, where the second sampling rate is greater than the first sampling rate; the audio signal to be broadcast output by the up-sampling filter 12 at the second sampling rate is superimposed with the audio echo signal output by the feedback noise reduction path 2 at the second sampling rate, so as to eliminate the audio echo signal in the feedback noise reduction path 2.
In order to avoid the delay effect of the audio echo filtering and further improve the reliability and accuracy of audio playing, in an embodiment of the active noise reduction system provided in the present application, referring to fig. 8, the active noise reduction system further includes the following contents:
a time delay unit 3; the delay unit 3 is connected to a digital-to-analog converter 4 in the active noise reduction earphone, and is configured to delay and output the audio signal to be broadcast in the active noise reduction earphone, so that the delayed and output audio signal to be broadcast is superimposed with the filtered internal noise signal output by the feedback noise reduction channel 2, and then output to the digital-to-analog converter 4 in the active noise reduction earphone.
In one or more embodiments of the present application, the delay unit 3 is specifically a device capable of implementing a delay function, and its specific implementation may refer to an implementation of the advanced reading module 141.
In a specific embodiment of the active noise reduction system, the feedforward noise reduction path 5 in the active noise reduction system is connected to the digital-to-analog converter 4 in the active noise reduction headphone, and is configured to collect and filter an external noise signal of the active noise reduction headphone. Referring to fig. 8, specifically:
The feedforward noise reduction path 5 consists of a feedforward microphone 51 for acquiring the external noise signal, a first analog-to-digital converter 52, a feedforward down-sampling filter 53 and a feedforward filter 54 for filtering the external noise signal which are connected in sequence; the feedforward filter 54 is connected to the digital-to-analog converter 4, so that the filtered external noise signal is superimposed with the filtered internal noise signal output by the feedback noise reduction path 2, from which the audio echo signal has been removed, and then output to the digital-to-analog converter 4 in the active noise reduction earphone.
In one or more embodiments of the present application, the feedforward filter 54 may be an adaptive or fixed filter. The feedforward filter 54 may be an IIR filter, an FIR filter, or a mixture of IIR and FIR filters.
In one or more embodiments of the present application, the feedforward downsampling filter 53 may be a filter capable of downsampling and low-pass filtering.
In order to further improve the reliability and accuracy of the feedforward filtering process, in an embodiment of the active noise reduction system, the feedforward noise reduction path 5 further includes a first analog gain unit 55 respectively connected between the feedforward microphone 51 and the first analog-to-digital converter 52; the first analog gain unit 55 is configured to amplify the external noise signal collected by the feedforward microphone 51 and output the amplified external noise signal to the first analog-to-digital converter 52.
In a specific embodiment of the active noise reduction system, the feedback noise reduction path 2 in the active noise reduction system is connected to the digital-to-analog converter 4 in the active noise reduction headphone, and is configured to collect and filter an internal noise signal of the active noise reduction headphone. Referring to fig. 8, specifically:
the feedback noise reduction path 2 is specifically composed of a feedback microphone 22, a second analog-to-digital converter 23, a fourth down-sampling filter 21 and a feedback filter 24, which are sequentially connected and used for collecting an internal noise signal and an audio echo signal of the active noise reduction earphone; the feedback filter 24 is connected to the digital-to-analog converter 4 in the active noise reduction headphone. Before the feedback filter 24 performs signal superposition with the external noise signal output by the feedforward filter 54, the internal noise signal output by the feedback filter 24 is subjected to amplitude limiting processing by an amplitude limiter 26 connected with the feedback filter 24, and then is subjected to signal superposition with the external noise signal output by the feedforward filter 54.
In one or more embodiments of the present application, the feedback filter 24 may be an adaptive or fixed filter. The feedback filter 24 may be an IIR structure, an FIR structure, or a hybrid IIR and FIR structure.
In order to further improve the reliability and accuracy of the feedforward filtering process, in an embodiment of the active noise reduction system, the feedback noise reduction path 2 further includes a second analog gain unit 25 respectively connected between the feedback microphone 22 and the second analog-to-digital converter 23; the second analog gain unit 25 is configured to amplify the internal noise signal collected by the feedback microphone 22 and output the amplified signal to the second analog-to-digital converter 23.
In one or more embodiments of the present application, the feedback microphone 22 and the feedforward microphone 51 may each be a microphone capable of picking up a sound signal. The first analog-to-digital converter 52 and the second analog-to-digital converter 23 are both analog-to-digital converters (i.e., a/D converters, or ADCs for short).
Specifically, in the active noise reduction system, the microphone collects the sound signal and converts it into an analog electrical signal (the sound collected by the feedback microphone 22 and the feedforward microphone 51 includes the ambient noise for ANC function and the music played by the player leaking into the microphone), which may be converted into a digital signal by an analog gain module and an analog-to-digital converter (ADC). The microphone is divided into two paths, which are a feedforward noise reduction path 5(FF, feed forward and a feedback noise reduction path 2(FB, feed back), and the two paths can work together or separately, a feedforward microphone 51 of the feedforward noise reduction path 5 is placed outside the earphone, a feedback microphone 22 of the feedback noise reduction path 2 is placed inside the earphone, and is close to the ear canal when worn, the feedforward microphone 51 collects an external noise signal, the external noise signal passes through a first analog gain unit 55, a first analog-to-digital converter 52, a feedforward down-sampling filter 53 and a feedforward filter 54 to be used as the input of the digital-to-analog converter 4, the feedback microphone 22 collects an internal noise signal and an audio echo signal, the internal noise signal and the audio echo signal pass through a second analog gain unit 25, a second analog-to-digital converter 23, a fourth down-sampling filter 21 and a feedback filter 24 to be used as the input of the digital-to-analog converter 4, when audio is played, the audio signal to be played is sent to the digital-to the digital converter 4 on one hand, the audio echo filtering system 1 cancels out the audio component to be broadcast in the feedback noise reduction path 2, so that the sound collected in the feedback noise reduction path 2 is not affected by the audio to be broadcast. The audio signal to be broadcast is added or subtracted from the third down-sampling filter 133 in the feedback noise reduction channel to eliminate the influence of the audio signal to be broadcast on the noise reduction channel, and then the remaining environmental noise is sent to the feedback filter 24. The signal filtered by the feedback filter 24 may pass through an amplitude limiter 26 and then be sent to the digital-to-analog converter 4 for playing, so as to complete the ANC noise reduction function and the audio signal playing function.
Based on the foregoing, the present application provides an active noise reduction headphone comprising a feedback microphone 22, a feedback filter 24, and the feedback filter 24 operating at a sampling rate F2. The audio signal to be broadcast passes through an echo filter to obtain a first multipath echo signal, the first multipath echo signal works at a sampling rate of F1, F1 is less than F2, the first multipath echo signal is processed by an up-sampling filter 12 which is F2/F1 times to obtain a second multipath echo signal, the second multipath echo signal is added or subtracted with the audio signal before the feedback filter 24, and the audio echo signal in the audio signal before the feedback filter 24 is eliminated.
The audio signal collected by the feedback microphone 22 is down-sampled to F1, the sampling rate of the audio signal to be broadcast 1 is F1 or down-sampled to F1 by a down-sampling and low-pass filter, and the two signals are used for adaptive echo processing to obtain the coefficient of the adaptive echo filter 132. And eliminating the audio echo signal in the audio signal before the feedback filter 24 by using the audio signal 2 to be broadcast, passing through a backup echo filter, passing through an F2/F1 time upsampling and low-pass filter, and adding or subtracting the audio signal before the feedback filter 24. Where the back-up echo filter is a back-up of the adaptive echo filter 132. Let the delay of the up-sampling filter 12 be T1, the delay of the back-up echo filter be T2, the delay of the down-sampling and low-pass filter be T3, and the amount T by which the reference audio signal 2 leads the reference audio signal 1 depends on T1, T2, and T3. And F2 is an integer multiple of F1, so that the audio echo filtering system 1 operates at a lower sampling rate, the order of the audio echo multi-path filter is reduced, and the reduction of the order makes the storage overhead smaller. The reduction of the order number and the reduction of the sampling rate greatly reduce the computation amount, and the audio echo filtering system 1 works at a lower sampling rate, thereby also reducing the storage overhead and greatly reducing the computation amount.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such article or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element. The terms "upper", "lower", and the like, indicate orientations or positional relationships that are based on the orientations or positional relationships shown in the drawings, are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present application. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.
The embodiments in the present specification are described in a progressive manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of an embodiment of the specification. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
The principle and the implementation mode of the present application are explained by applying specific embodiments in the present application, and the description of the above embodiments is only used to help understanding the method and the core idea of the present application; meanwhile, for a person skilled in the art, according to the idea of the present application, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present application.
Claims (12)
1. An audio echo filtering system, comprising: an echo filtering component and an up-sampling filter;
the echo filtering component is used for acquiring an audio signal to be broadcasted in the active noise reduction earphone at a first sampling rate and filtering the audio signal to be broadcasted;
the up-sampling filter is used for outputting the audio signal to be broadcasted after being filtered by the echo filtering component at a second sampling rate, and the second sampling rate is greater than the first sampling rate;
the audio signal to be broadcast output by the up-sampling filter at the second sampling rate is superposed with the audio echo signal output by the feedback noise reduction channel in the active noise reduction earphone at the second sampling rate so as to eliminate the audio echo signal in the feedback noise reduction channel;
the echo filtering assembly comprises: a first down-sampling filter and a first echo filter connected to each other;
the first down-sampling filter is used for acquiring the audio signal to be broadcasted at the first sampling rate and sending the audio signal to be broadcasted to the first echo filter for filtering;
the up-sampling filter is connected with the first echo filter;
the up-sampling filter is used for outputting the audio signal to be broadcasted which is output after being processed by the first echo filter at the second sampling rate.
2. The audio echo filtering system of claim 1, further comprising a filter coefficient adaptive adjustment module;
the filtering coefficient self-adaptive adjusting module comprises a second down-sampling filter, a self-adaptive echo filter and a third down-sampling filter;
the second downsampling filter is used for acquiring an audio signal to be broadcasted in the active noise reduction earphone at a first sampling rate, filtering the audio signal to be broadcasted and outputting the filtered audio signal to the adaptive filter;
the third down-sampling filter is connected with a fourth down-sampling filter in the feedback noise reduction path and used for acquiring an audio echo signal output by the fourth down-sampling filter at the first sampling rate, and superposing the audio echo signal and an audio signal to be broadcasted output by the adaptive filter to generate an error signal for controlling the adaptive echo filter to adaptively update a filter coefficient;
and a first echo filter in the echo filtering component carries out filtering processing on the audio data to be broadcasted according to the filtering coefficient adjusted by the self-adaptive echo filter.
3. The audio echo filtering system of claim 2, further comprising a read time adjustment module;
the second downsampling filter reads the audio data to be broadcasted at the time t 1;
the reading time adjusting module is an advanced reading module, is connected to the first downsampling filter, and is configured to control the first downsampling filter to read the audio data to be broadcasted at time t 2;
wherein time t2 is earlier than the time t 1.
4. The audio echo filtering system of claim 2, further comprising a read time adjustment module;
the first downsampling filter reads the audio data to be broadcasted at the time t 2;
the reading time adjusting module is a delay reading module, is connected to the second downsampling filter, and is configured to control the second downsampling filter to read the audio data to be broadcasted at time t 1;
wherein time t2 is earlier than the time t 1.
5. The audio echo filtering system of claim 3 or 4, wherein the time difference between time t1 and time t2 is equal to the sum of the time delays of the first echo filter, second downsampling filter, and upsampling filter.
6. The audio echo filtering system of claim 1, wherein the second sampling rate is an integer multiple of the first sampling rate.
7. An active noise reduction system, comprising: a feedback noise reduction path and an audio echo filtering system according to any one of claims 1 to 6 for canceling an audio echo signal in the feedback noise reduction path;
further comprising: a time delay unit;
the time delay unit is connected to a digital-to-analog converter in the active noise reduction earphone and is used for outputting the audio signal to be broadcast in the active noise reduction earphone in a time delay manner, so that the audio signal to be broadcast output in a time delay manner is superposed with the internal noise signal which is output by the feedback noise reduction channel and is subjected to audio echo elimination and filtering, and then the internal noise signal is output to the digital-to-analog converter in the active noise reduction earphone.
8. The active noise reduction system of claim 7, comprising: a feed-forward noise reduction path;
the feedforward noise reduction path is connected to a digital-to-analog converter in the active noise reduction earphone and used for collecting an external noise signal of the active noise reduction earphone and filtering the external noise signal.
9. The active noise reduction system of claim 8, wherein the feed-forward noise reduction path comprises: the feedforward microphone, the first analog-to-digital converter, the feedforward downsampling filter and the feedforward filter are sequentially connected and are used for collecting the external noise signal;
The feedforward filter is connected with the digital-to-analog converter.
10. The active noise reduction system of claim 9, wherein the feed-forward noise reduction path further comprises: a first analog gain unit;
the first analog gain unit is used for amplifying the external noise signal collected by the feedforward microphone and outputting the amplified signal to the first analog-to-digital converter.
11. The active noise reduction system of any of claims 7 to 10, wherein the feedback noise reduction path comprises: the feedback microphone, the second analog-to-digital converter, the fourth down-sampling filter and the feedback filter are sequentially connected and are used for collecting the internal noise signal and the audio echo signal of the active noise reduction earphone;
the feedback filter is connected with a digital-to-analog converter in the active noise reduction earphone.
12. The active noise reduction system of claim 11, wherein the feedback noise reduction path further comprises: a second analog gain unit;
the second analog gain unit is used for amplifying the internal noise signal collected by the feedback microphone and outputting the amplified signal to the second analog-to-digital converter.
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