CN109348362B - Active noise reduction system and method for eliminating bottom noise interference - Google Patents
Active noise reduction system and method for eliminating bottom noise interference Download PDFInfo
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- CN109348362B CN109348362B CN201810951362.7A CN201810951362A CN109348362B CN 109348362 B CN109348362 B CN 109348362B CN 201810951362 A CN201810951362 A CN 201810951362A CN 109348362 B CN109348362 B CN 109348362B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R3/00—Circuits for transducers, loudspeakers or microphones
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2410/00—Microphones
- H04R2410/01—Noise reduction using microphones having different directional characteristics
Abstract
The invention provides an active noise reduction system for eliminating bottom noise interference, which comprises at least one noise reduction channel, wherein the noise reduction channel comprises a microphone, an AD converter, a noise reduction filter and a DA converter, wherein a programmable gain amplifier is connected between the microphone and the AD converter and is used for adjusting an input signal of the microphone; a first dynamic range expansion module is connected between the AD converter and the noise reduction filter and used for expanding the dynamic range of the AD converter; the second dynamic range expansion module is connected between the noise reduction filter and the DA converter and used for expanding the dynamic range of the DA converter.
Description
Technical Field
The invention relates to the technical field of signal processing, in particular to an active noise reduction system and method for eliminating background noise interference.
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).
In the existing active noise reduction scheme, the noise is easily affected by external low frequency noise, so as to generate "puffs" and "pops" sounds. The pure active noise reduction earphone can influence a person to receive signals such as external voice and the like, inconvenience is caused to the person in a specific occasion, active noise reduction is performed when music is played, low-frequency components of the music are easily eliminated, and the weight of music playing is reduced. In addition, in the active noise reduction earphone adopting digital signal processing in the prior art, due to the limited dynamic ranges of the AD converter and the DA converter, a "hoarse" noise is easily generated, or "pop" and "pop" noises are easily generated, so that an effective noise reduction effect is difficult to achieve.
Therefore, in order to solve the problems in the prior art, an active noise reduction system and method for eliminating noise floor interference are needed.
Disclosure of Invention
One aspect of the present invention is to provide an active noise reduction system for eliminating noise floor interference, the system includes at least one noise reduction channel, the noise reduction channel includes a microphone, an AD converter, a noise reduction filter and a DA converter, wherein a Programmable Gain Amplifier (PGA) is connected between the microphone and the AD converter for adjusting an input signal of the microphone;
a first dynamic range extension module (DRE) is connected between the AD converter and the noise reduction filter for extending the dynamic range of the AD converter.
Preferably, the first dynamic range extension module comprises a first low-delay filter, a first down-sampling module, a second low-delay filter, a second down-sampling module and a signal amplitude detection module, wherein a digital gain module is arranged between the first down-sampling module and the first low-delay filter or between the first down-sampling module and the second low-delay filter.
Preferably, the digital gain module is configured to compensate for a gain change of the programmable gain amplifier.
Preferably, the digital gain module operates at a first sampling rate, and the signal amplitude detection module operates at a second sampling rate, wherein the first sampling rate is greater than the second sampling rate.
Preferably, a second dynamic range extension module is connected between the noise reduction filter and the DA converter for extending the dynamic range of the DA converter
Preferably, the noise reduction path is a feed-forward noise reduction path and/or a feedback noise reduction path.
Another aspect of the present invention is to provide an active noise reduction method for eliminating noise floor interference, the method comprising the steps of:
the microphone collects environmental noise, and the programmable gain amplifier adjusts an input signal of the microphone;
the first dynamic range expansion module expands the dynamic range of the output signal of the AD converter and sends the signal to a noise reduction filter for noise reduction processing;
and the second dynamic range expansion module expands the dynamic range of the output signal of the noise reduction filter and sends the dynamic range to the DA converter.
Preferably, the programmable gain amplifier adjusting the input signal of the microphone comprises the steps of:
increasing the gain of the programmable gain amplifier when a small signal is input;
when a large signal is input, the gain of the programmable gain amplifier is lowered.
Preferably, the gain variation of the programmable gain amplifier is compensated by a digital gain module.
Preferably, the gain variation of the programmable gain amplifier is adjusted by the signal amplitude detection module as follows:
determining a gain range of the programmable gain amplifier, and selecting a first signal threshold and a second signal threshold, wherein the first signal threshold is smaller than the second signal threshold;
detecting the signal amplitude of the input signal, and increasing the gain of the programmable gain amplifier when the signal amplitude of the input signal is smaller than a first signal threshold and is smaller than a first target after being amplified by the gain of the programmable gain amplifier;
when the signal amplitude of the input signal is smaller than a first signal threshold value and is larger than or equal to a first target after being amplified by the gain of the programmable gain amplifier, the gain of the programmable gain amplifier is unchanged;
when the signal amplitude of the input signal is greater than the second signal threshold value and the signal amplitude of the input signal is greater than the second target after being amplified by the gain of the programmable gain amplifier, reducing the gain of the programmable gain amplifier;
when the signal amplitude of the input signal is greater than the second signal threshold and the signal amplitude of the input signal is less than or equal to the second target after being amplified by the gain of the programmable gain amplifier, the gain of the programmable gain amplifier is unchanged;
when the signal amplitude of the input signal is between the first signal threshold and the second signal threshold, the gain of the programmable gain amplifier is unchanged.
According to the active noise reduction system and method for eliminating the background noise interference, dynamic range expansion modules are respectively added to the AD converter and the DA converter, the dynamic ranges of the AD converter and the DA converter are expanded, and the background noise of the noise reduction earphone is reduced.
The invention relates to an active noise reduction system and method for eliminating bottom noise interference, wherein an AD converter is additionally provided with a first dynamic range expansion module, a digital gain module of the first dynamic range expansion module works at a first sampling rate, a signal amplitude detection module works at a second sampling rate, and the first sampling rate is greater than the second sampling rate, so that more sdm noises can be filtered, the amplitude of an input signal can be accurately detected, and the time error of gain variation of the digital gain module and a Programmable Gain Amplifier (PGA) can be reduced.
The invention relates to an active noise reduction system and method for eliminating bottom noise interference, wherein a gain range is set by a programmable gain amplifier, a first signal threshold (TH1) and a second signal threshold (TH2) are selected in the gain range, and the gain is adjusted through the first signal threshold (TH1) and the second signal threshold (TH2), so that the dynamic range of an AD converter is expanded, the frequency of gain change of the Programmable Gain Amplifier (PGA) is reduced, and the influence of gain change of the Programmable Gain Amplifier (PGA) on the signal-to-noise ratio (SNR) is reduced.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
Drawings
Further objects, features and advantages of the present invention will become apparent from the following description of embodiments of the invention, with reference to the accompanying drawings, in which:
fig. 1 schematically shows a block diagram of an active noise reduction system for eliminating noise floor interference according to an embodiment of the present invention.
Fig. 2 shows a block diagram of a first dynamic expansion module according to the present invention.
Fig. 3 shows a schematic diagram of gain variation adjustment for a programmable gain amplifier of the present invention.
Detailed Description
The objects and functions of the present invention and methods for accomplishing the same will be apparent by reference to the exemplary embodiments. However, the present invention is not limited to the exemplary embodiments disclosed below; it can be implemented in different forms. The nature of the description is merely to assist those skilled in the relevant art in a comprehensive understanding of the specific details of the invention.
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, and related technical terms should be well known to those skilled in the art. In the drawings, the same reference numerals denote the same or similar parts, or the same or similar steps, unless otherwise specified. The following describes an active noise reduction system and method for eliminating background noise interference in detail through specific embodiments, and according to an embodiment of the present invention, an active noise reduction system for eliminating background noise interference includes at least one noise reduction channel. Referring to fig. 1, a block diagram of an active noise reduction system for eliminating noise floor interference according to an embodiment of the present invention is shown, where the noise reduction channels in this embodiment include a feedforward noise reduction channel and a feedback noise reduction channel, and in some embodiments, may be only the feedforward noise reduction channel or only the feedback noise reduction channel.
According to the invention, the noise reduction channel comprises a microphone, an AD converter, a noise reduction filter and a DA converter, wherein a programmable gain amplifier is connected between the microphone and the AD converter for adjusting the input signal of the microphone.
A first dynamic range expansion module is connected between the AD converter and the noise reduction filter and used for expanding the dynamic range of the AD converter; and a second dynamic range expansion module is connected between the noise reduction filter and the DA converter and is used for expanding the dynamic range of the DA converter.
In the present embodiment, the feedforward noise reduction path includes a feedforward microphone 101, an AD converter 103, a feedforward noise reduction filter 105, and a DA converter 107.
A Programmable Gain Amplifier (PGA)102 is connected between the feedforward microphone 101 and the AD converter 103 for adjusting the input signal of the microphone (feedforward microphone 101).
A first dynamic range extension module (DRE) is connected between the AD converter 103 and the feedforward noise reduction filter 105 for extending the dynamic range of the AD converter; a second dynamic range extension module (DRE) is connected between the feedforward noise reduction filter and the DA converter 107 for extending the dynamic range of the DA converter 107.
In this embodiment, the feedback noise reduction channel has a structure similar to that of the feedforward noise reduction channel, and specifically, the feedback noise reduction channel includes a feedback microphone, an AD converter, and a feedback noise reduction filter.
A Programmable Gain Amplifier (PGA) is connected between the feedforward microphone and the AD converter for adjusting the input signal of the microphone (feedback microphone).
A dynamic range extension module (DRE) is connected between the AD converter and the feedback noise reduction filter for extending the dynamic range of the AD converter. The feedback noise reduction filter and the feedforward noise reduction filter are superimposed on the signal by an adder, and a second dynamic range extension module (DRE) extends the dynamic range of the DA converter 107.
The microphone audio input has a large dynamic range, and when a small signal is input, due to the noise floor generated by the AD converter, the noise floor of the "hissing" sound is easily heard when the noise is actively reduced (feedforward noise reduction and/or feedback noise reduction). When the movement causes low-frequency noise or the vehicle bumps (such as a deceleration strip) when the vehicle is sitting, the microphone can generate large low-frequency noise when the cavity is pressed by hands for the headset. The low frequency noise is often below 100hz, and the signal amplitude may be relatively large. If the low noise collected by the microphone is saturated at the AD converter, the noise is easily generated as "pop" and "pop" noises. The invention has great expansion to the dynamic range of the output signal of the AD converter through the dynamic range expansion module (DRE).
As shown in fig. 2, a structural block diagram of the first dynamic range extension module of the present invention, according to an embodiment of the present invention, the first dynamic range extension module 104 includes a first low-delay filter 201, a first downsampling module 203, a second low-delay filter 204, a second downsampling module 205, and a signal amplitude detection module 206, which are connected in sequence.
A digital gain module is arranged between the first down-sampling module 203 and the first low-delay filter 201 or between the first down-sampling module 203 and the second low-delay filter 204. For example, in some embodiments, a Digital gain module (Digital gain)202 is disposed between the first downsampling module 203 and the first low-latency filter 201; in other embodiments, a Digital gain module (Digital gain) 202' is disposed between the first downsampling module 203 and the second low-delay filter 204.
In the following embodiments, taking the example that a Digital gain module (Digital gain)202 is disposed between the first downsampling module 203 and the first low-delay filter 201, the Digital gain module 202 is configured to compensate for a gain variation of the programmable gain amplifier 102. The digital gain module operates at a first sampling rate f1 and the signal amplitude detection module operates at a second sampling rate f2, wherein the first sampling rate f1 is greater than the second sampling rate f 2. In order to synchronize the gain variation of the programmable gain amplifier 102 with the digital gain module 202, the present invention employs a higher sampling rate (first sampling rate f1), and simultaneously, in order to filter more sdm noise and accurately detect the amplitude of the input signal, the signal amplitude detection module 206 employs a lower sampling rate (second sampling rate f2), and the first sampling rate f1 and the second sampling rate f2 satisfy that the first sampling rate f1 is greater than the second sampling rate f 2. The signal detection module 206 detects the amplitude of the input signal, and feeds back the detected amplitude to the programmable gain amplifier 102 and the Digital gain module (Digital gain)202 for signal amplitude adjustment.
It should be understood that the structure of the first dynamic range extension module in the feedforward noise reduction channel described above has the same dynamic range extension module in the feedback noise reduction channel, and details are not described in the embodiments.
Still taking a feedforward noise reduction channel as an example, an active noise reduction method for eliminating the noise floor interference according to the present invention is explained below, and according to the embodiment of the present invention, the active noise reduction method for eliminating the noise floor interference includes the following steps:
ambient noise is picked up by microphones (feedforward and/or feedback microphones) and the programmable gain amplifier adjusts the input signal to the microphone.
The first dynamic range expansion module expands the dynamic range of the output signal of the AD converter and sends the signal to a noise reduction filter for noise reduction processing;
and the second dynamic range expansion module expands the dynamic range of the output signal of the noise reduction filter and sends the dynamic range to the DA converter.
The programmable gain amplifier 102 adjusting the input signal of the microphone comprises the following steps:
when a small signal is input, the gain of the programmable gain amplifier is increased. When the input signal is small, the gain of the Programmable Gain Amplifier (PGA)102 is increased, which is beneficial to improving the signal-to-noise ratio (SNR) when the signal is small, and reducing the background noise of 'hissing' sound when the active noise reduction is carried out.
When a large signal is input, the gain of the programmable gain amplifier is lowered. When a large signal is input, the gain of the Programmable Gain Amplifier (PGA)102 is reduced, so that saturation of the large signal, especially a low-frequency large signal, at the AD converter can be avoided, and noise of "pop" and "pop" can be prevented.
When the input signal is large, in order to make the gain of the whole channel (in this embodiment, the feedforward noise reduction channel) constant, the first dynamic range extension module 104 includes a digital gain module 202, and the gain variation of the programmable gain amplifier 102 is compensated by the digital gain module 202.
According to the embodiment of the invention, the programmable gain amplifier 102 adjusts the input signal of the microphone through gain variation, the digital gain module 202 compensates the gain variation of the programmable gain amplifier, and the signal amplitude detection module detects the signal amplitude of the input signal and feeds the signal amplitude back to the programmable gain amplifier 102 and the digital gain module 202.
The digital gain module operates at a first sampling rate f1 and the signal amplitude detection module operates at a second sampling rate f2, wherein the first sampling rate f1 is greater than the second sampling rate f 2. In order to synchronize the gain variation of the programmable gain amplifier 102 with the digital gain module 202, the present invention employs a higher sampling rate (first sampling rate f1), and simultaneously, in order to filter more sdm noise and accurately detect the amplitude of the input signal, the signal amplitude detection module 206 employs a lower sampling rate (second sampling rate f2), and the first sampling rate f1 and the second sampling rate f2 satisfy that the first sampling rate f1 is greater than the second sampling rate f 2. The signal detection module 206 detects the signal amplitude of the input signal, and feeds the signal amplitude back to the programmable gain amplifier 102 and the Digital gain module (Digital gain)202 for signal amplitude adjustment.
Referring to fig. 3, a schematic diagram of the gain variation adjustment of the programmable gain amplifier of the present invention, according to an embodiment of the present invention, the gain variation of the programmable gain amplifier 102 is adjusted by the signal amplitude detection module 206 as follows.
Determining the Gain range of the programmable Gain amplifier, namely the interval between the minimum Gain and the maximum Gain ([ Gain _ low Gain _ high ] db), and selecting a first signal threshold (TH1) and a second signal threshold (TH2), wherein the first signal threshold is smaller than the second signal threshold (TH1 < TH 2).
The signal amplitude detection module 206 detects the signal amplitude of the input signal, and when the signal amplitude of the input signal is smaller than the first signal threshold (TH1) and the signal amplitude of the input signal is smaller than the first Target (Target1) after being amplified by the gain of the programmable gain amplifier, the gain of the programmable gain amplifier is increased, so that the signal amplitude of the input signal gradually approaches the first Target value (Target1) after being amplified by the gain of the programmable gain amplifier.
When the signal amplitude of the input signal is smaller than the first signal threshold (TH1), and the signal amplitude of the input signal is larger than or equal to the first Target (Target1) after being amplified by the gain of the programmable gain amplifier, the gain of the programmable gain amplifier is unchanged.
When the signal amplitude of the input signal is greater than the second signal threshold (TH2) and the signal amplitude of the input signal is greater than the second Target (Target2) after being amplified by the gain of the programmable gain amplifier, the gain of the programmable gain amplifier is reduced, so that the signal amplitude of the input signal gradually approaches the second Target value (Target2) after being amplified by the gain of the programmable gain amplifier.
When the signal amplitude of the input signal is greater than the second signal threshold (TH2), and the signal amplitude of the input signal is less than or equal to the second Target (Target2) after being amplified by the gain of the programmable gain amplifier, the gain of the programmable gain amplifier is unchanged.
When the signal amplitude of the input signal is between the first signal threshold and the second signal threshold, the gain of the programmable gain amplifier is unchanged.
The invention calibrates the gain of each programmable gain amplifier in order to prevent the deviation between the nominal gain and the actual measurement gain of the programmable gain amplifier. In order to avoid DC (direct current) variation caused by gain step variation of the programmable gain amplifier, DC calibration is performed for the gain of each programmable gain amplifier.
According to the active noise reduction system and method for eliminating the background noise interference, dynamic range expansion modules are respectively added to the AD converter and the DA converter, the dynamic ranges of the AD converter and the DA converter are expanded, and the background noise of the noise reduction earphone is reduced.
The invention relates to an active noise reduction system and method for eliminating bottom noise interference, wherein an AD converter is additionally provided with a first dynamic range expansion module, a digital gain module of the first dynamic range expansion module works at a first sampling rate, a signal amplitude detection module works at a second sampling rate, and the first sampling rate is greater than the second sampling rate, so that more sdm noises can be filtered, the amplitude of an input signal can be accurately detected, and the time error of gain variation of the digital gain module and a Programmable Gain Amplifier (PGA) can be reduced.
The invention relates to an active noise reduction system and method for eliminating bottom noise interference, wherein a gain range is set by a programmable gain amplifier, a first signal threshold (TH1) and a second signal threshold (TH2) are selected in the gain range, and the gain is adjusted through the first signal threshold (TH1) and the second signal threshold (TH2), so that the dynamic range of an AD converter is expanded, the frequency of gain change of the Programmable Gain Amplifier (PGA) is reduced, and the influence of gain change of the Programmable Gain Amplifier (PGA) on the signal-to-noise ratio (SNR) is reduced.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
Claims (9)
1. An active noise reduction system for eliminating bottom noise interference, which is characterized in that the system comprises at least one noise reduction channel, wherein the noise reduction channel comprises a microphone, an AD converter, a noise reduction filter and a DA converter, and a programmable gain amplifier is connected between the microphone and the AD converter and used for adjusting an input signal of the microphone;
connecting a first dynamic range expansion module between the AD converter and the noise reduction filter for expanding a dynamic range of the AD converter,
the first dynamic range extension module comprises a first low-delay filter, a first down-sampling module, a second low-delay filter, a second down-sampling module and a signal amplitude detection module, wherein a digital gain module is arranged between the first down-sampling module and the first low-delay filter or between the first down-sampling module and the second low-delay filter.
2. The system of claim 1, wherein the digital gain module is configured to compensate for gain variations of the programmable gain amplifier.
3. The system of claim 1, wherein the digital gain module operates at a first sampling rate and the signal amplitude detection module operates at a second sampling rate, wherein the first sampling rate is greater than the second sampling rate.
4. The system according to claim 1, characterized in that a second dynamic range extension module is connected between the noise reduction filter and the DA-converter for extending the dynamic range of the DA-converter.
5. The system of any of claims 1 to 4, wherein the noise reduction channel is a feed-forward noise reduction path and/or a feedback noise reduction path.
6. An active noise reduction method for eliminating background noise interference, the method comprising the steps of:
the microphone collects environmental noise, and the programmable gain amplifier adjusts an input signal of the microphone;
the first dynamic range expansion module expands the dynamic range of the output signal of the AD converter and sends the signal to a noise reduction filter for noise reduction processing, wherein,
the first dynamic range extension module comprises a first low-delay filter, a first down-sampling module, a second low-delay filter, a second down-sampling module and a signal amplitude detection module, wherein a digital gain module is arranged between the first down-sampling module and the first low-delay filter or between the first down-sampling module and the second low-delay filter;
and the second dynamic range expansion module expands the dynamic range of the output signal of the noise reduction filter and sends the dynamic range to the DA converter.
7. The method of claim 6, wherein the programmable gain amplifier adjusting the input signal of the microphone comprises the steps of:
increasing the gain of the programmable gain amplifier when a small signal is input;
when a large signal is input, the gain of the programmable gain amplifier is lowered.
8. The method of claim 6 or 7, wherein the gain variation of the programmable gain amplifier is compensated for by a digital gain module.
9. The method of claim 7, wherein the gain change of the programmable gain amplifier is adjusted by the signal amplitude detection module as follows:
determining a gain range of the programmable gain amplifier, and selecting a first signal threshold and a second signal threshold, wherein the first signal threshold is smaller than the second signal threshold;
detecting the signal amplitude of the input signal, and increasing the gain of the programmable gain amplifier when the signal amplitude of the input signal is smaller than a first signal threshold and is smaller than a first target after being amplified by the gain of the programmable gain amplifier;
when the signal amplitude of the input signal is smaller than a first signal threshold value and is larger than or equal to a first target after being amplified by the gain of the programmable gain amplifier, the gain of the programmable gain amplifier is unchanged;
when the signal amplitude of the input signal is greater than the second signal threshold value and the signal amplitude of the input signal is greater than the second target after being amplified by the gain of the programmable gain amplifier, reducing the gain of the programmable gain amplifier;
when the signal amplitude of the input signal is greater than the second signal threshold and the signal amplitude of the input signal is less than or equal to the second target after being amplified by the gain of the programmable gain amplifier, the gain of the programmable gain amplifier is unchanged;
when the signal amplitude of the input signal is between the first signal threshold and the second signal threshold, the gain of the programmable gain amplifier is unchanged.
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| CN110225429B (en) * | 2019-06-12 | 2020-12-04 | 会听声学科技（北京）有限公司 | Active noise reduction method and device and earphone |
| CN113676803B (en) * | 2020-05-14 | 2023-03-10 | 华为技术有限公司 | Active noise reduction method and device |
| CN112752195B (en) * | 2020-12-30 | 2023-01-31 | 恒玄科技(上海)股份有限公司 | Audio power amplifier processing method and audio power amplifier system for earphone |
| CN113242507A (en) * | 2021-06-16 | 2021-08-10 | 云茂互联智能科技(厦门)有限公司 | Method for quickly adjusting microphone gain and detecting microphone background noise |
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Address after: 201306 room 904, No. 800, Huanhu West 2nd Road, Lingang New Area, China (Shanghai) pilot Free Trade Zone, Pudong New Area, Shanghai Applicant after: Hengxuan Technology (Shanghai) Co., Ltd Address before: 200135 Shanghai 647 free trade pilot area, 171 Pudong New Area Road, 1 buildings, 6 rooms Applicant before: Heng Xuan Technology (Shanghai) Co., Ltd. |
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