CN107393545B - Feedback type active noise reduction system and method with flexible gain - Google Patents
Feedback type active noise reduction system and method with flexible gain Download PDFInfo
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- CN107393545B CN107393545B CN201710580540.5A CN201710580540A CN107393545B CN 107393545 B CN107393545 B CN 107393545B CN 201710580540 A CN201710580540 A CN 201710580540A CN 107393545 B CN107393545 B CN 107393545B
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; SPEECH OR AUDIO CODING OR DECODING
- G10L21/00—Processing of the speech or voice signal to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility
- G10L21/02—Speech enhancement, e.g. noise reduction or echo cancellation
- G10L21/0208—Noise filtering
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; SPEECH OR AUDIO CODING OR DECODING
- G10L21/00—Processing of the speech or voice signal to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility
- G10L21/02—Speech enhancement, e.g. noise reduction or echo cancellation
- G10L21/0208—Noise filtering
- G10L21/0216—Noise filtering characterised by the method used for estimating noise
- G10L21/0232—Processing in the frequency domain
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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
- H04R3/04—Circuits for transducers, loudspeakers or microphones for correcting frequency response
Abstract
The invention provides a feedback type active noise reduction system with flexible gain and a method thereof, wherein the noise reduction system comprises: a transducer, a loudspeaker and a feedback filtering unit. The transducer converts acoustic signals at a certain position into electric signals, the electric signals are input into the feedback filtering unit and processed to output noise reduction signals, the noise reduction signals are converted into noise elimination waves through the loudspeaker, the noise elimination waves and noise are superposed to generate destructive interference, and the noise reduction effect is achieved. Meanwhile, the gain of the feedback filter is adjusted on line by monitoring the output amplitude of the feedback filter circuit, so that the stability of the noise reduction system is ensured, and the robustness of the noise reduction system is improved.
Description
Technical Field
The invention relates to the technical field of active noise reduction, in particular to a feedback type active noise reduction system with flexible gain and a method thereof.
Background
The active noise reduction technology is also called as active noise reduction technology, and is to generate sound waves with the same amplitude and the opposite phase with the external noise by a sound generating device to neutralize the noise, so that the noise reduction effect is realized. According to different topological structures, the methods adopted by active noise reduction are divided into a feed-forward method and a feedback method. The feedforward type utilizes a feedforward control method to design a noise reduction filter, and the method has no system stability problem, but has small noise reduction depth and unobvious noise reduction effect. The feedback type utilizes a feedback control method to design a noise reduction filter, so that the noise reduction depth is large, the noise reduction effect is obvious, and the problem of system stability exists.
Different noise environments have different noise frequency domain characteristics, so that the noise reduction performance of the feedback filter adopting fixed parameters cannot be guaranteed, moreover, the wearing habits of noise reduction earphone users can cause the difference of the acoustic characteristics of the noise reduction system, the difference can further worsen the noise reduction effect, and the feedback system is caused to generate over-regulation or unstable howling. In this case, not only the noise cannot be eliminated, but also the noise is enhanced.
Disclosure of Invention
The invention provides a feedback filter with flexible gain in order to ensure the noise reduction effect and improve the stability of a feedback noise reduction system, and particularly relates to a feedback type active noise reduction system with flexible gain and a method thereof.
To achieve the above object, the present invention provides a feedback active noise reduction system with flexible gain, the active noise reduction system comprising: a transducer, a loudspeaker and a feedback filtering unit. The feedback filtering unit comprises an analog-to-digital conversion circuit, a feedback filtering circuit, a variable gain module and a digital-to-analog conversion circuit.
The energy converter converts the detected noise sound signal into an electric signal and outputs the electric signal to the feedback filter unit, an analog/digital conversion circuit of the feedback filter unit receives the electric signal and converts the electric signal into a digital signal and outputs the digital signal to the feedback filter circuit, the digital/analog conversion circuit processes the digital signal and outputs a noise elimination signal to the digital/analog conversion circuit, the digital/analog conversion circuit converts the noise elimination signal into an analog signal and transmits the analog signal to the loudspeaker, the loudspeaker converts the signal into a sound signal, and the noise reduction sound wave and the environmental noise sound wave are superposed to generate destructive interference so as to achieve the noise reduction effect. And meanwhile, the output of the feedback filter circuit is transmitted to the variable gain module, a gain value is output after the calculation of the variable gain module, and the gain value is output to the feedback filter circuit and is used for correcting the gain of the current filter.
Furthermore, the filter parameters of the feedback filter circuit adopt an off-line design method.
Further, the gain of the feedback filter is adjusted on-line according to the output value of the filter circuit.
Further, the output of the variable gain module is in a functional relationship with the output of the feedback noise reduction filter.
The invention also provides a feedback type active noise reduction method with flexible gain, which comprises the following steps:
measuring a noise signal by using a transducer, and analyzing the frequency characteristic of the noise;
step (2) designing a feedback filter off line based on the noise frequency characteristic;
step (3) utilizing the feedback filter obtained in the step (2) to eliminate noise on line;
and (4) utilizing the output value of the real-time detection feedback filter circuit to online correct the gain of the feedback filter, and ensuring that the output of the feedback filter circuit does not exceed a preset threshold value.
Compared with the prior art, the invention has the advantages that: aiming at different noise environments, the output of the feedback filter is controlled by adjusting the gain of the feedback filter on line, so that the stability of the noise reduction system is effectively ensured, and the robustness of the system is improved. Because the gain adjustment requirement is determined according to whether the output of the feedback filter circuit exceeds a preset threshold value or not, the gain of the feedback filter is kept unchanged under the condition that the output of the feedback filter circuit does not exceed the threshold value, on one hand, the online calculation amount is reduced, and the implementation is simple; on the other hand, the influence of the adjustment of the gain on the noise reduction performance of the system is reduced to a smaller range.
Drawings
FIG. 1 is a block diagram of a feedback active noise reduction system with flexible gain;
FIG. 2 is a schematic diagram of a feedback filter design;
FIG. 3 is a graph of feedback filter gain as a function of feedback filter output.
Detailed Description
For further understanding of the technical solutions and features of the present invention, the present invention is further described below with reference to the accompanying drawings and examples.
The present embodiment provides a feedback active noise reduction system based on variable gain. Referring to fig. 1, the system includes a transducer, a speaker, and a feedback filtering unit. The feedback control unit comprises an analog-to-digital conversion circuit, a feedback filter circuit, a variable gain module and a digital-to-analog conversion circuit.
In an embodiment the transducer is determined to be a microphone.
The microphone converts the detected noise sound signal into an electric signal and outputs the electric signal to the feedback filter unit, an analog/digital conversion circuit of the feedback filter unit receives the electric signal of the noise, converts the electric signal into a digital signal and outputs the digital signal to the feedback filter circuit, the digital signal is processed by the feedback filter circuit and then outputs a noise reduction signal, the noise reduction signal is output to the digital/analog conversion circuit and is converted into an analog signal by the digital-analog conversion circuit and then output to the loudspeaker, the loudspeaker converts the analog noise reduction electric signal into a sound signal, and the noise reduction sound wave interacts with the environmental noise sound wave to achieve the noise reduction effect. And meanwhile, an output signal of the feedback filter circuit is transmitted to the variable gain module, a gain adjusting signal is output after the calculation of the variable gain module, and the signal is output to the feedback filter circuit and used for correcting the gain of the current feedback filter. The noise that is not cancelled is again detected by the microphone and the process loops until the noise is minimized.
The feedback filter needs to be designed off-line based on the noise frequency characteristics. Design of noise reduction system using feedback filter the principle of noise reduction system is illustrated in fig. 2, where K denotes the feedback filter gain, H denotes the feedback filter transfer function and G denotes the loudspeaker transfer characteristic transfer function. In order to ensure that the noise reduction effect is optimal, K and H can meet the requirements
Namely: make it
The minimum two-norm.
Because the feedback filters with fixed parameters have different noise elimination effects on different noise environments, in order to prevent howling or instability of a noise reduction system caused by overshoot of the feedback filters in the noise elimination process, the gain of the filters is dynamically adjusted by using the variable gain unit based on the output values of the feedback filters. Referring to fig. 3, a threshold value y0 is set for the output of the feedback filter, and if the output value is within the threshold value range, the current filter gain k0 is kept unchanged; if the output value exceeds the threshold value, the gain of the filter is adjusted on line according to the output of the filter, the more the output value exceeds the threshold value, the smaller the gain drop, and the filter gain value is adjusted for multiple times until the output value of the feedback filter does not exceed the threshold value. The part of the feedback filter exceeding the threshold value is monotonically decreased in relation to the gain, and may be linearly monotonically decreased as shown in fig. 3, or may be non-linearly monotonically decreased, and the functional relationship of the part may depend on the actual situation.
The invention also provides an active noise reduction method with a flexible gain feedback filter, and the embodiment executes the following steps:
step (1) measuring a noise signal by using a microphone, and analyzing the frequency characteristic of the noise: carrying out Fourier transform on the noise signals collected by the microphone to obtain distribution curves of the noise signals in each frequency band;
step (2) designing a feedback filter off line based on the noise frequency characteristic: and (3) setting a feedback filter based on the noise frequency domain characteristic curve and the loudspeaker sound transmission characteristic in the step (1), and ensuring the stability of a noise reduction system.
And (3) eliminating noise on line by using the feedback filter obtained in the step (2): and (3) eliminating noise on line by using a feedback filter designed off line, and monitoring the output signal of the filter in real time.
And (4) utilizing the output value of the real-time detection feedback filter circuit to online correct the gain of the feedback filter, and ensuring that the output of the feedback wave circuit does not exceed a preset threshold value. If the output of the filter exceeds a threshold value, reducing the gain of the filter; and if the output of the filter is within the threshold value range, keeping the gain of the filter unchanged.
The active noise reduction system and method with the flexible gain feedback filter according to the embodiments of the present invention are described in detail above, and the description of the embodiments is only for assisting understanding the core idea of the present invention. For those skilled in the art, variations can be made in the specific embodiments and applications without departing from the spirit of the invention. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (5)
1. A feedback type active noise reduction system with flexible gain is characterized in that: the active noise reduction system includes: the device comprises a transducer, a loudspeaker and a feedback filtering unit, wherein the feedback filtering unit comprises an analog-to-digital conversion circuit, a feedback filtering circuit, a variable gain module and a digital-to-analog conversion circuit;
the transducer converts the detected acoustic signal into an electric signal and outputs the electric signal to the feedback filtering unit, and the mode of the feedback filtering unitThe digital-to-analog conversion circuit receives the electric signal, converts the electric signal into a digital signal and outputs the digital signal to the feedback filter circuit, the digital-to-analog conversion circuit processes the digital signal and outputs a noise elimination signal to the digital-to-analog conversion circuit, the digital-to-analog conversion circuit converts the noise elimination signal into an analog signal and transmits the analog signal to the loudspeaker, the loudspeaker converts the signal into an acoustic signal, and the noise reduction acoustic wave and the environmental noise acoustic wave are superposed to generate destructive interference so as to achieve the noise reduction effect; meanwhile, the output of the feedback filter circuit is transmitted to the variable gain module, a gain value is output after the calculation of the variable gain module, and the gain value is output to the feedback filter circuit and used for correcting the gain of the current filter; the feedback filter needs to be designed off-line based on the noise frequency characteristic, and in order to ensure the optimal noise reduction effect, the K and H requirements meet the formula
Namely: make it
Where K represents the feedback filter gain, H represents the feedback filter transfer function, and G represents the loudspeaker transfer characteristic transfer function.
2. The feedback active noise reduction system with compliant gain of claim 1, wherein: the gain of the feedback filter is adjusted on-line according to the output value of the filter circuit.
3. The feedback active noise reduction system with compliance gain of claim 2, wherein: the output of the variable gain module is in a functional relation with the output of the feedback noise reduction unit.
4. The feedback active noise reduction system with compliance gain of claim 2, wherein: and setting a threshold value output by the feedback noise reduction unit, wherein the output exceeds the threshold value, and the variable gain module adjusts the gain of the feedback filter until the output of the feedback noise reduction unit does not exceed the threshold value.
5. A method of feedback active noise reduction with a compliance gain, using the system of claim 1, comprising the steps of:
measuring a noise signal by using a transducer, and analyzing the frequency characteristic of the noise;
step (2) designing a feedback filter off line based on the noise frequency characteristic;
step (3) utilizing the feedback filter obtained in the step (2) to eliminate noise on line;
and (4) utilizing the output value of the real-time detection feedback filter circuit to online correct the gain of the feedback filter, and ensuring that the output of the feedback filter circuit does not exceed a preset threshold value.
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| CN107945784A (en) * | 2017-12-14 | 2018-04-20 | 成都必盛科技有限公司 | A kind of automatic calibrating method and device of active noise reduction audio frequency apparatus |
| CN108260069A (en) * | 2018-01-23 | 2018-07-06 | 歌尔股份有限公司 | The debugging system and method for a kind of noise cancelling headphone |
| CN108847209A (en) * | 2018-06-01 | 2018-11-20 | 会听声学科技（北京）有限公司 | A kind of denoising device and noise-reduction method |
| 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 |
| CN111447523B (en) * | 2020-03-31 | 2022-02-18 | 歌尔科技有限公司 | Earphone, noise reduction method thereof and computer readable storage medium |
| CN113676804B (en) * | 2020-05-14 | 2023-07-18 | 华为技术有限公司 | Active noise reduction method and device |
| CN112218206B (en) * | 2020-09-28 | 2022-07-19 | 业泓科技(成都)有限公司 | Sound control method, device, equipment and medium based on film loudspeaker |
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