WO2011012054A1

WO2011012054A1 - Method and device for eliminating background noise

Info

Publication number: WO2011012054A1
Application number: PCT/CN2010/075255
Authority: WO
Inventors: Hai Li; Kunping Xu; Yun Yang; Wei FENG
Original assignee: Byd Company Limited
Priority date: 2009-07-29
Filing date: 2010-07-19
Publication date: 2011-02-03
Also published as: EP2460156A4; EP2460156A1; CN101986386A; CN101986386B; JP2012512434A; US20110026733A1

Abstract

A method for eliminating background noise may comprise a) detecting a characteristic value of an audio signal to obtain a characteristic signal reflecting a change trend of the audio signal; b) multiplying the characteristic signal and the audio signal to obtain a product signal; and c) 5 amplifying the product signal proportionally and outputting the amplified product signal. A device for eliminating background noise is also disclosed.

Description

METHOD AND DEVICE FOR ELIMINATING BACKGROUND NOISE CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority and benefits of Chinese Patent Application Serial No. 200910109073.3, filed with the State Intellectual Property Office of P. R. China on July 29, 2009, the entire content of which is incorporated herein by reference.

BACKGROUND TECHNICAL FIELD

The present invention relates to voice communication field, more particularly, to method and device for eliminating background noise.

DESCRIPTION OF THE RELATED ART

In voice communication, due to the complex environment where the caller is situated, in addition to the voice signal generated by the caller, the audio signal collected by the audio device may include a noise signal generated from other sound sources around the caller, such as voices of other people and sounds generated from vehicles. The noise signal affects the communication quality disadvantageously, so that more and more attentions are paid to the noise eliminating technology employing fewer components while maintaining high noise eliminating efficiency.

The conventional noise eliminating method comprises setting a noise threshold in, identifying a signal as a voice signal when the effective value of the signal is larger than the noise threshold, and as a noise signal when the effective value is smaller than the noise threshold, eliminating the noise signal, and amplifying the voice signal. Actually, at the beginning or end of the communication, the effective values of some voice signals may be smaller than the noise threshold, so that some voice signals will be lost, and the continuity of the voice can not be ensured. A new burst noise may be introduced during processing the noise and the fidelity of the voice signal is reduced. Furthermore, if the intensity of the noise varies significantly, the conventional noise eliminating method may not inhibit the noise effectively. SUMMARY

The present invention is directed to solve at least one of the problems exiting in the prior art. Accordingly, method and device for eliminating background noise are provided.

According to embodiments of an aspect of the present invention, there is provided a method for eliminating background noise, comprising steps of: a) detecting a characteristic value of an audio signal to obtain a characteristic signal reflecting a change trend of the audio signal; b) multiplying the characteristic signal and the audio signal to obtain a product signal; and c) amplifying the product signal proportionally and outputting the amplified product signal.

According to embodiments of another aspect of the present invention, there is provided a device for eliminating background noise, comprising: a characteristic value detecting unit, configured to receive an audio signal and detect a characteristic value of the audio signal to obtain a characteristic signal reflecting a change trend of the audio signal; a multiplying unit, coupled to the characteristic value detecting unit and configured to multiply the characteristic signal and the audio signal to obtain a product signal; and an amplifying unit, coupled to the multiplying unit and configured to amplify the product signal proportionally and output the amplified product signal .

According to embodiments of the present invention, the characteristic value of the audio signal is detected to obtain a characteristic signal reflecting a change trend of the audio signal, and the characteristic signal and the audio signal are multiplied to obtain a product signal, so that the voice signal and the noise signal may be separated effectively. The product signal is amplified proportionally, thus removing the environmental noise and enhancing the voice effectively.

The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The Figures and the detailed description which follow more particularly exemplify illustrative embodiments.

Additional aspects and advantages of the embodiments of present invention will be given in part in the following descriptions, become apparent in part from the following descriptions, or be learned from the practice of the embodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will become apparent and more readily appreciated from the following descriptions taken in conjunction with the drawings in which:

Fig. 1 is a flowchart of the method for eliminating background noise according to an embodiment of the present invention;

Fig. 2 is a block diagram of the device for eliminating background noise according to an embodiment of the present invention;

Fig. 3 A is a block diagram of the device for eliminating background noise according to another embodiment of the present invention;

Fig. 3B is a block diagram of the device for eliminating background noise according to yet another embodiment of the present invention;

Fig. 4 is a schematic circuit diagram of the audio collecting unit according to an embodiment of the present invention; Fig. 5 is a schematic circuit diagram of the pre- amplifying unit according to an embodiment of the present invention;

Fig. 6 is a schematic circuit diagram of the characteristic value detecting unit according to an embodiment of the present invention;

Fig. 7 is a schematic circuit diagram of the peak inhibition unit according to an embodiment of the present invention;

Fig. 8 is a schematic circuit diagram of the multiplying unit according to an embodiment of the present invention; and

Fig. 9 is a schematic circuit diagram of the amplifying unit according to an embodiment of the present invention.

DETAILED DESCRIPTION

Reference will be made in detail to embodiments of the present invention. The embodiments described herein with reference to drawings are explanatory, illustrative, and used to generally understand the present invention. The embodiments shall not be construed to limit the present invention. The same or similar elements and the elements having same or similar functions are denoted by like reference numerals throughout the descriptions.

The method for eliminating background noise according to an embodiment of the present will be described with reference to the drawings hereinafter.

As shown in Fig. 1, in an embodiment of the present invention, the method for eliminating background noise comprises: a) detecting a characteristic value of an audio signal to obtain a characteristic signal reflecting a change trend of the audio signal; b) multiplying the characteristic signal and the audio signal to obtain a product signal; and c) amplifying the product signal proportionally and outputting the amplified product signal.

After the characteristic value is detected for the audio signal to obtain the characteristic signal, the voice signal in the characteristic signal corresponds to a larger characteristic value signal and the noise signal in the characteristic signal corresponds to a smaller characteristic value. For example, in a 85 dB noise environment for a call, the average characteristic value of speech signal is about 10 ~ 30mv, the average characteristic value of noise signal is below 5mv. During multiplying the characteristic signal and the audio signal, the product of the voice signal and its characteristic signal is larger than that of the noise and its characteristic signal. The larger the voice signal is, the larger the product of the voice signal and its characteristic signal is, and the smaller the noise signal is, the smaller the product of the noise signal and its characteristic signal is. After the multiplication treatment, the difference value between the product of the voice signal and its characteristic signal, and the product of the noise signal and its characteristic signal, is larger than that between the voice signal and the noise signal in the original audio signal. Therefore, the noise will be separated from the voice signal to a greater extent.

In an embodiment of the present invention, the audio signal may be an audio signal collected from external environment or an audio signal transmitted from other devices. To improve the processing accuracy of the post circuits, in some embodiments of the present invention, the audio signal is a pre-amplified audio signal. In an embodiment of the present invention, the peak inhibition is performed for the characteristic signal before step b). Therefore, the product signal is obtained by multiplying the characteristic signal after peak inhibition and the audio signal.

Through the peak inhibition, in the b) the audio signal multiplies a fixed value in a predetermined range during multiplying, and is amplified in the same proportion, thus reducing the distortion resulted from different amplification proportions of the product signal. The peak inhibition may limit the magnification factor of the product signal into a predetermined range, thus avoiding a too large output signal.

In another embodiment of the present invention, step a) comprises detecting an effective value of the audio signal to obtain an average power signal of the audio signal, and the product signal is obtained by multiplying the average power signal and the audio signal. In step c), the proportional magnification factor is determined based on the magnification factor in the pre-amplifying and the attenuation degree of the noise signal, and generally, the proportional magnification factor is smaller than 1.

In yet another embodiment of the present invention, step a) comprises detecting a peak value of the audio signal to obtain a peak change signal reflecting a change trend of the peak value of the audio signal, and the product signal is obtained by multiplying the peak change signal and the audio signal. In step c), the proportional magnification factor is determined based on the magnification factor in the pre-amplifying and the attenuation degree of the noise signal, and generally, the proportional magnification factor is smaller than 1.

The device for eliminating background noise according to an embodiment of the present will be described below.

Referring to Fig. 2, in an embodiment of the present invention, the device for eliminating background noise comprises a characteristic value detecting unit 202, a multiplying unit 204, and an amplifying unit 206.

The characteristic value detecting unit 202 receives an audio signal and detects a characteristic value of the audio signal to obtain a characteristic signal reflecting a change trend of the audio signal.

The multiplying unit 204 is coupled to the characteristic value detecting unit 202 and multiplies the characteristic signal and the audio signal to obtain a product signal.

The amplifying unit 206 is coupled to the multiplying unit 204 and amplifies the product signal proportionally and output the amplified product signal. Referring to Fig. 3 A, in another embodiment of the present invention, the device for eliminating background noise comprises an audio collecting unit 208, the characteristic value detecting unit 202, the multiplying unit 204 and the amplifying unit 206. An output terminal of the audio collecting unit 208 is coupled to the input terminal of the characteristic value detecting unit 202 and a first input terminal of the multiplying unit 204 respectively. The output terminal of the characteristic value detecting unit 202 is coupled to a second input terminal of the multiplying unit 204, and the output terminal of the multiplying unit 204 is coupled to the input terminal of the amplifying unit 206. In some examples according to the present invention, the characteristic value detecting unit 202 is an effective value detecting unit. In some examples of the present invention, the characteristic value detecting unit 202 is a peak detecting unit.

As shown in Fig. 3A, the audio collecting unit 208 collects an audio signal and converts it into an audio signal, and then the audio signal is output to the characteristic value detecting unit 202 and the multiplying unit 204 respectively. The characteristic value detecting unit 202 detects the characteristic value of the audio signal to obtain a characteristic signal which reflects a change trend of the audio signal and is output to the multiplying unit 204. The multiplying unit 204 multiplies the characteristic signal and the audio signal to obtain a product signal. Finally, the amplifying unit 206 amplifies the product signal proportionally and outputs the amplified product signal.

Referring to Fig. 3B, in yet another embodiment of the present invention, the device for eliminating background noise comprises the audio collecting unit 208, a pre- amplifying unit 210, the characteristic value detecting unit 202, a peak inhibition unit 212, the multiplying unit 204 and the amplifying unit 206.

An output terminal of the audio collecting unit 208 is coupled to an input terminal of the pre-amplifying unit 210. An output terminal of the pre- amplifying unit 210 is coupled to the input terminal of the characteristic value detecting unit 202 and a first input terminal of the multiplying unit 204 respectively. The output terminal of the characteristic value detecting unit 202 is coupled to the input terminal of the peak inhibition unit 212. The output terminal of the peak inhibition unit 212 is coupled to a second input terminal of the multiplying unit 204, and the output terminal of the multiplying unit 204 is coupled to the input terminal of the amplifying unit 206. In some examples of the present invention, the characteristic value detecting unit 202 is an effective value detecting unit. Alternatively, the characteristic value detecting unit 202 is a peak value detecting unit.

As shown in Fig. 3B, the audio collecting unit 208 collects an audio signal and converts the audio signal into an audio signal which is received and pre-amplified by the pre-amplifying unit 210. The pre-amplified audio signal is output to the characteristic value detecting unit 202 and the multiplying unit 204 respectively. The characteristic value detecting unit 202 detects a characteristic value for the pre-amplified audio signal to obtain a characteristic signal which reflects a change trend of the audio signal and is output to the peak inhibition unit 212. The peak inhibition unit 212 performs peak inhibition for the characteristic signal and outputs the peak- inhibited characteristic signal to the multiplying unit 204. The multiplying unit 204 multiplies the characteristic signal and the pre-amplified audio signal to obtain a product signal, and the amplifying unit 206 amplifies the product signal proportionally and output the amplified product signal.

As shown in Fig. 4, the audio collecting unit 208 comprises a first bias resistor Rl, a microphone Ia, a blocking capacitor Cl and a follower. The follower comprises a second resistor R2, a third resistor R3, and a first operational amplifier Ul. One terminal of the resistor Rl is coupled to the common-mode voltage VCM, and another terminal of the resistor Rl is coupled to a terminal of the microphone Ia and a terminal of the blocking capacitor Cl respectively. Another terminal of the blocking capacitor Cl is coupled to one terminal of the resistor R2. Another terminal of the resistor R2 and a terminal of resistor R3 are coupled to the negative input terminal of the operational amplifier Ul. The positive input terminal of the operational amplifier Ul is coupled to the common-mode voltage VCM. Another terminal of resistor R3 is coupled to the output terminal of the operational amplifier Ul. The audio signal collected by the microphone Ia passes the blocking capacitor Cl to remove the bias voltage in the audio signal, thus forming an AC signal. The AC signal is input to the follower and output from the follower, the output signal is the audio signal ®.

Referring to Fig. 5, the pre- amplifying unit 210 comprises a forth resistor R4, a fifth resistor R5 and a second operational amplifier U2. One terminal of the forth resistor R4 and one terminal of the fifth resistor R5 are coupled to the negative input terminal of the operational amplifier U2. The positive input terminal of the operational amplifier U2 is coupled to a common-mode voltage VCM. Another terminal of resistor R5 is coupled to the output terminal of the operational amplifier U2. The audio signal ® is amplified predetermined times (generally 4-5 times) by the pre-amplifying unit 210 to obtain a pre-amplified audio signal (D. Pre-amplifying the audio signal ® helps increasing the processing accuracy of the post circuits.

As shown in Fig. 6, the characteristic value detecting unit 202 comprises a full wave rectifier (FWR) and a filter capacitor C2. The characteristic value detecting unit is an effective value detecting unit or a peak detecting unit. The pre-amplified audio signal (D received by the effective value detecting unit or the peak detecting unit 2 is rectified by the full wave rectifier (FWR) and filtered by the filter capacitor C2 to obtain an average power signal or a peak change signal ©of the amplified audio signal.

Referring to Fig. 7, the peak inhibition unit 212 comprises a comparator U3 and a selector switch Sl. The negative terminal of the comparator U3 is coupled to a first terminal of a predetermined peak inhibition voltage VF and adapted to be coupled to a terminal of the selector switch Sl. The positive terminal of the comparator U3 is adapted to be coupled to a second terminal of the selector switch Sl. The output terminal of the comparator U3 is coupled to a third terminal of the selector switch Sl. The comparator U3 compares the voltage of the average power signal or the peak change signal (D with the predetermined peak inhibition voltage VF. When the voltage of the voltage of the average power signal or the peak change signal (D is larger than the predetermined peak inhibition voltage VF, the selector switch Sl is selected to couple to the predetermined peak inhibition voltage VF and output it; otherwise the selector switch Sl selects the voltage of the average power signal or the peak change signal (D and output it, thus peak- inhibiting the voltage of the average power signal or the peak change signal (D. Therefore, the audio signal multiplies a fixed value in a predetermined range during multiplying, and is amplified in the same proportion, thus reducing the distortion resulted from the different amplification proportions of the audio signal. The peak inhibition may limit the magnification factor of the product signal into a predetermined range, thus avoiding a too large output signal.

Referring to Fig. 8, the multiplying unit 204 comprises a multiplier U4. The first input terminal of the multiplier U4 is coupled to the output terminal of the pre- amplifying unit 210 and the second input terminal of the multiplier U4 is coupled to the output terminal of the peak inhibition unit 212. The formula of the multiplier U4 is Z=KxXxY, where K is an inherent factor, X is the pre-amplified audio signal (D, Y is the average power signal or the peak change signal (D, and Z is a product signal @. The multiplying unit 204 multiplies the average power signal or the peak change signal (D and the pre-amplified audio signal so as to output the product signal @.

As shown in Fig. 9, the amplifying unit 206 comprises a fifth operational amplifier U5, an adjustable resistor R6, a seventh resistor R7, an eighth resistor R8, and a second switch S2. The positive input terminal of the fifth operational amplifier U5 is coupled to the common mode voltage VCM. The negative input terminal of the fifth operational amplifier U5 is coupled to a terminal of the resistor R6 and a terminal of the resistor R7. Another terminal of the resistor R6 is coupled to the output terminal of the multiplying unit 204. The second switch S2 is coupled to the mode control signal (MC). The mode control signal MC is controlled to select a suitable noise reduction mode by a command according to the intensity of the noise. According to some embodiments, the mode control signal MC is controlled manually. In a normal noise reduction mode, the switch S2 is controlled to open by the mode control signal MC, and the proportional factor of the amplifying unit is Al, the calculation formula of which is A1=(R7+R8)/R6. In a strong noise reduction mode, the switch S2 is controlled to close by the mode control signal MC, and the proportional factor of the amplifying unit is A2, the calculation formula of which is A2=R7/R6. The difference between the normal noise reduction mode and the strong noise reduction mode may be achieved by selecting a suitable resistor R8. After effectively separating the voice signal from the noise signal by the characteristic value detecting unit 202, a proportional factor in the amplifying unit 206 is set to determine a dividing point between the output signal being amplified with respect to the original input signal and the output signal being reduced with respect to the original input signal. The amplifying unit 206 receives the product signal @. When the value of the product signal is higher than the dividing point, the product signal is amplified by the amplifying unit 206. Otherwise, the product signal is reduced by the amplifying unit 206. The larger the difference between the value of the product signal and the dividing point is, the larger the magnified or reduced degree of the product signal is. The proportional factor is set according to the attenuation degree of the noise and the amplification degree of the voice signal. In the amplifying unit 206, because the value of the noise signal processed through the above procedure is lower than the dividing point, the noise is reduced; and because the value of the voice signal processed through the above procedure is higher than the dividing point, the voice signal is amplified, thus eliminating the noise signal and amplifying the voice signal.

Reference throughout this specification to "an embodiment," "some embodiments," "one embodiment", "an example," "a specific examples," or "some examples," means 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 the invention. Thus, the appearances of the phrases such as "in some embodiments," "in one embodiment" "in an embodiment", "an example," "a specific examples," or "some examples," in various places throughout this specification are not necessarily referring to the same embodiment or example of the invention. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

Although explanatory embodiments have been shown and described, it would be appreciated by those skilled in the art that changes, alternatives, and modifications can be made in the embodiments without departing from spirit and principles of the invention. Such changes, alternatives, and modifications all fall into the scope of the claims and their equivalents.

Claims

What is claimed is:

1. A method for eliminating background noise, comprising steps of:

detecting a characteristic value of an audio signal to obtain a characteristic signal reflecting a change trend of the audio signal;

multiplying the characteristic signal and the audio signal to obtain a product signal; and amplifying the product signal proportionally and outputting the amplified product signal.

2. The method of claim 1, wherein the audio signal is a pre-amplified audio signal.

3. The method of claim 1, further comprising performing peak inhibition for the characteristic signal.

4. The method of claim 3, wherein the product signal is obtained by multiplying the characteristic signal after peak inhibition and the audio signal.

5. The method of claim 1, wherein step a) comprises detecting an effective value of the audio signal to obtain an average power signal of the audio signal.

6. The method of claim 5, wherein the product signal is obtained by multiplying the average power signal and the audio signal.

7. The method of claim 1, wherein step a) comprises detecting a peak value of the audio signal to obtain a peak change signal reflecting a change trend of the peak value of the audio signal.

8. The method of claim 7, wherein the product signal is obtained by multiplying the peak change signal and the audio signal.

9. A device for eliminating background noise, comprising:

a characteristic value detecting unit, configured to receive an audio signal and detect a characteristic value of the audio signal to obtain a characteristic signal reflecting a change trend of the audio signal;

a multiplying unit, coupled to the characteristic value detecting unit and configured to multiply the characteristic signal and the audio signal to obtain a product signal; and

an amplifying unit, coupled to the multiplying unit and configured to amplify the product signal proportionally and output the amplified product signal.

10. The device of claim 9, wherein the audio signal is a pre-amplified audio signal.

11. The device of claim 9, further comprising a peak inhibition unit configured to receive the characteristic signal and perform peak inhibition for the characteristic signal.

12. The device of claim 11, wherein the multiplying unit multiplies the peak-inhibited characteristic signal and the audio signal.

13. The device of claim 9, wherein the characteristic value detecting unit comprises an effective value detecting unit configured to detect an effective value of the audio signal to obtain an average power signal of the audio signal.

14. The device of claim 13, wherein the product signal is obtained by multiplying the average power signal and the audio signal.

15. The device of claim 9, wherein the characteristic value detecting unit comprises a peak detecting unit configured to detect a peak value of the audio signal to obtain a peak change signal reflecting a change trend of the peak value of the audio signal.

16. The device of claim 15, wherein the product signal is obtained by multiplying the peak change signal and the audio signal.