Method and Device for Noise Reduction Control Using Microphone Array

• US 20120197638A1
• Filed: 12/15/2010
• Published: 08/02/2012
• Est. Priority Date: 12/28/2009
• Status: Active Grant

• Current Assignee: Weifang Goertek Microelectronics Co., Ltd. (Goertek Incorporated)
• Original Assignee: Goertek Incorporated
• Inventors: Lou, Shasha, Li, Bo, Li, Song
• Granted Patent: US 8,942,976 B2
• Time in Patent Office: Days
• US Class Current: 704/226
• CPC Class Codes: G10L 2021/02166 Microphone arrays; Beamforming
• CPC Class Codes: G10L 21/0208 Noise filtering

Abstract

The present invention provides a noise reduction control method using a microphone array and a noise reduction control device using a microphone array wherein the method comprises the steps of: S1: collecting, by the microphone array, acoustic signals; S2: estimating incidence angles of all acoustic signals of the microphone array; S3: conducting a statistics on signal components according to incidence angles; S4: determining a parameter α from a ratio of noise components according to the statistical result and using the parameter α as a control parameter for controlling an adaptive filter. With the present invention, space position information of the sound is obtained directly with the microphone array to control update of the adaptive filter more accurately, so as to eliminate noise, enhance SNR and protect speech quality well at the same time.

Claims

1. A noise reduction method using a microphone array, characterized by comprising steps of:

S1;

collecting, by the microphone array, acoustic signals;

S2;

estimating incidence angles of all acoustic signals collected by the microphone array;

S3;

conducting a statistics on signal components according to the incidence angles;

S4;

determining a parameter α

from a ratio of noise components according to the statistical result and using the parameter α

as a control parameter for controlling an adaptive filter.

2. A noise reduction method using a microphone array of claim 1, said step of determining incidence angles of sounds comprises:

S201;

conducting frequency domain transformation or sub-band transformation on the acoustic signals;

S202;

calculating phase differences of each frequency bins or sub-bands of the signals collected by the microphone array and calculating relative time delays of each of the frequency bins or sub-bands of signals of the microphone array based on the phase differences;

S203;

calculating incidence angles of signals collected by the microphone array based on the relative time delays of each of the frequency bins or sub-bands.

3. A noise reduction method using a microphone array of claim 1 or 2, characterized in that in step S4, specifically,

the adaptive filter is updated fast when there are only noises;

and the adaptive filter is updated slow when there is any target signal.

4. A noise reduction method using a microphone array of claim 3, characterized in that,

the smaller α

is, the slower the adaptive filter is updated;

in as case where α

is 0, the acoustic signal is all of target speech signal, and the adaptive filter is not updated;

in contrast, in a case where α

is 1, the acoustic signal is all of noise signal and the adaptive filter is updated at a fastest speed.

5. A noise reduction method using a microphone array of claim 4, characterized in that after step S2, it further comprises:

setting an angle transition range, dividing an entire space into several areas, calculating a parameter β

according to an area in which said incidence angle is located and taking β

*α

as the control parameter of the adaptive filter.

6. A noise reduction method using a microphone array of claim 5, characterized in that,

the entire space is divided into a protection area, a transition area and a suppression area, wherein, β

=0 for incidence angles within the protection area;

0<

β

<

1 for incidence angle angles within the transition area and β

=1 for incidence angles within the suppression area.

7. A noise reduction method using a microphone array of claim 2, characterized in that said step of converting acoustic signals into frequency domain further comprises:

S2011;

subjecting acoustic signals to framing;

S2012;

applying a window function to each frame of signal after framing;

S2013;

transforming windowed data into frequency domain by using DFT.

8. A noise reduction method using a microphone array of claim 7, characterized in that in step S2011,

an acoustic signal s_i is subjected to framing (i=1, 2), with N sample points in each frame or a frame size of 10 ms˜

32 ms, letting a m^th frame of signal is d_i(m,n), wherein 0≦

n<

N, 0≦

m;

there are M overlapping sample points between two adjacent frames, with L=N−

M sample points of new data for each frame;

the m^th frame of data is d_i(m,n)=s_i(m*L+n).

9. A noise reduction method using a microphone array of claim 8, characterized in that

assuming N=256, and overlapping number M=128˜

192.

10. A noise reduction device using a microphone array, comprising:

a microphone array for collecting acoustic signals;

a filtering control unit for determining incidence angles of all acoustic signals collected by the microphone array, conducting a statistics on signal components based on the incidence angles and then determining a parameter α

from a ratio of noise components according to the statistical result and using the parameter α

as a control parameter for controlling an adaptive filter;

an adaptive filter for filtering out noises.

11. A noise reduction device using a microphone array of claim 10, characterized in that said filtering control unit comprises:

a DFT unit for discrete Fourier transforming acoustic signals into frequency domain;

a signal delay estimation unit for calculating phase differences of each frequency bins or sub-bands of the signals collected by the microphone array and calculating relative time delays of each frequency bins or sub-bands of the signals collected by the microphone array based on the phase differences;

a signal direction estimation unit for calculating incidence angles of the signals collected by the microphone array based on the relative time delays of each frequency bins or sub-bands;

a signal component statistics unit for conducting a statistics on components of target signal based on said incidence angles and distinguishing them to find out a target signal component and noise component, and determining a parameter α

from a ratio of noise components according to the statistical result and using the parameter α

as a control parameter for controlling the adaptive filter.

12. A noise reduction device using a microphone array of claim 11, characterized in that said DFT unit comprises:

a framing unit for framing the acoustic signals;

a window function unit for applying a window function to each frame of signal after framing;

a DFT converting unit for transforming windowed data into frequency domain.

13. A noise reduction device using a microphone array of any one of claims 10-13, characterized in that said microphone array is completely comprised of omnidirectional microphones or comprised of omnidirectional microphones and monodirectional microphones or completely comprised of monodirectional microphones.

14. A noise reduction device using a microphone array of claim 11, characterized in that said signal component statistics unit is further configured for dividing an entire space into several areas, calculating a parameter β

according to an area in which said incidence angle is located, and taking β

*α

as the control parameter of the adaptive filter.