Detecting and switching between noise reduction modes in multi-microphone mobile devices

Patent metadata

Field	Value
Publication number	US-9736287-B2
Application number	US-201314344133-A
Country	US
Kind code	B2
Filing date	Feb 25, 2013
Priority date	Feb 25, 2013
Publication date	Aug 15, 2017
Grant date	Aug 15, 2017

Abstract

A method of switching between noise reduction modes in multi-microphone mobile devices may include receiving a first sound signal at a first sound receiver and receiving a second sound signal at a second sound receiver. The method may also include determining a first power value associated with the first sound signal and determining a second power value associated with the second sound signal. The method may additionally include comparing the first power value to the second power value and switching between a single-microphone noise reduction mode and a dual-microphone noise reduction mode based on the comparison.

First claim

What is claimed is:

1. A method of switching between noise reduction modes in multi-microphone mobile devices, the method comprising:
receiving a first sound signal at a first sound receiver;
receiving a second sound signal at a second sound receiver;
determining a first power value associated with the first sound signal comprising a power spectral density associated with the first sound signal;
determining a second power value associated with the second sound signal comprising a power spectral density associated with the second sound signal;
dividing the first sound signal into first discrete time frames;
comparing the first power value to the second power value; and
switching between a single-microphone noise reduction mode and a dual-microphone noise reduction mode based on the comparison;
wherein the switching between the single-microphone noise reduction mode and the dual-microphone noise reduction mode is further based on a comparison of a number of consecutive first discrete time frames during which voice activity is not detected to a selected value, and
wherein the power spectral density for each first and second sound signal is computed by a present frame's spectrum and a last frame's power spectral density.

2. The method of claim 1 wherein the first sound receiver is located away from the second sound receiver on a mobile device.

3. The method of claim 2 wherein the first sound receiver is located on a front side of the mobile device, and the second sound receiver is located on a back side of the mobile device.

4. The method of claim 1 further comprising:
determining that a difference between the first power level and the second power level is less than or equal to a threshold amount; and
switching to the single-microphone noise reduction mode.

5. The method of claim 1 further comprising:
determining that the first power level is greater than the second power level by at least a threshold amount; and
switching to the dual-microphone noise reduction mode.

6. The method of claim 1 further comprising:
dividing the second sound signal into second discrete time frames;
performing a Fourier transform on the first discrete time frames; and
performing a Fourier transform on the second discrete time frames.

7. The method of claim 1 wherein the step of comparing the first power value to the second power value comprises computing a mean normalized difference between the power spectral density associated with the first sound signal and the power spectral density associated with the second sound signal.

8. The method of claim 1 further comprising detecting voice activity in the first sound signal.

9. A multi-microphone mobile device that switches between noise reduction modes, the device comprising:
a first sound receiver structured to receive a first sound signal comprising a power spectral density associated with the first sound signal;
a second sound receiver structured to receive a second sound signal comprising a power spectral density associated with the second sound signal;
a signal processing module structured to:
determine a first power value associated with the first sound signal;
determine a second power value associated with the second sound signal;
divide the first sound signal into first discrete time frames; and
a noise reduction module structured to:
receive a comparison of the first power value and the second power value; and
switch between a single-microphone noise reduction mode and a dual-microphone noise reduction mode based on the comparison;

wherein the noise reduction module is structured such that switching between the single-microphone noise reduction mode and the dual-microphone noise reduction mode is further based on a comparison of a number of consecutive first discrete time frames during which voice activity is not detected to a selected value,
wherein the power spectral density for each first and second sound signal is computed by a present frame's spectrum and a last frame's power spectral density.

10. The device of claim 9 wherein the signal processing module and the noise reduction module are part of a Digital Signal Processing (DSP) chip.

11. The device of claim 9 wherein the multi-microphone mobile device comprises a smart phone.

12. The device of claim 9 wherein:
the signal processing module is further configured to determine that a difference between the first power level and the second power level is less than or equal to a threshold amount; and
the noise reduction module is further configured to switch to the single-microphone noise reduction mode.

13. The device of claim 9 wherein:
the signal processing module is further configured to determine that the first power level is greater than the second power level by at least a threshold amount; and
the noise reduction module is further configured to switch to the dual-microphone noise reduction mode.

14. The device of claim 9 wherein the signal processing module is further configured to:
divide the second sound signal into second discrete time frames;
perform a Fourier transform on the first discrete time frames; and
perform a Fourier transform on the second discrete time frames.

15. A non-transitory computer-readable medium on which is stored a sequence of instructions which, when executed by one or more processors, causes the one or more processors to perform:
receiving a first sound signal at a first sound receiver;
receiving a second sound signal at a second sound receiver;
determining a first power value associated with the first sound signal comprising a power spectral density associated with the first second signal;
determining a second power value associated with the second sound signal comprising a power spectral density associated with the second sound signal;
dividing the first sound signal into first discrete time frames;
comparing the first power value to the second power value; and
switching between a single-microphone noise reduction mode and a dual-microphone noise reduction mode based on the comparison; and
wherein the switching between the single-microphone noise reduction mode and the dual-microphone noise reduction mode is further based on a comparison of a number of consecutive first discrete time frames during which voice activity is not detected to a selected value, and
wherein the power spectral density for each first and second sound signal is computed by a present frame's spectrum and a last frame's power spectral density.

16. The computer-readable memory according to claim 15 , wherein the instructions further cause the one or more processors to switch between noise reduction modes in multi-microphone mobile devices by:
determining that a difference between the first power level and the second power level is less than or equal to a threshold amount; and
switching to the single-microphone noise reduction mode.

17. The computer-readable memory according to claim 15 , wherein the instructions further cause the one or more processors to switch between noise reduction modes in multi-microphone mobile devices by:
determining that the first power level is greater than the second power level by at least a threshold amount; and
switching to the dual-microphone noise reduction mode.

Assignees

• Spreadtrum Comm Shanghai Co

Inventors

• Jiang Bin
• Wu Sheng
• Lin Fuhuei
• Xu Jingming

Classifications

• H04W88/02

  Terminal devices · CPC title

• H04R2410/05

  Noise reduction with a separate noise microphone · CPC title

• H04M1/03

  Constructional features of telephone transmitters or receivers, e.g. telephone hand-sets · CPC title

• H04M1/60 Primary

  including speech amplifiers · CPC title

• H04B1/0014

  using DSP [Digital Signal Processor] quadrature modulation and demodulation · CPC title