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

• US 9,736,287 B2
• Filed: 02/25/2013
• Issued: 08/15/2017
• Est. Priority Date: 02/25/2013
• Status: Active Grant

• Current Assignee: Spreadtrum Communications USA
• Original Assignee: Spreadtrum Communications USA
• Inventors: Jiang, Bin, Lin, Fuhuei, Wu, Sheng, Xu, Jingming
• Primary Examiner(s): Appiah, Charles
• Assistant Examiner(s): Mastrodonato, Margaret G
• Application Number:
  US14/344,133
• Publication Number:
  US 20150350395A1
• Time in Patent Office: 1,632 Days
• Field of Search: None
• CPC Class Codes: H04B 1/0014 using DSP [Digital Signal Processor] quadrature modulation and demodulation
• CPC Class Codes: H04M 1/03 Constructional features of telephone transmitters or receivers, e.g. telephone hand-sets
• CPC Class Codes: H04M 1/60 including speech amplifiers
• CPC Class Codes: H04R 2410/05 Noise reduction with a separate noise microphone
• CPC Class Codes: H04R 2499/11 Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407
• CPC Class Codes: H04W 88/02 Terminal devices

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.

Claims

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.