SIGNAL PROCESSING APPARATUS, MICROPHONE ARRAY DEVICE, AND STORAGE MEDIUM STORING SIGNAL PROCESSING PROGRAM

• US 20110158426A1
• Filed: 12/23/2010
• Published: 06/30/2011
• Est. Priority Date: 12/28/2009
• Status: Abandoned Application

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: MATSUO, Naoshi
• Application Number:
  US12/977,341
• Publication Number:
  US 20110158426A1
• Time in Patent Office: Days
• US Class Current: 381/92
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

A signal processing apparatus includes: two sound input units, an orthogonal transformer to transform two sound signals input from the two sound input units into respective spectral signals in a frequency domain, a phase difference calculator to calculate a phase difference between the spectral signals in the frequency domain, a range determiner to determine a coefficient responsive to a frequency in the phase difference as a function of frequency, and determine a suppression range related to a phase on a per frequency basis of the frequency responsive to the coefficient; and a filter to phase-shift a component of one of the spectral signals on a per frequency basis in order to generate a phase-shifted spectral signal when the phase difference at each frequency falls within the suppression range, synthesizing the phase-shifted spectral signal and the other of the spectral signals in order to generate a filtered spectral signal.

Claims

1. A signal processing apparatus, comprising:

at least two sound input units;

an orthogonal transformer to transform two sound signals, out of sound signals in a time domain input from the at least two sound input units, into respective spectral signals in a frequency domain;

a phase difference calculator to calculate a phase difference between the spectral signals in the frequency domain;

a range determiner to determine a coefficient responsive to a frequency in the phase difference as a function of frequency, and determine a suppression range related to a phase on a per frequency basis of the frequency responsive to the coefficient; and

a filter to phase-shift a component of a first of the spectral signals on a per frequency basis in order to generate a phase-shifted spectral signal when the phase difference at each frequency falls within the suppression range, synthesizing the phase-shifted spectral signal and a second of the spectral signals in order to generate a filtered spectral signal.

2. The signal processing apparatus according to claim 1, wherein the range determiner determines the suppression range based on the coefficient of the phase difference, and

wherein the phase difference is within a reception range related to the phase at each frequency prior to the determination of the suppression range.

3. The signal processing apparatus according to claim 1, wherein the range determiner determines based on the coefficient a narrower than a first reception range such that a noise suppression quantity becomes constant, based on the coefficient of the phase difference, and

wherein the phase difference is within the first reception range related to the phase at each frequency prior to the determination of the suppression range.

4. The signal processing apparatus according to claim 1, wherein the range determiner estimates a noise spectrum of the two spectral signals, and determines the coefficient of the phase difference related to the frequency of the two spectral signals having a power higher than a power of the noise spectrum estimated.

5. The signal processing apparatus according to claim 1, wherein the range determiner determines as a statistical mean value the coefficient of the phase difference by statistically processing a plurality of phase differences for different frequencies.

6. The signal processing apparatus according to claim 1, wherein the range determiner tentatively determines at least first and second suppression ranges respectively corresponding to at least first and second coefficients as the coefficients, determines a first power of a first filtered spectral signal as the filtered spectral signal when the phase difference on a specific frequency falls within the first suppression range, and a second power of a second filtered spectral signal as the filtered spectral signal when the phase difference on the specific frequency falls within the second suppression range, and compares the first power with the second power and selects the first suppression range or the second suppression range respectively corresponding to the first power or the second power, whichever is higher, and

wherein the filter generates the filtered spectral signal with the phase difference falling within the selected suppression range.

7. A microphone array device, comprising:

at least two microphones;

an orthogonal transformer to transform two sound signals, out of the sound signals in a time domain input from the at least two microphones, into respective spectral signals in a frequency domain;

a phase difference calculator to calculate a phase difference between the spectral signals in the frequency domain;

a range determiner to determine a coefficient responsive to a frequency in the phase difference as a function of frequency, and determining a suppression range related to a phase on a per frequency basis of the frequency responsive to the coefficient;

a filter to phase-shift a component of a first of the spectral signals on a per frequency basis in order to generate a phase-shifted spectral signal when the phase difference at each frequency falls within the suppression range, synthesizing the phase-shifted spectral signal and a second of the spectral signals in order to generate a filtered spectral signal; and

an inverse-orthogonal transformer to inverse-transform the filtered spectral signal into a sound signal in the time domain.

8. A non-transitory computer-readable medium for recording a signal processing program allowing a computer to execute an operation, comprising:

transforming two sound signals, out of sound signals in a time domain input from at least two sound input units, into respective spectral signals in a frequency domain;

calculating a phase difference between the spectral signals in the frequency domain;

determining a suppression range related to a phase on a per frequency basis of the frequency responsive to a coefficient of the frequency in the phase difference as a function of frequency;

phase-shifting a component of a first of the spectral signals on a per frequency basis in order to generate a phase-shifted spectral signal when the phase difference at each frequency falls within the suppression range, synthesizing the phase-shifted spectral signal and a second of the spectral signals in order to generate a filtered spectral signal.

9. The computer-readable medium according to claim 8, wherein the determining determines the suppression range based on the coefficient of the phase difference, and

wherein the phase difference is within a reception range related to the phase at each frequency prior to the determination of the suppression range.

10. The computer-readable medium according to claim 8, wherein the determining determines based on the coefficient and a narrower than a first reception range such that a noise suppression quantity becomes constant, based on the coefficient of the phase difference, and

wherein the phase difference is within the first reception range related to the phase at each frequency prior to the determination of the suppression range.

11. The computer-readable medium according to claim 8, wherein the determining estimates a noise spectrum of the spectral signals, and determines the coefficient of the phase difference related to the frequency of the spectral signals having a power higher than a power of the noise spectrum estimated.

12. The computer-readable medium according to claim 8, wherein the determining determines as a statistical mean value the coefficient of the phase difference by processing a plurality of phase differences for different frequencies.

13. The computer-readable medium according to claim 8, wherein the determining tentatively determines at least first and second suppression ranges respectively corresponding to at least first and second coefficients as the coefficients, determines a first power of a first filtered spectral signal as the filtered spectral signal when the phase difference on a specific frequency falls within the first suppression range, and a second power of a second filtered spectral signal as the filtered spectral signal when the phase difference on the specific frequency falls within the second suppression range, and compares the first power with the second power and selects the first suppression range or the second suppression range respectively corresponding to the first power or the second power, whichever is higher, and

wherein the filter generates the filtered spectral signal with the phase difference falling within the selected suppression range.