Signal processing apparatus and signal processing method

• US 8,638,952 B2
• Filed: 06/17/2010
• Issued: 01/28/2014
• Est. Priority Date: 06/23/2009
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Matsuo, Naoshi
• Primary Examiner(s): Nguyen, Duc
• Assistant Examiner(s): Le, Phan
• Application Number:
  US12/817,406
• Publication Number:
  US 20100322437A1
• Time in Patent Office: 1,321 Days
• Field of Search: 381/94.2, 381/86, 381/92
• US Class Current: 381/94.2
• CPC Class Codes: G10L 2021/02165 Two microphones, one receiving mainly the noise signal and the other one mainly the speech signal
• CPC Class Codes: G10L 21/0208 Noise filtering
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

There is provided a signal processing apparatus, for suppressing a noise, which includes a first calculator to obtain a phase difference between two spectrum signals in a frequency domain transformed from sound signals received by at least two microphones to estimate a sound source by the phase difference, a second calculator to obtain a value representing a target signal likelihood and to determine a sound suppressing phase difference range at each frequency, in which a sound signal is suppressed, on the basis of the target signal likelihood, and a filter. The filter generate a synchronized spectrum signal by synchronizing each frequency component of one of the two spectrum signals to each frequency component of the other of the two spectrum signals for each frequency when the phase difference is within the sound suppressing phase difference range and to generate a filtered spectrum signal.

Claims

1. A signal processing apparatus comprising:

a first calculator to obtain phase difference between two spectrum signals in a frequency domain transformed from sound signals received by at least two microphones for each frequency in a certain frequency band, each of the two spectrum signals including frequency components;

a second calculator to obtain, for each frequency component of one spectrum signal of the two spectrum signals, a value representing a target signal likelihood dependent on a value of the frequency component, and to determine whether the frequency component includes noise on the basis of the value representing the target signal likelihood obtained for the frequency component; and

a filter to, when the second calculator determines that a respective frequency component includes noise, generate a synchronized spectrum signal by synchronizing the respective frequency component of one of the two spectrum signals to the respective frequency component of the other of the two spectrum signals by phase shifting on the basis of the phase difference obtained by the first calculator, and to generate a filtered spectrum signal by subtracting the synchronized spectrum signal from the other of the two spectrum signals or adding the synchronized spectrum signal to the other of the two spectrum signals.

2. A signal processing apparatus for suppressing a noise comprising:

a first calculator to obtain a phase difference between two spectrum signals in a frequency domain transformed from sound signals received by at least two microphones and to estimate a sound source by the phase difference;

a second calculator to obtain a value representing a target signal likelihood and to determine a sound suppressing phase difference range at each frequency, in which a sound signal is suppressed, on the basis of the target signal likelihood; and

a filter to generate a synchronized spectrum signal by synchronizing each frequency component of one of the two spectrum signals to each frequency component of the other of the two spectrum signals for each frequency when the phase difference is within the sound suppressing phase difference range and to generate a filtered spectrum signal by subtracting the synchronized spectrum signal from the other of the two spectrum signals or adding the synchronized spectrum signal to the other of the two spectrum signals.

3. The signal processing apparatus according to claim 2, wherein the second calculator sets the phase difference range narrower and a sound receiving phase difference range wider, in which the noise is not suppressed in accordance with increase in the value representing the target signal likelihood.

4. The signal processing apparatus according to claim 2, further comprising a determiner to determine the value representing the target signal likelihood on the basis of an absolute value of an amplitude of one of the two spectrum signals or a square of the absolute value.

5. The signal processing apparatus according to claim 2, further comprising a determiner to determine the value representing the target signal likelihood on the basis of a ratio of a current absolute value of an amplitude of one of the two spectrum signals or a square of the current absolute value to a time average value of an absolute value of the amplitude or of a square of the absolute value.

6. The signal processing apparatus according to claim 2, further comprising a synchronization coefficient generator to receive a talker direction information and to set the sound suppressing phase difference range on the basis of the talker direction information, the talker direction information being corresponding to information of a direction toward the talker.

7. The signal processing apparatus according to claim 2, wherein the filter generates the filtered spectrum signal by subtracting a product of an adjusting coefficient and the synchronized spectrum signal from the other of the two spectrum signals, the adjusting coefficient being determined in accordance with the phase difference being within the sound suppressing phase difference range or not, the adjusting coefficient being adjusting a degree of a subtraction in accordance of the frequency.

8. The signal processing apparatus according to claim 2, further comprising a orthogonal transformer to transform at least two sound signals in a time domain into the two spectrum signals in a frequency domain, wherein the phase difference is corresponding to a sound arrival direction at an arrangement of the microphones, the target signal likelihood is a target sound signal likelihood, and the second calculator calculates each synchronization coefficient associated with each amount of phase shift for synchronizing each frequency component of one of the two spectrum signals to each frequency component of the other of the two spectrum signals for each frequency.

9. The signal processing apparatus according to claim 7, wherein the second calculator calculates, for each time frame, the synchronization coefficient based on a ratio of both of the two spectrum signals for each frequency when the phase difference is within the sound suppressing phase difference range.

10. The signal processing apparatus according to claim 3, further comprising a determiner to determine the value representing the target signal likelihood on the basis of an absolute value of an amplitude of one of the two spectrum signals or a square of the absolute value.

11. The signal processing apparatus according to claim 3, further comprising a determiner to determine the value representing the target signal likelihood on the basis of a ratio of a current absolute value of an amplitude of one of the two spectrum signals or a square of the current absolute value to a time average value of an absolute value of the amplitude or of a square of the absolute value.

12. The signal processing apparatus according to claim 3, further comprising a synchronization coefficient generator to receive a talker direction information and to set the sound suppressing phase difference range on the basis of the talker direction information, the talker direction information being corresponding to information of a direction toward the talker.

13. The signal processing apparatus according to claim 3, wherein the filter generates the filtered spectrum signal by subtracting a product of an adjusting coefficient and the synchronized spectrum signal from the other of the two spectrum signals, the adjusting coefficient being determined in accordance with the phase difference being within the sound suppressing phase difference range or not, the adjusting coefficient being adjusting a degree of a subtraction in accordance of the frequency.

14. The signal processing apparatus according to claim 3, further comprising a orthogonal transformer to transform at least two sound signals in a time domain into the two spectrum signals in a frequency domain, wherein the phase difference is corresponding to a sound arrival direction at an arrangement of the microphones, the target signal likelihood is a target sound signal likelihood, and the second calculator calculates each synchronization coefficient associated with each amount of phase shift for synchronizing each frequency component of one of the two spectrum signals to each frequency component of the other of the two spectrum signals for each frequency.

15. A signal processing method using two spectrum signals in a frequency domain transformed from sound signals received by at least two microphones, each of the two spectrum signals including frequency components, the method comprising:

obtaining a phase difference between the two spectrum signals for each frequency in a certain frequency band;

obtaining, for each frequency component of one spectrum signal of the two spectrum signals, a value representing a target signal likelihood dependent on a value of the frequency component;

determining, for each frequency component of said one spectrum signal of the two spectrum signals, whether the frequency component includes noise on the basis of the value representing the target signal likelihood obtained for the frequency component; and

when said determining determines that a respective frequency component includes noise,

generating a synchronized spectrum signal by synchronizing the respective frequency component of one of the spectrum signals to the respective frequency component of the other of the spectrum signals by phase shifting on the basis of the obtained phase difference, and

generating a filtered spectrum signal by subtracting the synchronized spectrum signal from the other of the spectrum signals or adding the synchronized spectrum signal to the other of the spectrum signals.