System for noise suppression, transceiver and method for noise suppression

• US 7,035,796 B1
• Filed: 05/06/2000
• Issued: 04/25/2006
• Est. Priority Date: 05/06/2000
• Status: Expired due to Fees

• Current Assignee: Nanyang Technology University
• Original Assignee: Nanyang Technology University
• Inventors: Zhang, Ming, Lan, Hui
• Primary Examiner(s): MCFADDEN, SUSAN IRIS
• Application Number:
  US10/275,460
• Time in Patent Office: 2,180 Days
• Field of Search: 704/500
• US Class Current: 704/226
• CPC Class Codes: G10L 2021/02085 Periodic noise
• CPC Class Codes: G10L 21/0208 Noise filtering

Abstract

A system with an accompanying method is provided to improve the signal-to-noise ratio (SNR) of noisy speech by suppressing acoustic background noise. The background noise consists of narrow band noise from rotating machine, audio signals from stereo-loudspeakers of audio entertainment device, and other ambient noise. In this system/apparatus, a microphone senses the speech intermingled with the background noise, and another microphone senses the noisy background. In addition, a measurement sensor is used to measure RPM (revolutions-per-minutes) of the rotating machine and two wires are used to acquire audio signals from the stereo-loudspeakers of the audio entertainment device. Furthermore, to provide better suppression performance for the acoustic audio signals, the characteristics of these loudspeakers are used to compensate for the distortion caused by the loudspeakers. Adaptive comb filters and adaptive FIR filters are applied to estimate the ambient noise and suppress the background noise. After processing, the system outputs the enhanced speech signal with higher SNR.

Claims

1. A System for noise suppression of a speech signal that is intermingled with general noise, said system comprising:

a) an Input Unit for receiving

(1) the speech signal intermingled with the general noise;

(2) at least one audio signal from an audio source;

said Input Unit comprising a Sound Processing Unit and a sensor for measuring a rotating rate of a device, in the course of which the Sound Processing Unit generates a second noise signal of the device using the rotating rate value measured by the sensor;

b) a Processing Unit comprising

(1) a first adaptive filter to produce a first noise signal from the audio signal;

(2) a first calculation means to remove the first noise signal from the speech signal, thereby producing a first noise suppressed speech signal from the speech signal;

(3) a second adaptive filter to produce a dynamically varying third noise signal from the second noise signal; and

(4) a second calculation means to remove the third noise signal from the first noise suppressed speech signal, thereby producing a second noise suppressed speech signal which is a desired speech signal with the first noise signal and the third noise signal suppressed from the speech signal received by said Input Unit.

2. The system as defined in claim 1,

wherein said Input Unit comprises

a) a converter to convert said audio signal into a digital audio signal;

b) a loudspeaker compensation unit that modifies the digital audio signal in such a way that a distortion of the loudspeaker, to which the audio signal is directed, is compensated.

3. The system as defined in claim 2,

wherein said audio signal is a stereo audio signal and for each channel a separate compensation unit and a separate adaptive filter is provided.

4. The system as defined in claim 2,

wherein said compensator is constructed to compensate the distortion of the loudspeaker by filtering the digital audio signal via the transfer function of the loudspeaker.

5. The system as defined in claim 4,

wherein said transfer function is evaluated offline.

6. The system as defined in claim 1,

wherein said Sound Processing Unit is a sine-wave generator.

7. The system as defined in claim 1,

wherein said device is a rotating device, particularly an engine.

8. The system as defined in claim 1,

wherein said sensor is a means to measure revolutions per minute of the device.

9. The system as defined in claim 1,

wherein said second adaptive filter is an adaptive comb filter.

10. A System for noise suppression of a speech signal that is intermingled with general noise, said system comprising:

a) an input device for receiving

(1) the speech signal intermingled with the general noise;

(2) at least one audio signal from an audio source;

b) a Processing Unit comprising

(1) a first adaptive filter to produce a first noise signal from the audio signal;

(2) a first calculation means to remove the first noise signal from the speech signal thereby producing a first noise suppressed speech signal from the speech signal;

(3) a second adaptive filter to produce a third noise signal from a second noise signal of a device; and

(4) a third calculation means to remove the third noise signal from the first noise suppressed speech signal, thereby producing a third noise suppressed speech signal with the third noise signal and the first noise signal suppressed from the speech signal received by said input device.

11. A method for noise suppression in a speech signal intermingled with general noise to be executed on a system as defined in claim 10.

12. The system as defined in claim 10,

wherein said Processing Unit comprises

a) an Ambient Noise Estimator comprising means to produce a fourth noise signal from said audio signal, the second noise signal and a background noise signal;

b) a fourth calculation means to remove the fourth noise signal from the third noise suppressed speech signal, thereby producing a fourth noise suppressed speech signal.

13. The system as defined in claim 12,

wherein said Processing Unit comprises a third adaptive filter that adjusts the fourth noise signal into a modified fourth noise signal.

14. The system as defined in claim 13,

wherein said Processing Unit comprises a voice detection unit that switches the second adaptive filter, the first adaptive filter and the third adaptive filter, if the speech signal intermingled with the general noise exceeds a predefined level.

15. The system as defined in claim 12,

wherein said Ambient Noise Estimator comprises:

a) a fourth adaptive filter that modifies the second noise signal into a fifth noise signal;

b) a fifth calculation means to remove the fifth noise signal from the background noise signal, thereby producing a sixth noise signal;

c) a fifth adaptive filter that modifies the audio signal into a seventh noise signal;

d) a sixth calculation means to remove the seventh noise signal from the sixth noise signal, thereby producing the fourth noise signal from the background noise signal.

16. The system as defined in claim 15,

wherein said Noise/Audio-Signal-Detector switches the fourth adaptive filter and the fifth adaptive filter.

17. The system as defined in claim 10,

wherein said Processing Unit comprises a Noise/Audio-Signal-Detector to switch the second adaptive filter if the sensor exceeds a first predefined value and to switch the first adaptive filter if the audio signal exceeds a second predefined value.

18. The system as defined in claim 17,

wherein the first predefined value is predefined in such a way that it is exceeded if there is noise from the device.

19. The system as defined in claim 17,

wherein the second predefined value is predefined in such a way that it is exceeded if there is noise from the audio source.

20. The system as defined in claim 10,

wherein at least one of the following filters is a FIR-filter:

said first adaptive filter, said third adaptive filter or said fifth adaptive filter.

21. The system as defined in claim 10,

wherein the third noise suppressed speech signal is converted into an analogue signal and transferred to an Output Unit.

22. The system as defined in claim 10,

wherein said system is a transceiver.