Method and noise suppression circuit incorporating a plurality of noise suppression techniques

1. A noise suppression circuit for use in an audio signal processing circuit, the noise suppression circuit comprising:

a plurality of different types of noise activity detectors including a babble noise activity detector and a stationary noise activity detector, where each noise activity detector is adapted for detecting the presence of a different type of noise in a received signal; and

a plurality of different types of noise reduction circuits including a noise attenuation circuit and a noise subtraction circuit, where each noise reduction circuit is adapted for removing a different type of detected noise, where each noise reduction circuit respectively corresponds to one of the plurality of noise activity detectors with the noise attenuation circuit corresponding to the stationary noise detector and the noise subtraction circuit corresponding to the babble noise activity detector;

wherein when each one of the plurality of noise activity detectors detects the presence of a corresponding type of noise in the received signal, the respective noise reduction circuit is selectively activated to condition the received signal to reduce the amount of the detected types of noise, and wherein the noise attenuation circuit and the noise subtraction circuit are both activated when both the stationary noise activity detector and the babble noise activity detector detect the presence of the corresponding noise types for the stationary noise activity detector and the babble noise activity detector in the received signal.

2. A noise suppression circuit in accordance with claim 1 , wherein the stationary noise activity detector includes a spectrum domain noise activity detector and a time domain noise activity detector.

3. A noise suppression circuit in accordance with claim 1 , wherein the babble noise activity detector includes a gaussian mixture model.

4. A noise suppression circuit in accordance with claim 3 , wherein the gaussian mixture model includes a speech model for detecting the presence of a desired voice signal, and a noise model for detecting the presence of babble noise.

5. A noise suppression circuit in accordance with claim 4 , wherein the detected voice signal and the detected babble noise are used to formulate a signal to be used for a corresponding one of the noise reduction circuits.

6. A noise suppression circuit in accordance with claim 4 , wherein the detected babble noise is used to update the noise model.

7. A noise suppression circuit in accordance with claim 1 further comprising a comfort noise source for producing a comfort noise signal, and a mixer for combining the comfort noise signal with the received signal, which has been conditioned to reduce the amount of the detected types of noise.

8. A noise suppression circuit in accordance with claim 1 , wherein the noise suppression circuit is incorporated in a two way communication device including a microphone and a speaker.

9. A noise suppression circuit in accordance with claim 8 further comprising an echo cancellation circuit for receiving a signal to be reproduced by the speaker and removing any speaker reproduced signal detected by the microphone.

10. A noise suppression circuit in accordance with claim 1 , wherein the noise suppression circuit is incorporated as part of a radio frequency telephone.

11. A two way communication device comprising: a transceiver for communicating with a remote radio source;

a speaker for reproducing an audio signal received from a remote radio source; a microphone for detecting an audio signal to be transmitted to the remote radio source; and

an audio signal processing circuit including a noise suppression circuit for conditioning the audio signal detected by the microphone prior to being transmitted to the remote radio source by the transceiver, the noise suppression circuit comprising

a plurality of different types of noise activity detectors including a babble noise activity detector and a stationary noise activity detector, where each noise activity detector is adapted for detecting the presence of a different type of noise in an audio signal detected by the microphone, and

a plurality of different types of noise reduction circuits including a noise attenuation circuit and a noise subtraction circuit, where each noise reduction circuit is adapted for removing a different type of detected noise, where each noise reduction circuit respectively corresponds to one of the plurality of noise activity detectors with the noise attenuation circuit corresponding to the stationary noise detector and the noise subtraction circuit corresponding to the babble noise activity detector;

wherein when each one of the plurality of noise activity detectors detects the presence of a corresponding type of noise in the audio signal detected by the microphone, the respective noise reduction circuit is selectively activated to condition the audio signal detected by the microphone to reduce the amount of the detected types of noise, and wherein the noise attenuation circuit and the noise subtraction circuit are both activated when both the stationary noise activity detector and the babble noise activity detector detect the presence of the corresponding noise types for the stationary noise activity detector and the babble noise activity detector in the audio signal.

12. A two way communication device in accordance with claim 11 wherein the noise suppression circuit further comprises a comfort noise source for producing a comfort noise

signal, and a mixer for combining the comfort noise signal with the audio signal detected by the microphone, which has been conditioned to reduce the amount of the detected types of noise.

13. A two way communication device in accordance with claim 11 the noise suppression circuit further comprises an echo cancellation circuit for receiving the audio signal received from the remote radio source to be reproduced by the speaker and removing any speaker reproduced signal detected by the microphone.

14. A method for suppressing noise in an audio signal, the method comprising:

detecting with a plurality of different types of noise activity detectors including a babble noise activity detector and a stationary noise activity detector the presence of a plurality of different types of noise in the audio signal, each different type of noise activity detector being adapted to detect a different type of noise;

suppressing the detected type of noise in the audio signal using one of a plurality of different types of noise reduction circuits including a noise attenuation circuit and a noise subtraction circuit, where each noise reduction circuit is adapted for removing a different type of detected noise, where each noise reduction circuit respectively corresponds to one of the plurality of noise activity detectors with the noise attenuation circuit corresponding to the stationary noise detector and the noise subtraction circuit corresponding to the babble noise activity detector, when the respective detector detects the presence of the corresponding type of noise by selectively activating the respective noise reduction circuit, and wherein the noise attenuation circuit and the noise subtraction circuit are both activated when both the stationary noise activity detector and the babble noise activity detector detect the presence of the corresponding noise types for the stationary noise activity detector and the babble noise activity detector in the audio signal.