Noise reducing method, noise reducing apparatus and telephone se

Details Noise reducing method, noise reducing apparatus and telephone se Noise reducing method, noise reducing apparatus and telephone se

1996-08-14

1997-11-11

MacDonald, Allen R.

Electrical audio signal processing systems and devices

Hearing aids, electrical

Specified casing or housing

395 236, 395 237, 395 242, 381 57, 381 684, 381 731, 381 94, G10L 900

Patent

active

056872852

ABSTRACT:
A noise reducing method and device for reducing the noise contained in an input speech signal collects the speech signal with a microphone 11 and converts the speech signal into a digital input signal x(n) with an A/D converter 12. A frame power calculating circuit 13 calculates a mean frame power rms for each frame of the digital input signal x(n). A suppression ratio calculating circuit 14 calculates different values of the noise suppression ratio depending on the magnitude of the mean frame power rms relative to pre-set threshold values. A level discrimination circuit 18 forms a changeover control signal depending on the noise level and transmits the changeover control signal to the suppression ratio calculating circuit 14 for switching control of the threshold value. The suppression ratio value from the suppression value calculating circuit 14 is transmitted via a smoothing circuit 15 to a noise-reducing circuit 16 and multiplied with the input signal x(n) for reducing the noise component of the speech signal. The effect of the noise-reducing operation is changed in response to the noise level and the intensity of the noise-reducing operation is moderated in portions having a low noise level to prevent deterioration in the sound quality.

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