Communication system with adaptive noise suppression

Details Communication system with adaptive noise suppression Communication system with adaptive noise suppression

2007-04-24

2007-04-24

Pendleton, Brian T. (Department: 2615)

Electrical audio signal processing systems and devices

Noise or distortion suppression

Spectral adjustment

C704S226000, C704S233000

Reexamination Certificate

active

10390259

ABSTRACT:
A signal-to-noise ratio dependent adaptive spectral subtraction process eliminates noise from noise-corrupted speech signals. The process first pre-emphasizes the frequency components of the input sound signal which contain the consonant information in human speech. Next, a signal-to-noise ratio is determined and a spectral subtraction proportion adjusted appropriately. After spectral subtraction, low amplitude signals can be squelched. A single microphone is used to obtain both the noise-corrupted speech and the average noise estimate. This is done by determining if the frame of data being sampled is a voiced or unvoiced frame. During unvoiced frames an estimate of the noise is obtained. A running average of the noise is used to approximate the expected value of the noise. Spectral subtraction may be performed on a composite noise-corrupted signal, or upon individual sub-bands of the noise-corrupted signal. Pre-averaging of the input signal's magnitude spectrum over multiple time frames may be performed to reduce musical noise.

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