Patent ID: 6173258
Filing Date: 2001-01-09
Classification: G10L

Abstract:
A system for reducing noise distortions in speech data, comprising:a feature extractor configured to perform a manipulation process on said speech data, wherein said feature extractor is comprised of:a noise suppressor that performs a spectral subtraction procedure on said speech data, which is expressed by a formula: ##EQU8##where Y.sub.D (Y) is a signal-to-noise ratio or a distorted estimation of clean speech, Y is a power or magnitude spectrum of noisy speech, N is an estimate of a power or magnitude noise spectrum, .alpha. is an over-estimation factor, and .beta. is a spectral flooring parameter; anda first time cosine transform that converts said static features into delta features, and a second time cosine transform that converts said static features into delta-delta features, wherein said first time cosine transform and said second time cosine transform each perform a centered-mode time cosine transform procedure that may be expressed by a following formula: ##EQU9##where C.sub.t (p) is a p.sup.th cepstral coefficient at a time frame t, M is half of a window size used to estimate differential coefficients, and o is a derivatives order with a value of one when corresponding to said delta features and a value of two when corresponding to said delta-delta features.