Patent ID: 6604071
Filing Date: 2003-08-05
Classification: G10L

Abstract:
A method for enhancing a speech signal for use in speech coding, the speech signal representing background noise and periods of articulated speech, the speech signal being divided into a plurality of data frames, the method comprising the steps of:applying a transform to the speech signal of a data frame to generate a plurality of sub-band speech signals; making a determination whether the speech signal corresponding to the data frame represents articulated speech; determining the individual gain values and wherein, for a given data frame, the lower limit for gain values is a function of a lower limit for an a priori signal to noise ratio, wherein the lower limit for the a priori signal to noise ratio for the data frame is determined with use of a first order recursive filter which combines a lower limit for an a priori signal to noise ratio determined for a previous data frame and a preliminary lower limit for the a priori signal to noise ratio of the data frame; applying individual gain values to individual sub-band speech signals, wherein a lower limit for gain values applied for a data frame determined to represent articulated speech is lower than a lower limit for gain values applied for a data frame determined to represent background noise only; and applying an inverse transform to the plurality of sub-band speech signals.