Audio masking and time-frequency expansions
B. Mulgrew · 2006
An alternative mechanism for audio masking is postulated. This mechanism is derived as a solution to the classic prob-lem of representing a signal as a linear combination of ba-sis functions which are only approximately orthogonal and hence are prone to leakage. This mechanism involves aug-menting each basis function or filter with an auxiliary filter. In this combined detection/estimation process the instanta-neous amplitude output of the auxiliary filter sets the mask-ing threshold for the basis filter. No interconnection between basis functions is required to compute this masking thresh-old. For a gammatone filter bank the auxiliary filter is formed from the cascade of the gammatone itself and a single zero notch filter. The single zero (in the z-plane) has the same fre-quency as the centre frequency as the gammatone filter and is at a radius dependent on its bandwidth. 1.