Audio masking and time-frequency expansions

An alternative mechanism for audio masking is postulated. This mechanism is derived as a solution to the classic problem of representing a signal as a linear combination of basis functions which are only approximately orthogonal and hence are prone to leakage. This mechanism involves augmenting each basis function or filter with an auxiliary filter. In this combined detection/estimation process the instantaneous amplitude output of the auxiliary filter sets the masking threshold for the basis filter. No interconnection between basis functions is required to compute this masking threshold. 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 frequency as the centre frequency as the gammatone filter and is at a radius dependent on its bandwidth.