1. A method for masking quantization noise by spectrally weighting transform coefficients of an input signal having a given bandwidth and produced by a transform processor, comprising: calculating a masking spectral threshold in a quasi-logarithmic scale that approximates critical bands of a hearing model by applying triangular decays to spectral peaks; computing plural spread masking thresholds in each critical band as a maximum of contributions from the triangular decays; and adjusting the spread masking thresholds to produce an absolute threshold.