Approximating the critical bands using warped filter banks based on multiplierless allpass chains

This paper shows that extending cosine-modulated warped filter banks with subband merging makes it possible to approximate the critical bands using frequency warpings determined by allpass functions with coefficients which are negative integer powers of two. Because binary shifts and additions are sufficient to perform such allpass filtering, the systems under consideration can be implemented much more efficiently than warped filter banks with unconstrained allpass functions. Especially, fixed-point arithmetics can be used or even low-power multiplierless circuits can be developed.