A class of warped filter bank frames tailored to non-linear frequency scales

TL;DR

This paper introduces a flexible method for constructing non-uniform filter banks using warping functions, unifying and extending classical Gabor and wavelet systems, and enabling adaptation to perceptual frequency scales.

Contribution

It proposes a novel framework for warped filter bank frames based on warping functions, allowing tailored non-uniform frequency analysis including perceptually motivated scales.

Findings

Constructs a broad class of warped filter bank frames.

Provides conditions for frame properties based on prototype decay and decimation.

Includes methods for creating tight, bandlimited filter bank frames.

Abstract

A method for constructing non-uniform filter banks is presented. Starting from a uniform system of translates, generated by a prototype filter, a non-uniform covering of the frequency axis is obtained by composition with a warping function. The warping function is a $\mathcal C^1$-diffeomorphism that determines the frequency progression and can be chosen freely, apart from minor technical restrictions. The resulting functions are interpreted as filter frequency responses. Combined with appropriately chosen decimation factors, a non-uniform analysis filter bank is obtained. Classical Gabor and wavelet filter banks are special cases of the proposed construction. Beyond the state-of-the-art, we construct a filter bank adapted to a frequency scale derived from human auditory perception and families of filter banks that can be interpreted as an interpolation between linear (Gabor) and logarithmic (wavelet) frequency scales. We derive straightforward conditions on the prototype filter decay and the decimation factors, such that the resulting warped filter bank forms a frame. In particular, a simple and constructive method for obtaining tight frames with bandlimited filters is derived by invoking previous results on generalized shift-invariant systems.