The application relates to a filter bank for an audio processing device, e.g. a hearing aid. The filter bank comprises an analysis filter bank comprising a plurality of M first filters hm(n), where m=0, 1, . . . , M−1 is a frequency band index, n being a time index, the first filters hm(n) having a first filter length of Lhm; a synthesis filter bank comprising a plurality of M second filters gm(n), m=0, 1, . . . , M−1, the second filters gm(n) having second filter lengths of Lgm; the plurality of first and second filters being arranged in pairs, each pair forming a frequency channel. the first filters hm(n) exhibiting a first filter delay τh, the second filters gm(n) exhibiting a second filter delay τg, each of the first filter lengths Lhm and the second filter lengths Lgm is uneven, and wherein the first filters are subject to the constraint that the sum of the first filters hm(n) of the analysis filter bank is a delta function δ(n−τh).