A device for processing a digital signal includes a Farrow structure (14) that applies to the digital signal a time-varying sample rate conversion from the fixed sample rate to a time varying sampling. The digital signal sampled at the time varying sampling is a resulting signal. The Farrow structure (14) is controlled from a control variable. A spectral analysis means (15) performs a spectral analysis of the resulting signal to determine the frequency values of the resulting signal. A determining means (16) determines a sparseness parameter of the frequency values of the resulting signal. A controlling means (17) modifies the control variable according to the value of the sparseness parameter.

Disclosed herein, among other things, are systems and methods for reducing the comb filtering for hearing devices. A method includes determining an effective time delay as a function of frequency between a direct path from a sound source to an eardrum of a wearer of a hearing device and an amplified path from the sound source through the hearing device to the eardrum of the wearer, and calculating a set of cancellation frequencies based at least in part on the determined effective time delay. The method also includes comparing an aided gain response and a real-ear occluded gain response of the hearing device, and determining one or more spectral interaction regions based at least in part on the comparison. A subset of cancellation frequencies is determined by comparing the spectral interaction regions with the set of cancellation frequencies, and a filter is constructed using the subset of cancellation frequencies and a determined attenuation configured to reduce comb filtering.