Dirk Mauler

Improved reproduction of stops in noise reduction systems with adaptive windows and nonstationarity detection

A new block-based noise reduction system is proposed which focuses on the preservation of transient sounds like stops or speech onsets. The power level of consonants has been shown to be important for speech intelligibility. In single-channel noise reduction systems, however, these sounds are frequently severely attenuated. The main reasons for this are an insufficient temporal resolution of transient sounds and a delayed tracking of important control parameters. The key idea of the proposed system is the detection of non-stationary input data. Depending on that decision, a pair of spectral analysis-synthesis windows is selected which either provides high temporal or high spectral resolution. Furthermore, the decision-directed approach for the estimation of the a priori SNR is modified so that speech onsets are tracked more quickly without sacrificing performance in stationary signal regions. The proposed solution shows significant improvements in the preservation of stops with an overall system delay (input-output, excluding group delay of noise reduction filter) of only 10 milliseconds.

Optimization of switchable windows for low-delay spectral analysis-synthesis

We present a novel iterative method for the optimization of switchable pairs of window functions. These windows may be used for block-based spectral analysis-synthesis (AS) in low-delay speech enhancement systems, where the energy compaction of speech sounds is improved by switching the spectral AS windows. Optimization objectives of the approach take the frequency response, quasi perfect reconstruction (PR) of each window pair and quasi-PR during window switching into account. An example of window pairs obtained with the proposed method clearly outperforms a reference design. The improved aliasing and imaging suppression is particularly important for hearing aids where high spectral gains may lead to audible reconstruction artifacts.

Signal processing in Hearing Aids: Results of the HEARCOM project

Digital hearing aids of today allow the application of advanced signal processing strategies. In recent years a number of promising signal processing approaches have been designed and developed. However, most of these different evolutions have been evaluated only in a limited way. Within the framework of the HEARCOM EU‐research project a number of signal enhancement techniques have been further developed and evaluated based on a representative set of real‐life recordings and physical performance measures. Different auditory profiles, representing common categories of hearing aid users, have been taken into account. A selection of 5 of these signal enhancement techniques (single‐channel noise suppression, blind source separation, dereverberation, multi‐microphone adaptive processing, feedback reduction) has been implemented on a single common hard‐ and software test platform, the Master Hearing Aid (MHA). These signal processing strategies have been evaluated perceptually based on speech reception threshol...