ISBN 9783843927703

978-3-8439-2770-3, Reihe Ingenieurwissenschaften

Daniel Marquardt
Development and evaluation of psychoacoustically motivated binaural noise reduction and cue preservation techniques

200 Seiten, Dissertation Carl von Ossietzky Universität Oldenburg (2015), Hardcover, B5

Zusammenfassung / Abstract

Due to their decreased ability to understand speech hearing impaired may have difficulties to interact in social groups, especially when several people are talking simultaneously. Fortunately, in the last decades hearing aids have evolved from simple sound amplifiers to modern digital devices with complex functionalities including noise reduction algorithms, which are crucial to improve speech understanding in background noise for hearing-impaired persons.

The main objective of this thesis is to develop and evaluate algorithms for noise reduction in binaural hearing aids, which, in addition to preserving the binaural cues of the speech component, also preserve the binaural cues of the noise component. Generally, the proposed algorithms are based on the binaural multi-channel Wiener filter (MWF), since this technique advantageously combines spatial filtering with spectral filtering and preserves the binaural cues of the speech source.

For acoustic scenarios with a single speech source in a diffuse noise field, we propose two extensions of the binaural MWF, namely the MWF-IC and the MWF-N, aiming to also preserve the Interaural Coherence (IC) of the diffuse noise field. Since for both algorithms a trade-off between IC preservation and noise reduction performance exists, depending on trade-off parameters, we propose to select these trade-off parameters based on the IC discrimination ability of the human auditory system. We evaluate the proposed algorithms using objective measures and subjective listening tests, showing that the proposed algorithms always improve the spatial impression of the output signal and can in some cases even increase speech intelligibility compared to the binaural MWF.

For acoustic scenarios with a single speech and an additional interfering source in a diffuse noise field, we propose two extensions of the binaural MWF which either aim to preserve the relative transfer function of the interfering source (MWF-RTF) or to completely reject the interfering source (MWF-IR). We provide a rigorous theoretical analysis and comparison of the performance of the binaural MWF, MWF-RTF and MWF-IR algorithms, showing that the MWF-RTF achieves a very similar overall noise reduction performance as the binaural MWF, while preserving the binaural cues of both the speech source and the interfering source, whereas the overall noise reduction performance of the MWF-IR is significantly degraded compared to the binaural MWF.