Suppression of reverberation in hearing aids

In this report we will talk about Suppression of reverberation in hearing aids. Reverberation is actually a sound degradation which lead to reduced speech intelligibility. For a hearing impaired person putting on a hearing aid, this could cause communication problems and therefore, the motivation for a dereverberation algorithm for hearing aids is obvious. Reverberation is created by propagation delays from reflective boundaries surrounding the source and the receiver of a sound, and is regarded as temporal smearing by the listener.

Three common approaches for dereverberation are considered and examined theoretically. Although inverse filtering and speech coding methods are ignored due to time delay requirements not met and time constraints of the project, beamforming techniques are researched further. One additive beamformer is implemented plus an adaptive subtractive beamformer, both operating in frequency bands.

To assess the performance, a great deal of effort is put into developing a test setup for the reverberation problem. Simulated impulse responses are produced with the image method and real impulse responses are recorded with diverse methods, the effect on speech intelligibility by reverberation and noise is investigated and a test program for speech intelligibility by listening tests is implemented.

The outcomes imply that articulation-index signal-to-noise ratio quantify dereverberation best among the common objective measures of speech intelligibility researched. The listening tests reveal that the subtractive beamformer method is a superb algorithm for increased speech intelligibility by dereverberation whilst the additive algorithm is not. The resulting increase in speech intelligibility is quantified to +2.0 dB for the subtractive beamformer algorithm however the additive beamformer algorithm decreases the speech intelligibility with -1.4 dB………

Suppression of reverberation in hearing aids downloads

Source: Lulea University of Technology

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