Preserving binaural hearing of hearing impaired subjects with binaural noise reduction systems for hearing aids
Tim Van den Bogaert, Simon Doclo, Jan M Wouters, Marc Moonen · Lirias · 2009
Hearing aid users experience great difficulty in understanding speech in noisy environments. This has led to the introduction of noise reduction algorithms in hearing aids. The development of these algorithms is typically done monaurally. However, the human auditory system is a binaural system, which compares and combines the signals received by both ears to perceive a sound source as a single entity in space. Providing two monaural, independently operating, noise reduction systems, i.e. a bilateral configuration, to the hearing aid user may disrupt binaural information, needed to localize sound sources correctly and to improve speech perception in noise. We first examine the influence of commercially available, bilateral, noise reduction algorithms on binaural hearing. Extensive objective and perceptual evaluations with normal hearing and hearing impaired subjects show that the bilateral adaptive directional microphone (ADM) and the bilateral fixed directional microphone, two of the most commonly used noise reduction algorithms in hearing aids, can significantly distort the binaural properties of the sound signals. As a second step, binaural noise reduction schemes based on a multichannel Wiener filter (MWF) approach are developed and evaluated. It is observed that a binaural hearing aid design significantly increases noise reduction performance owing to the larger number of microphones used. Moreover, the binaural MWF and the binaural MWF with partial noise estimation (MWF-N) provide a better combination of noise reduction performance and preservation of binaural cues (localization performance in the horizontal hemisphere) compared to the bilateral ADM algorithm.