SS07: PSYCHOACOUSTICS, SPEECH PERCEPTION AND AUDITORY SIGNAL PROCESSING

USE OF A LOUDNESS MODEL TO DERIVE A METHOD FOR FITTING HEARING AIDS WITH EXTENDED HIGH-FREQUENCY BANDWIDTH

Moore B

Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge, CB2 3EB, UK

A loudness model applicable to impaired hearing (Moore and Glasberg, 1997) was used previously to develop two methods for fitting multi-channel compression hearing aids, CAMEQ, and CAMREST.  These two methods give recommended gains for frequencies up to 6000 Hz, which is close to the highest frequency at which most hearing aids provide useful gain.  However, several manufacturers now market hearing aids that are claimed to provide useful gain at frequencies above 6000 Hz.  To derive recommended gains at high frequencies, we measured the typical spectro-temporal characteristics of speech at high frequencies (Moore et al., 2008), and used a revised loudness model (Moore and Glasberg, 2004) to derive gains as a function of frequency and level that would: (1) lead to at least 50% of the dynamic range of speech being above absolute threshold for frequencies from 5000 to 10000 Hz, for speech with an overall level of 65 dB SPL; (2) avoid a specific loudness that was greater than normal at high frequencies; (3) lead to a similar overall loudness to normal.  The modelling outcomes show that, for the great majority of hearing-impaired people, it is not practical to aim to restore the audibility of frequency components of speech above about 10000 Hz.

Moore, B. C. J., Glasberg, B. R., 1997. A model of loudness perception applied to cochlear hearing loss. Auditory Neurosci. 3, 289-311.

Moore, B. C. J., Glasberg, B. R., 2004. A revised model of loudness perception applied to cochlear hearing loss. Hear. Res. 188, 70-88.

Moore, B. C. J., Stone, M. A., Füllgrabe, C., Glasberg, B. R., Puria, S., 2008. Spectro-temporal characteristics of speech at high frequencies, and the potential for restoration of audibility to people with mild-to-moderate hearing loss. Ear Hear. 29, 907-922.