The use of a loudness model to derive initial fittings of multi-channel compression hearing aids.

Abstract

A model of loudness perception applicable to hearing-impaired people has been used to develop three methods for the initial fitting of hearing aids with multi-channel compression, based on the audiometric thresholds. Method one, CAMEQ, has the goals of amplifying speech so that, on average, the specific loudness is the same for all frequencies within the range 500–4000 Hz, over a wide range of overall sound levels, giving about the same overall loudness as “normal” for speech covering a wide range of sound levels. Method two, CAMREST, determines the gains needed give normal specific loudness patterns for speech over a wide range of sound levels. Method three, CAMEQ2-HF, is similar to CAMEQ but differs from it in the following ways: (1) gains are recommended for center frequencies up to 10 kHz (as compared to 6 kHz for CAMEQ), (2) CAMEQ2-HF is based on the assumption that the user may wish to hear sounds from many directions and uses a diffuse-field-to-eardrum transfer function (as opposed to a free-field-to-eardrum transfer function for CAMEQ); (3) CAMEQ2-HF is based on recent wideband measurements of the average spectrum of speech. All of the methods can be applied to any multi-channel compression hearing aid.