Appell, Jens-E. and Hohmann, V. and Kollmeier, Birger
Dynamic compression hearing aids are used for compensating sensorineural, hearing loss, i. e. the so called ''Recruitment-Phenomenon'', (pathological increase of loudness). Their principles and basic problems, will be discussed first. In order to attain an improved design and, fitting of current 3-channel compression hearing aids, a, master-hearing-aid algorithm was implemented on a digital signal, processor and speech intelligibility measurements and quality tests were, performed with sensorineurally hearing impaired subjects. Three, processing schemes were used: a linear hearing aid (reference, algorithm), a syllabic-compression algorithm (time constants between 3, and 50 msec, low compression ratio, compression threshold at about 20 dB, HL) and an Automatic Volume Control (AVC)-algorithm (time constants 200, msec, high compression ratio, compression threshold at about 20 dB HL)., Only small differences were observed with the digitally implemented, algorithms. These differences could only be detected because a uniform, hardware and a clear concept for the fitting procedure was employed., Advantages of the dynamic compression algorithms were mainly observed at, low and high input levels. In general the best results were found for, the AVC-Algorithm.