1 Towards a wearable frication transposer for severely hearing impaired persons - based on digital processing techniques D. Bauer, A. Plinge, M. Finke Institut für Arbeitsphysiologie, 44139 Dortmund, Ardeystr. 67 Tel. +49-0231-1084-265 Email: Bauer@arb-phys.uni-dortmund.de Keywords: sensory hearing loss, frication transposer, digital processing Abstract. For recovery of speech intelligibility, severely hearing impaired people with a near-total loss of sensitivity at frequencies above 2KHz urgently need a replacement of perceptional missing frication speech features. Depending on the damage, /s/, frication of /z/, /ç/, and sometimes /t/ and /k/ are important candidates for replacement. A lot of effort can be seen in the literature to compensate the losses by transposing the missing part of the spectrum; however no real breakthrough by wearable equipment is visible. The possible reasons are identified and a concept has been tested which uses predefined, well-accepted replacement sounds. The first results have been collected by use of an analogue design; however, analogue technique has its intrinsic limitations and cannot be the basis of wearable equipment. Therefore, to open up the chance to get a reliable, stable, and wearable transposer, a change to digital processing has been done: A set of C routines is under test which does all the filtering, decision making and generation of replacement stimuli required, cp. Plinge et al.[1] (this volume). 1. Introduction: From User Needs to Technology Our special target group are users who would not be able to draw sufficient benefit from the use of conventional hearing aids only. They are at the borderline between Cochlea-Implant patients and those patients suffering from only moderate sensory loss. M a i n area o f con s on a nt s f u n d a m e n t a l 0 40 80 100 130 0,25 0,5 1 2 4 8 kHz F1 F2 damage limit threshold residual hearing area level of discomfort c o n s o n a n t s H i g h ~45dB ~80dB y-e-i k-t c-s,z transposed Figure1 Typical case of severe sensory hearing deficit