Digital Speech Signal Processing to Compensate Severe Sensory Hearing Deficits: The /s, z, C, t/ Transposer Module in Simulation - An Overview and Examples

Abstract

We start by considering the needs of users who until now cannot receive badly needed technical compensation for their auditory deficit - because of a lack of efforts to develop special assistive devices for the smaller populations within mainstream industrial development: These patients are characterised by the existence of severe sensory deficits; they are often unable to draw sufficient benefit from conventional hearing aids nor are they candidates for cochlear implants. If we consider the possibilities of residual reception of sensory information within this group -particularly when the auditory cortex has received good training, substantial chances of improvement of speech reception can be identified - if current technical shortcomings could be eliminated. Today, unacceptable limits to verbal speech communication exist in too many communication situations. Technical requirements, arising from user needs on the background of users’ residual physiological processing, are the starting point of our approach. The goal should be to effectively replace the lost auditory functions by external processing: Not only a compensation of losses in spectral sensitivity and spectral dynamical ranges is required to make feature information audible; we must also direct our attention more specifically to the compensation of losses of selectivity in phonetic cortical pattern recognition. The concept of various technical functions of a “speech processing system”, which may be added to hearing aids, are outlined: dedicated technical functionalities are grouped into a “front end”, a “baseband processor”, a “phonetic-element-replacement module”, and a “wireless-coupling to the hearing-aids” unit.