Compensation of Severe Sensory Hearing Deficits. Two Different Approaches to Replace Inaudible Speech Elements: Re-Sampling Versus Re-Synthesis

People who suffer from severe auditory high-tone losses would greatly benefit from replacement or selective enhancement of speech elements or speech features. We have tested two basically different technical methods of frequency transformation that are suitable for implementation on wearable DSP-add-on equipment in a C++ simulation: The first procedure consists of straight frequency transposition through re-sampling and digital interpolation. Here, intrinsic spectral and temporal relationships are more accurately preserved but can be perceptually matched only to a minor degree. The second one consists of controlled selective resynthesis of pre-selectable speech elements –such as /s, z, C, t/. This method features deliberate re-synthesis of the replacement sound, which then can explicitly be matched to the characteristics of the residual auditory system. Listening tests show that low-processing-cost realisations of both methods are useful, the range of applicability, however, is different.