[Hearing aids rehabilitation: state of the art]

The three-dimensional characteristic of heari ng as a neurosensory loss can be associated with distortions in the axes of intensity, frequency and also temporal. This type of distortions can be isolated or combined, with many functional characteristics which complicate the fixing of the hearing aid and makes its result extremely variable. The ENT specialist in charge of the prescription of the hearing aid must know the various types of available devices, its indications and limitations. The different current hearing aids by acoustic stimulation are described, behind the ear, intra-auricular, intra-canal, micro-behind the ear with receiver in the canal (RIC). Some clinical and audiometric elements make it possible to envisage the difficulty of such equipment as the air bone gap, the dynamic, the frequential shift, the hearing discrimination. Concerning the hearing aid itself, the amplifier represents the fundamental part allowing the compensation of the quatitative loss; it presents however many possibilities of adaptation (multifrequential compression, the adaptive directionnality coming from the directional microphones, the suppression of the acoustic feedback, the increase of the bandwidth and software of statistical analysis of environmental acoustics as well as procedures of decision). Finally software of treatment of the signal like the software of suppression of acoustic feedback, identification of the speech and noise, of adaptive directionality, of measurement of the hearing thresholds (which is possible on certain prosthesis for each channel) refine the adjustment of the hearing aid.

The knowledge of these technological possibilities currently available, like their indications and limitations, allows the ENT specialist to get an active role in the process of acceptation of the hearing aid.