L'intelligibilit'ea Des Messages Vocaux Contemporains En Conditions Normales Et Pathologiques

Abstract

The interference of a disturbing message with another message sent at the same time to a person under examination has been studied.

These researches have been carried out on subjects both with normal and impaired hearing by the mono-auriculair, the binauculair way, and in a free field. In patients with a normal hearing the understanding of the examined text appears to be directly proportional to both its output intensity and the intensity of the disturbing message, and is inversely proportional to the difference of intensity existing between the examined and the disturbing message.

This fact is more evident in the experiments made in a free field and by the binauricular way, as they are integrated by the auditory space-localisation. On the contrary, in patients with impaired hearing the intelligibility of the examining text decreases considerably in bilateral and especially in mono-auricular deafness. It can be assumed that the action of the disturbing message may cause a psychological disorder at the level of the central nervous system, even if it is able to reject undesired messages. This balance between both messages, while allowing a good understanding in normal subjects, is abolished in deaf patients because, just owing to their deafness, they receive a smaller quantity of informative impulses at the central level.

With stronger reason, these conditions subsist in carriers of acoustic prostheses, owing to the presence of simultaneous messages, surrounding noises, etc. concentrated in a single ear.