Adaptation auditive et localisation

Abstract
This paper presents the main results of an experiment on the possible role of adaptation in auditory localization. Measurements are performed in an anechoic room on the apparent azimuth of a brief 4-kHz tone, coming from the side (15°) of the listener, in the presence of a tone at the same frequency coming from the front. This frontal source is turned on first, for a certain amount of time, in order to induce some sort of auditory adaptation ; next, a 50-ms tone is presented from the lateral source. It is found that, as the duration of the pre-exposure is increased, the apparent azimuth of the second sound varies under some conditions ; in most cases, it is shifted towards the side of the subject, away from the actual position of the source. The same type of effect is demonstrated under earphones. In this case, the adapting signal is a diotic tone, and the adapted signal is a 50-ms dichotic tone with an interaural time difference of 70 µs. The summation of these tones leads to an interaural level difference, and therefore to a lateralized auditory image. The apparent location of this image also varies with adaptation, as in the first experiment.