PURE TONE INTENSITY DISCRIMINATION AND DYNAMIC RANGE ADAPTATION
Résumé
Electrophysiological animal studies have shown that in response to a noise fluctuating in level, neurons adapt their dynamic range according to the level distribution. This Dynamic Range Adaptation (DRA) shifts the neurons' input-output growth function towards the most probable levels. The present study investigates the effect of context on intensity discrimination, in search of a perceptual correlate of DRA. Nine normal-hearing participants took part. Intensity difference limens (DLs) were measured for 2-kHz, 50-ms pure tones at 55-and 75-dB SPL, embedded in sequences of 50-ms narrowband non-simultaneous noise with a Gaussian level distribution centered around 55-or 75-dB SPL. The hypothesis was that DRA should yield lower DLs for matched tone and context levels than for unmatched levels. The results showed a significant interaction between tone level and context level but not consistent with DRA: DLs remained larger for the loud than for the soft context for both tone levels. Possible explanations include (i) the use of different stimuli compared to the animal studies, (ii) the presence of off-frequency listening which may lower DLs when the tone level is higher than the context level, and (iii) differences in absolute thresholds between context levels, which may affect DLs more than DRA.
Domaines
Acoustique [physics.class-ph]
Origine : Fichiers produits par l'(les) auteur(s)