par Bosquet, Jean Paul Emile
Référence Biosciences Communications, 4, 3-4, page (160-174)
Publication Publié, 1978
Article révisé par les pairs
Résumé : In 1970, Korn showed that 'elementary messages of discrete frequency' (EMDIF) f(t) divided by t2 exp (-αt) cos (ωt+φ) defined, for any discrete angular frequency ω, by an experimentally defined critical value of α , is perceived as a pure tone without subjective duration. Starting from that, the ear is assumed to be synthetically equivalent to a filterbank whose impulse responses are identical to the EMDIF. The response of the filterbank corresponding to a stimulus is a set of functions of time, localized by a frequency parameter, constituting thus the variable peripheral spectrum. It is known that the system of hair cells and nerve fibers (NS), which 'reads' the peripheral spectrum, act as detectors, have finite impulse responses and perform a 'lateral inhibition' function. The model shows that the lateral inhibition occurs when the spectrum presents a critical shape corresponding to the response of an EMDIF, at a critical instant θ(c) of maximum sensibility. Assuming the shape divided by t2 exp (-βt) for the impulse of the NS, values of β are deduced from published PST histograms. The model enables us to determine numerically: (1) the phase velocity of the 'travelling wave' and the variation of the phase (3π) along the filterbank; (2) the perception of the temporal envelope of a long stimulus; (3) a universal masking spectrum, with 'notches' corresponding to the 'freezing' of the beats in the immediate vicinity of the instant θ(c); (4) a universal 'subjective' spectrum; (5) the 'thickness of the present' corresponding to a 'temporal masking' effect; (6) a rational explanation of the phenomenon of the beats and of their roughness; (7) the just noticeable time difference between successive 'clicks'.