Relations between neural-count and intensity-jnd functions for single auditory-nerve fibers
William S. Hellman, Rhona P. Hellman · The Journal of the Acoustical Society of America · 1989
The equation d'σ(x) = ΔN(x), where x = I/I0, is applied to physiological measurements reported by Delgutte [The Psychophysics of Speech Perception (1987)] for single auditory-nerve fibers. Intensity-jnd functions are derived for individual fibers with the neural-count function as input. The experimentally obtained neural counts are represented by a hyperbolic tangent function, and the measured dependence of the count variance on the count is approximated by a combination of linear functions. Here, ΔN(x) can be obtained without approximation for arbitrary values of Δx for a hyperbolic tangent function; it can also be represented by a Taylor series in Δx. The exact equation for ΔN(x) gives a U-shaped jnd function in agreement with the numerical procedure used by Delgutte. By comparison, the Taylor series for ΔN(x) converges to the exact solution in fifth order. [Partially supported by the Rehabilitation Research and Development Service of the VA.]