Neal Viemeister’s contributions to understanding the dynamic range of the auditory system

Abstract

Most neurons in the auditory nerve show saturation of their firing rates in response to a tone with a moderate level presented at their characteristic frequency. However, humans can detect changes in intensity for levels up to 120 dB SPL. One explanation of this “dynamic range problem” is that intensity coding at high levels depends on the spread of cochlear excitation. To test this explanation, in 1974 Neal Viemeister measured the intensity discrimination of bursts of noise presented in a band-reject noise of fixed high intensity. He found that Weber’s law held even at high levels. He concluded that spread of excitation is not necessary for the auditory system to maintain its large dynamic range. In 1983 Neal Viemeister showed that, over a wide range of intensities, subjects could detect small differences in the intensity of a high-frequency band of noise (6-14 kHz, a frequency range where phase locking is essentially absent) presented with a complementary band-reject noise, showing that phase locking is not essential for intensity discrimination at high levels. In 1988 Neal Viemeister showed theoretically that a localized rate-based intensity code using a small number of neurons can account for intensity discrimination over a wide range of levels.