Responses of Auditory-nerve Fibers to Multiple-tone Complexes

To relate level-dependent properties of auditory-nerve-fiber responses to nasal consonant-vowels to the basic frequency selective and suppressive properties of the fibers, multitone complexes, with the amplitude of a single (probe) component incremented, were used as stimuli. Quantitative relations were obtained between the systematic increase of fiber synchrony to the probe tone and the decrease of synchrony to CF, as the amplitude of the probe tone was increased. When such relations are interpreted as a measure of fiber frequency selectivity based on a relative synchrony criterion, a breadth of frequency tuning is obtained, at a 70-dB SPL multitone sound-pressure level, which is generally broader than that of the fiber's threshold tuning curve. Quantitative comparisons with the same fiber's responses to the nasal speech sounds indicate that the fiber's speech responses share some common features with its probe-tone responses.