The higher audiometric frequencies arguably are the most important for some tasks requiring fine temporal discriminations. Both modulation and gap detection thresholds improve with increasing center frequency of noise bands. For modulation detection, however, not all investigators are convinced that improved performance is necessarily dependent on sensitivity at the higher center frequencies. They point out that the high-frequency advantage for modulation detection may be a consequence of concomitant increases in stimulus bandwidth as a function of increasing center frequency of the noise band. To determine whether signal frequency or signal bandwidth is more important for modulation and gap detection, modulation and gap detection thresholds were measured for low-pass (LP) filtered noise (fc = 4000 Hz, bandwidth = 4000 Hz), high-pass (HP) filtered noise (fc = 4000 Hz, bandwidth = 2500 Hz), and broadband (BB) noise (bandwidth = 6500 Hz). Modulation and gap detection thresholds for the BB and HP signals were similar, and were better than thresholds for the LP signal. The ability to hear the higher frequencies of the noise signal apparently is more important for these tasks than is perception of signal bandwidth. [Research supported by Division of Sponsored Research, University of Florida, and American Cancer Society.]

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