DETECTION AND RECOGNITION OF REPEATED TONES AND TONAL PATTERNS

This study examined the effect of multiple presentations on signal det ection and on signal recognition (identifying one signal from a set of four possible signals) for three different sets of signals. One set w as four sinusoids (100-ms duration, frequencies of 707, 1000, 1414, an d 2000 Hz). Two sets contained tonal patterns each made of a sequence of seven, 100-ms, sinusoidal components. In the first set, the four pa tterns consisted of the same seven sinusoids in different orders. In t he second set, the four patterns had the same order of relative freque ncies, but had frequencies from different 1/4 oct bands centered at 70 7, 1000, 1414, and 2000 Hz. All stimuli were adjusted to be equally de tectable in the presence of a continuous white noise (eta(0)=20 dB SPL ). Each trial contained 1, 2, 4, 8, or 16 presentations of a given sig nal plus noise (probability of a signal was 0.5) or noise alone. Detec tability of the sinusoids generally increased as the square root of th e number of presentations; detectability for the tonal patterns increa sed at a slower rate. Recognition was generally poorer than predicted by the recognition theorem [S. J. Starr, C. E. Metz, L. B. Lusted, and D. J. Goodenough, Radiology 116, 533-538 (1975)] and increased with m ultiple presentations only as much as expected from the increase in si gnal detectability.