Detection and recognition of repeated tones and tonal patterns

This study examined the effect of multiple presentations on signal detection and on signal recognition (identifying one signal from a set of four possible signals) for three different sets of signals. One set was four sinusoids (100-ms duration, frequencies of 707, 1000, 1414, and 2000 Hz). Two sets contained tonal patterns each made of a sequence of seven, 100-ms, sinusoidal components. In the first set, the four patterns consisted of the same seven sinusoids in different orders. In the second set, the four patterns had the same order of relative frequencies, but had frequencies from different 1/4 oct bands centered at 707, 1000, 1414, and 2000 Hz. All stimuli were adjusted to be equally detectable 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 signal plus noise (probability of a signal was 0.5) or noise alone. Detectability of the sinusoids generally increased as the square root of the number of presentations; detectability for the tonal patterns increased 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 multiple presentations only as much as expected from the increase in signal detectability.