DETECTION OF FREQUENCY CHANGES IN TRANSPOSED SEQUENCES OF TONES

The ability to detect frequency changes in transposed sequences of ton es was examined in a series of seven experiments. Listeners were asked to judge which of two transposed (i.e., frequency-shifted) comparison patterns preserved the sequence of relative frequencies presented in a preceding standard pattern. The task was performed with five-tone an d two-tone patterns under conditions of high and minimal pattern uncer tainty. Regardless of pattern length. or level of uncertainty, frequen cy discrimination thresholds for a change in the relative frequency df a single tone were considerably higher when patterns were transposed than when they were not. There was a tendency for performance to worse n with increasing degrees of transposition (primarily under high uncer tainty) but most of the detrimental effects of transposition occurred within the first two semitones of transposition. Minimal uncertainty t esting resulted in large improvements with five-tone patterns (as much as one order of magnitude), but there was no effect of level of uncer tainty on performance with two-tone patterns. Thresholds for changes i n two-tone patterns were similar to (although slightly higher than) th ose for five-tone patterns under minimal-uncertainty testing. This pat tern of results reveals that the effects of stimulus complexity (seque nce length) and pattern familiarity (level of uncertainty) on relative -frequency discrimination are quite similar to the effects of these va riables on absolute-frequency discrimination. (C) 1996 Acoustical Soci ety of America.