Perceptual grouping in audition.

The present experiments evaluated the effect of relative frequency as a determinant of the figure-ground organization of sequences of auditory tones. Observers counted sequences of 20 ms tones that were presented at the same frequency or that alternated between two different frequencies. The alternating tones differed in frequency by one whole tone, seven tones, or nineteen tones. Counting accuracy increased with increases in the silent interval between the tones. When the alternating tones differed by seven or nineteen tones, counting was disrupted at rates of presentation of eight tones per second or slower. In contrast to this decrement in the counting of tones that alternated by over an octave, very little decrement was observed when the tones alternated by just one whole tone. The best subjects counted these alternating tones more accurately than the tones presented at the same frequency. The poorest subjects showed a small decrement even when the tones alternated by just one whole tone. The results were discussed in terms of determinants of figure-ground organization in auditory information processing.