ABSTRACT

Dynamic changes in acoustic intensity can produce perceptual changes in pitch as large as half an octave. Here we investigate the functional roots behind these large distortions. We propose a natural acoustic regularity in which sound sources that change in fundamental frequency (f₀) typically congruently change in intensity, and vice versa. It is therefore adaptive for the auditory system to capitalize on this statistical regularity by integrally perceiving changes in pitch and loudness. This regularity could then provide a redundant cue that facilitates parsing and tracking of individual sources during auditory scene analysis. In three initial experiments testing music and speech, we find support for the proposed statistical correlation between changes in f₀ and intensity. In a fourth experiment, we utilize an adaptive staircase procedure to measure detection thresholds for tone-glides that changed in f₀, intensity, or both. The lowest detection threshold levels occurred when f₀ and intensity changed in the same direction. Our findings confirm an acoustical correlation between changes in f₀ and intensity in domains of music and speech, and support that listeners can parse and hear sounds better when they are consistent with this natural regularity.