ASA 127th Meeting M.I.T. 1994 June 6-10

3aPP5. Lateralization of a frequency-modulated 500-Hz tone.

R. W. Hukin

C. J. Darwin

Lab. of Exptl. Psychol., Univ. of Sussex, Brighton BN1 9QG, UK

Previous experiments [C. Trahiotis and R. M. Stern, J. Acoust. Soc. Am. 86, 1285--1293 (1989)] have shown changes in the lateralization of a bandlimited noise centered at 500 Hz with an ITD of 1.5 ms as its bandwidth is increased. The phenomenon is thought to be due to across-frequency integration of ITD information. The present experiment extends this phenomenon to an FM 500-Hz tone. With no FM the 500-Hz tone is heard on the lagging ear, but tones with appropriate rates and depths of FM are heard on the leading ear. Subjects indicated which of two FM tones (ITD=(plus or minus)1.5 ms) was heard more on the left. At 40 Hz FM, subjective lateralization changed at an FM depth of about 30%. At slower rates of FM, greater FM depth was needed to change subjective lateralization, so that at 5 Hz, about 45% modulation was needed. These results may be due to listeners integrating ITD information across both frequency and time. [Work supported by MRC.]