John W. Hawks
Christine L. Sapp
School of Speech Pathol. and Audiol., Kent State Univ., Kent, OH 44242
Preliminary estimates to determine the relative amplitude relationship necessary for one spectral pattern to influence another in terms of the resulting periodicity pitch were made. The threshold of discrimination (DL) for a change in periodicity pitch was estimated for complex tones whereby either the even- or odd-order harmonic components were simultaneously decremented in amplitude. An adaptive up-down procedure employing a 2AFC task with two standards was utilized with minimally trained subjects. Stimuli were digitally constructed by summing sine waves spaced at 100-Hz intervals. Three stimulus parameters were evaluated: (1) total number of components (5 or 6); (2) position of varied components (even or odd order); and (3) frequency range (1400--1900 Hz or 2000--2500 Hz). Difference limens obtained ranged from -8.2 to -23.1 dB relative to the fixed component amplitude with an overall mean of -13 dB. The implications of these findings will be discussed.