Sophie Scott
Dept. of Psychol., Univ. College, Gower St., London WC 1E 6BT, England
Peter Howell
University College, London WC 1 E 6BT, England
Acoustic signals have a perceptual moment of occurrence, called the ``perceptual center'' or ``P-center'' [Morton et al., Psychol. Rev. 83, 405--408 (1976)]. No simple acoustic correlates of P-center location, such as vowel onset, physical onset, and peak amplitude, have been found. What has not been accounted for, however, is distortion of the acoustic signal by the experimental equipment. This can lead to discrepancies between measured attributes of the signal, and the signal which reaches the subject's ear. The degree of amplitude and phase distortion has been calibrated, and a comparison made of the standard TDH-39 headphones, against ER-2 insert earphones, for amount of signal distortion. The effect of this distortion upon the acoustic attributes that have been previously dismissed as determiners of P-center location, is discussed. A model for P-center location based on the distribution of energy over time in the signal is outlined.