Pure-tone anomalies. I. Pitch-intensity effects and diplacusis in normal ears.

Pitch-intensity functions were obtained in both ears of five normal-hearing subjects, together with measurements of binaural diplacusis as a function of intensity. The results show that pitch-intensity functions are often significantly different in the two ears of a given subject at a given frequency. Furthermore, for each subject and frequency condition tested, an intensity existed for which no significant diplacusis was found. For these conditions, therefore, binaural diplacusis as a function of intensity could be accounted for by the interaural differences in pitch-intensity functions. Forward-masking patterns (FMP's) as a function of intensity were also obtained in both ears of several subjects. The FMP's were compared with pitch-intensity functions, obtained for the same conditions, for evidence of a covariation in the direction of shifts in masking patterns as a function of intensity with the direction of pitch shifts as a function of intensity. No convincing evidence of such a covariation was found. The implications of the results of these experiments are discussed relative to the question of temporal versus tonotopic coding of pure-tone pitch.