Two-tone masking in normal hearing listeners

Abstract

Psychophysical measurements of two-tone masking [E. Zwicker, Acustica 4, 415–420 (1954)] were made at 0.25, 0.5, 1, 2, and 4 kHz utilizing a masker level of 62 dB SPL/tone. Fifty-eight ’’untrained’’ subjects were tested using a single run of a 4IFC adaptive procedure for each condition. Individual data were highly variable. Average data were systematic; they were analyzed using a two-line-regression procedure and the obtained critical-bandwidth estimates approximated normative values. Analysis of the literature revealed that a substantial increase of estimated critical bandwidth versus masker level occurs in two-tone masking. A portion of this increase appears artificial and stems from the relative ineffectiveness of the higher frequency masker tone at high masker levels. An alternative masker-frequency spacing is suggested to reduce level effects. Implications for an underlying critical-band mechanism are discussed.