Critical Bands and the Discrimination of Intensity Relations in Two-Tone Complexes

Abstract

The intensity relations within a two-tone complex were varied by setting one tone 0.5 to 4 dB below 70 dB SPL and the other the same number of decibels above. 25 subjects, listening monaurally through earphones, tried to distinguish these complexes from complexes with both tones at 70 dB. The main variable was the frequency separation ΔF between the two tones. It was usually more difficult to detect an intensity difference within the complex when the two tones were close or far apart in frequency than when they were at some intermediate distance, roughly equal to the critical bandwidth. The effect of ΔF was clearest when the lower-frequency component was more intense than the higher-frequency component. Measures were also made with the intensity of the two components changed in the same rather than opposite directions. Here detectibility was independent of ΔF. These findings held up best at center frequencies of 1000 and 2000 cps, less well at center frequencies of 500 and 4000 cps. [Research supported by the Public Health Service, U. S. Department of Health, Education, and Welfare.]