Spectral effects in the perception of pure and tempered intervals: Discrimination and beats

Abstract

Thresholds for discrimination between pure and tempered musical intervals consisting of simultaneous complex tones have been investigated previously (Vos. 1982). The aim of the present research was to answer three questions: (1) To what extent are these thresholds determined by the interference of just-noncoinciding harmonics? (2) Is the beat frequency of the first pair of these adjacent harmonics equal to the perceived beat frequency of the tempered intervals? (3) Are differences in discriminability at threshold representative of differences between the perceived strength of beats in supraliminal conditions? In the first three experiments, the answer to the first question was sought by investigating the effect of spectral content of the tones on the (Uscrimination thresholds (DTs) for the fifth (Experiment 1) and the major third (Experiments 2 and 3). The results showed that, for moderately tempered fifths, DTs are determined mainly by the interference of the first pair of adjacent harmonics. For major thirds, however, the data suggest that the interference of other harmonics plays a role as well. In Experiment 4, attempts were made to answer the second and third questions: In supraliminal conditions, both the dominantly perceived beat frequency and the perceived beat strength were determined for various spectral conditions and degrees of tempering. For both the fifth and the major third and for all spectral conditions, the dominantly perceived beat frequency was in most cases equal to the frequency difference of the first pair of adjacent harmonics. Comparison of the DTs and the perceived strength of the beats for corresponding spectral conditions revealed that, especially for the fifth, perceived strength of beats and sensitivity to moderately tempered intervals are highly correlated.