ON THE PERCEPTUAL LIMITS OF OCTAVE HARMONY AND THEIR ORIGIN

Three subjects were monaurally presented with dyads of simultaneous, frequency modulated, sine tones approximately 1 oct apart. The tones, with carrier frequencies F(L) and F(H), were presented in a background of pink noise and at a low sensation level, so that they were completely resolvable by the subjects' peripheral auditory filters. In two experiments, subjects had to judge on each trial which of two dyads was inharmonic (F(H) not-equal 2F(L)); the relative mistuning of the inharmonic dyad [(F(H) - 2F(L))/2F(L)] was varied independently of F(L) and could be either positive or negative; F(L) was fixed within trials in one experiment, and varied within trials (from about 8%-20%) in the other experiment. In both experiments, performance monotonically worsened as F(L) increased from 300-2000 Hz; in addition, negative mistunings were more often identified as inharmonicities than positive mistunings. In another experiment, a 41-2AFC procedure was used to assess the detectability of changes in F(H), irrespective of their effect on the perception of harmonicity. Compared to the other two experiments, performance was not the same function of F(L), and was much better at high F(L). Thus it is concluded that the detection of inharmonicity was limited by factors other than those responsible for fine pitch discriminations. Our results also have implications with respect to the origin of human listeners' melodic octave templates.