Abstract:
The purpose of this study is to investigate if coherent frequency modulation by itself can induce auditory streaming when there are no harmonicity cues. A signal tone was presented with a complex of tones whose frequency fluctuated. To separate the effects of frequency modulation from those of harmonicity, components of the masker were not spaced by a fixed frequency distance but by a critical bandwidth. The detection threshold of the signal was tested in two conditions. In the first, called the coherent condition, all components of the masker were modulated coherently. In the second, incoherent condition, the masker was divided into two parts, the on-signal part and the flanking part. The on-signal part was the bandpass filter of the complex that was centered on the signal frequency and the flanking part was the rest of it. To make the modulation incoherent, the flanking part was moved forward or backward by half a cycle of modulation. The signal was detected with less difficulty in the coherent condition, indicating that the components with coherent frequency modulation were integrated even if they were inharmonic.