Fusion of auditory components: effects of the frequency of amplitude modulation

The fusion of two amplitude-modulated (AM) tones presented simultaneously was studied. Subjects were presented with an AM tone (A) followed by a copy of itself (B) which was accompanied by another AM tone (C). In different experiments, the subjects were asked either to rate how clearly they could hear Tone B in the BC mixture or whether Tone B was present or not. The stronger the fusion of Tones B and C, the harder it was to "hear out" Tone B. It was found that fusion was strongest when Tones B and C were modulated at the same rate; segregation curves were obtained for the degree of mismatch of modulation frequency.