Fig. 8. (A) Dual biphonation (two-voice phenomenon with biphonation in both voices). The sound at the arrow consists of two fundamental frequencies (f₀ and g₀), both simultaneously modulated by a third frequency (m₀). Although f₀ and g₀ are modulated in opposite patterns in the frequency domain (one downsweeping and the other upsweeping in frequency), the rate of amplitude modulation frequency m₀ is the same (approx. 250 Hz) for both, as evidenced by evenly spaced sidebands the same distance from both f₀ and g₀. (B) An expanded view of the sound waveform showing the pattern of amplitude modulation. (C) Power spectrum taken at arrow a in spectrogram (A). Abbreviations as in Fig. 3.