The perceived pitch of synthesized vowels with alternate pulse cycles

Speech with alternate pulse cycles (APC), also known as diplophonia, double pulsing, etc., often brings problems to pitch determination algorithms. Although this phenomenon has been studied in light of nonlinear theory recently, to date, no study has been done to measure the perceived pitch of speech with APC. In the present study, a perception experiment was conducted to investigate the perceived pitch of speech with APC. Two synthetic vowels, /a/ and /i/, with fundamental frequencies at 140 and 220 Hz, both amplitude and frequency modulated, respectively, were used as stimuli. The modulation levels ranged from 0 to 0.9. The subjects were asked to judge the pitch of modulated vowels in reference to the synthetic vowels without modulation. The results show that the modulation level affects the perceived pitch in a nonlinear manner, and frequency modulation seems to have greater effects on the perceived pitch than amplitude modulation. In addition, different fundamental frequencies have different effects o...