Subharmonic pitches of a pure tone at low S/N ratio

2AFC scores were obtained on 50 untrained subjects who had to respond to a 3% increment or decrement of the fundamental frequency of two successive signals. The first signal in each trial was a reference, containing six harmonics of 200 Hz. Main variables were the number of harmonics of the second signal in a trial (either 3, 2, or 1) and the presence or absence of continuous background noise. Low scores were observed in the absence of the noise (typically 65% for the 3- and 2-component signals, and virtually 50% for the 1-component signals), whereas in the presence of the noise much higher scores were observed (typically 90% and 80%, respectively). The results indicate that background noise has great impact on the perceptibility of a ’’low pitch’’ related to the fundamental frequency, even more so than the number of components presented (within the range of three, two, or one components): at a low S/N ratio, even a single harmonic may give rise to the perception of a subharmonic low pitch. Subsequent experiments with three trained subjects indicated that this potential of a single pure tone to evoke a subharmonic pitch deteriorates for harmonic numbers of about n=7 to 11. The theoretical implications of these subharmonic pitches of a pure tone to pitch perception in general are discussed. Subject Classification: [43]65.54, [43]65.75, [43]65.35.