Infrapitch echo

A noise mixed with its repetition after a delay of t sec can produce a pitch corresponding to 1/t. The accepted range of this echo pitch is about 50 through 2000 Hz (t from 0.02 through 5×10⁻⁴ sec). Evidence is presented suggesting that temporal analysis should permit detection of echo repetition well below the pitch limit of t=0.02 sec. In keeping with predictions, we found that listeners could detect the delay of echo repetition for noise down to at least t=0.5 sec (periodicity of 2 Hz). While polarity inversion of the echo alters apparent frequency at delays producing pitch, such inversion has no effect on apparent frequency of infrapitch echo. It is suggested that echo detection within the pitch range involves both a neural place analysis of the rippled power spectrum and a concurrent neural temporal analysis insensitive to polarity inversion; echo detection in the infrapitch range cannot employ neural place cues and is based solely upon a polarity‐insensitive temporal analysis. Infrapitch repetition is discussed as a tool for investigating temporal domain analysis free from concurrent frequency domain analysis.