Evidence for a cancellation tooth in the absence of a harmonic partial.

Detection of a target sound (e.g., a voice) is often better in a background of harmonic than inharmonic tones. This difference has been attributed to harmonic cancellation, a mechanism that integrates masker's fundamental frequency (F0) information across channels to inhibit neural responses at the F0 rate. Here, we questioned whether this mechanism would apply within an auditory channel in which a (single) harmonic partial was missing. In three different spectral regions (300-500; 900-1100; 2500-2700 Hz), we measured masked detection threshold (MDT) for a narrow noise band target against harmonic or inharmonic complexes, based on 200 Hz F0. As expected, MDTs were generally lower in harmonic than inharmonic maskers, although the effectiveness and precision of the cancellation were diminished relative to a more traditional design (with no missing partial). But remarkably, MDTs were higher in the harmonic than inharmonic masker when the target center frequency matched the position of the missing partial, suggesting that the target was hindered by cancellation of the harmonic frequency (400, 1000, or 2600 Hz) even in the absence of masker energy at this frequency. The mechanism of harmonic cancellation does not rely (at least not greatly) on the local excitation induced by the masker.