Pitch discrimination with harmonic and inharmonic tone complexes

The measurement of sensitivity to temporal fine structure (TFS) in listeners can be measured by using a linear frequency-shift of a harmonic tone complex. However, the linear frequency shift of the harmonic tone complex breaks the harmonic structure, introducing a harmonic-inharmonic cue in addition to the pitch shift. In the present study, we investigated the relative contributions of frequency shift and harmonicity in normal-hearing listeners, using harmonic-harmonic, harmonic-inharmonic, and inharmonic-inharmonic shifts for unresolved tone complexes. A two-down-one-up adaptive method was used to measure the frequency shift threshold. Our results show that both inharmonic variants of the frequency shift have lower detection thresholds than the harmonic-only shift. The two inharmonic conditions are not different, indicating that the linear shift threshold is not driven by a harmonic-inharmonic cue. The effect is the same for all frequencies tested here. The results are discussed in relation to both excitation pattern and temporal fine structure models.