The role of resolved and unresolved harmonics in pitch perception and frequency modulation discrimination

Abstract

A series of experiments investigated the influence of harmonic resolvability on the pitch of, and the discriminability of differences in fundamental frequency (F0) between, frequency-modulated (FM) harmonic complexes. Both F0 (62.5 to 250 Hz) and spectral region (LOW: 125-625 Hz, MID: 1375-1875 Hz, and HIGH: 3900-5400 Hz) were varied orthogonally. The harmonics that comprised each complex could be summed in either sine (0 degree) phase (SINE) or alternating sine-cosine (0 degree-90 degrees) phase (ALT). Stimuli were presented in a continuous pink-noise background. Pitch-matching experiments revealed that the pitch of ALT-phase stimuli, relative to SINE-phase stimuli, was increased by an octave in the HIGH region, for all F0's, but was the same as that of SINE-phase stimuli when presented in the LOW region. In the MID region, the pitch of ALT-phase relative to SINE-phase stimuli depended on F0, being an octave higher at low F0's, equal at high F0's, and unclear at intermediate F0's. The same stimuli were then used in three measures of discriminability: FM detection thresholds (FMTs), frequency difference limens (FDLs), and FM direction discrimination thresholds (FMDDTs, defined as the minimum FM depth necessary for listeners to discriminate between two complexes modulated 180 degrees out of phase with each other). For all three measures, at all F0's, thresholds were low (< 4% for FMTs, < 5% for FMDDTs, and < 1.5% for FDLs) when stimuli were presented in the LOW region, and high (> 10% for FMTs, > 7% for FMDDTs, and > 2.5% for FDLs) when presented in the HIGH region. When stimuli were presented in the MID region, thresholds were low for low F0's, and high for high F0's. Performance was not markedly affected by the phase relationship between the components of a complex, except for stimuli with intermediate F0's in the MID spectral region, where FDLs and FMDDTs were much higher for ALT-phase stimuli than for SINE-phase stimuli, consistent with their unclear pitch. This difference was much smaller when FMTs were measured. The interaction between F0 and spectral region for both sets of experiments can be accounted for by a single definition of resolvability.

Concurrent Sound Segregation in Electric and Acoustic Hearing

“…Overall, it seems that differences in F0 have a strong effect on concurrent sound segregation only when conveyed by resolved harmonics in NH. This could be simply because such harmonics produce a stronger pitch percept than other sounds (Hoekstra 1979;Houtsma and Smurzynski 1990;Shackleton and Carlyon 1994;Gockel et al 2004), or perhaps because the auditory system exploits a deviation from spectral regularity, which does not occur when F0 differences are encoded purely by the temporal response of the AN (Roberts 2005).…”

Properties of auditory stream formation

“…started at a positive-going zero-crossing. This leads to a waveform with two major peaks per period (figure 3, middle trace); the resulting sound has a clear pitch, which is roughly one octave higher than for tone C [55,56], and a less 'buzzy' timbre. Finally, a tone R had harmonics added in random phase, which leads to a more noise-like quality and a less clear pitch (figure 3, bottom trace).…”

Neural Sensitivity to Periodicity in the Inferior Colliculus: Evidence for the Role of Cochlear Distortions

“…Mechanisms that account for temporal pitch have been the subject of numerous psychophysical (Krumbholz et al 2000;Plack and White 2000;Shackleton and Carlyon 1994;Wiegrebe et al 1998) and modeling (de Cheveigne 1998;Meddis and O'Mard 1997) studies, and electrophysiological investigations in experimental animals (Biebel and Langner 2002;Cariani and Delgutte 1996a,b;Wiegrebe and Winter 2001). A number of models posit mechanisms that could account for the processing of temporal pitch cues, in particular the implementation of auto-correlation on the stimulus waveform (de Cheveigne 1998;Licklider 1951).…”