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Evidence for a common pitch processor for the perception of the residue pitch from binaural and diotic components
Authors:
GOCKEL, H., CARLYON, R.P., & Plack, C. J.
Reference:
International Journal of Audiology, 49 (9), 711-712.
Year of publication:
2010
CBU number:
7173
Abstract:
This study investigated whether the processes determining the residue pitch of a harmonic complex tone can combine a component pitch derived solely from binaural interaction (Huggins pitch) with a component pitch for which no binaural processing is required. In a two-alternative forced-choice task, subjects indicated which of two complex tones had the higher pitch. Complex tones consisted of two “harmonics”, and had a fundamental frequency of 400 Hz (1st and 2nd harmonics at 400 and 800 Hz), 266.7 Hz (2nd and 3rd harmonics at 533.3 and 800 Hz), or 160 Hz (4th and 5th harmonics at 640 and 800 Hz). Each stimulus was compared with each other. The lower and upper harmonics were, respectively: (i) both Huggins pitches; (ii) both narrowband noises; iii) a Huggins pitch and a narrowband noise; (iv) a narrowband noise and a Huggins pitch. Stimuli were derived from 500-ms diotic Gaussian noises, lowpass filtered at 2-kHz, presented with an rms level of 68 dB SPL. Huggins pitches were created using linear phase transitions (0 to 2Pi) in one channel, and narrowband noises were added diotically, resulting in increases in spectrum level of 6 dB. The phase transitions or narrowband noises extended from -3% to +3% of the center frequency of a harmonic. When the harmonics were either both narrowband noises or both Huggins pitches (“single mode” control conditions), 10 out of 15 subjects mostly perceived the residue pitches of the complexes rather than the component pitches, i.e., they listened synthetically rather than analytically. This was indicated by the finding that, for a given pair of harmonics, they consistently judged the complex with the higher F0 as higher in pitch even though the lower harmonic of that complex had a lower frequency. Importantly, their response pattern was not significantly different in the “mixed-mode” conditions, where a Huggins-pitch harmonic was combined with a narrowband-noise harmonic. In other words, the mixed-mode harmonics were equally likely to lead to the perception of a residue pitch as the single-mode harmonics. The results indicate that the mechanism which derives residue pitch does not differentially process component pitches of different origin (whether or not they require binaural processing). This supports the idea that there exists one single mechanism for the derivation of residue pitch from binaural components and from spectral components, and that this mechanism operates at or after the level of the medial superior olive.