Browsing by Subject "Auditory grouping"

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    Effects of timing and context on pitch comparisons between spectrally segregated tones.
    (2011-12) Borchert, Elizabeth Marta Olsen
    Pitch, the perceptual correlate of fundamental frequency (F0), is an important cue for understanding aspects of both music and speech. Much research has been devoted to pitch, with most being dedicated to measuring listeners' ability to judge pitch differences between sounds that are otherwise identical. However, in the natural environment, pitch comparisons are often made between different speech sounds (or different musical instruments), which differ not only in pitch but also in timbre. This dissertation investigates factors that affect normal-hearing listeners' ability to perceive and discriminate pitches of tones that differ in timbre due to being filtered into segregated spectral regions. The first study shows that the timing of tone presentation affects discrimination ability: listeners have difficulties comparing the F0s of sequentially presented sounds, and are much better able to perform the task when the tones are presented simultaneously. A follow-up experiment reveals that rather than explicitly comparing F0s, listeners seem to use a perceptual fusion cue when the tones are presented simultaneously; performance worsens when perceptual fusion is disrupted by asynchronous presentation or by auditory stream segregation induced with captor tones. A further study reveals that listeners' difficulty comparing sequentially presented tones of different timbres persists despite intensive training, and that individual differences in sequential tone discrimination cannot be reliably predicted based on musical experience or on analytical versus synthetic listening mode. Since pitch comparisons often occur within a musical context, the remainder of the thesis investigates the effect of a musical context on sequential pitch discrimination. Regardless of the predictability of the brief context, pitch discrimination generally improves for targets presented following a melodic context that establishes a tonal center corresponding to the pitch of the target tone. This effect of tonality is stronger for discrimination of different-timbre tone pairs than for same-timbre tone pairs. One interpretation of these findings is that sequential different-timbre pitch discrimination is limited more by cognitive factors, which are influenced by tonal context, than is same-timbre discrimination. The interactions between pitch, timbre, and context described in this thesis provide challenges for our understanding of how we perceive pitch in complex listening situations.