Browsing by Subject "pitch"

Now showing 1 - 3 of 3
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    Perception and Processing of Pitch and Timbre in Human Cortex
    (2018-04) Allen, Emily
    Pitch and timbre are integral components of auditory perception, yet our understanding of how they interact with one another and how they are processed cortically is enigmatic. Through a series of behavioral studies, neuroimaging, and computational modeling, we investigated these attributes. First, we looked at how variations in one dimension affect our perception of the other. Next, we explored how pitch and timbre are processed in the human cortex, in both a passive listening context and in the presence of attention, using univariate and multivariate analyses. Lastly, we used encoding models to predict cortical responses to timbre using natural orchestral sounds. We found that pitch and timbre interact with each other perceptually, and that musicians and non-musicians are similarly affected by these interactions. Our fMRI studies revealed that, in both passive and active listening conditions, pitch and timbre are processed in largely overlapping regions. However, their patterns of activation are separable, suggesting their underlying circuitry within these regions is unique. Finally, we found that a five-feature, subjectively derived encoding model could predict a significant portion of the variance in the cortical responses to timbre, suggesting our processing of timbral dimensions may align with our perceptual categorizations of them. Taken together, these findings help clarify aspects of both our perception and processing of pitch and timbre.
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    Perception of complex sounds at high frequencies
    (2022-05) Guest, Daniel
    Understanding how the auditory system processes frequency and intensity information is crucial to our understanding of overall auditory function. Although great progress has been made in understanding this issue in the case of simple sounds, such as pure tones, considerable uncertainty remains in understanding how the auditory system processes frequency and intensity information in more complex and naturalistic sounds. Moreover, much of our understanding comes from sounds in the low-frequency range, where phase locking to temporal fine structure is available in the auditory nerve. To address these limitations, this dissertation first presents new data on a variety of psychoacoustical tasks measuring frequency and intensity perception not only at low frequencies but also at high frequencies. Next, the psychophysical results are interpreted with the aid of modern computational models of the auditory system, which capture key features of the complex and nonlinear processing that takes place in the auditory periphery and auditory subcortex. Both the behavioral and computational results demonstrate how perception of complex sound features, such as pitch and spectral shape, reflects a delicate combination of both low-level constraints imposed by peripheral encoding of sound and higher-level influences, such as central processing, familiarity, and context.
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    Perception of multiple pitches: Sequential and simultaneous pitch relationships
    (2018-01) Graves, Jackson
    The perception of pitch, a dimension of sound that is important for music perception, speech perception, and sound source segregation, is influenced by its context, both sequential and simultaneous. In music, pitch sequences form melodic contours, and simultaneous pitches form chords and harmony. A series of experiments investigated the perception of melodic contour in pitch as well as two other auditory dimensions, brightness and loudness. The results showed that subjective ratings of continuation for brightness and loudness sequences conformed to the same general contour-based expectations as pitch sequences, suggesting that melodic expectations are not unique to the dimension of pitch. Listeners with congenital amusia, however, exhibited less impairment on a short-term memory task for loudness contours than for pitch contours, suggesting a pitch-specific deficit. In a pair of experiments, priming of a familiar tonal context improved accuracy on a pitch interval discrimination task. However, the overall benefit to performance from tonal context was small, suggesting that previously reported effects of response time may mainly reflect expectancy as opposed to perceptual accuracy. In the last series of experiments, listeners accurately identified pitches in mixtures of three concurrent complex tones, despite poor peripheral resolvability. These stimuli help to dissociate two normally confounded variables in complex pitch, harmonic number and peripheral resolvability. The results were compared with outputs from two kinds of auditory models, one based on the rate-place code for pitch and the other based on the temporal code. Overall, these findings suggest that pitch perception involves bottom-up integration of both spectral and temporal information, as well as top-down effects of learning and context.