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Unformatted text preview: Chapter 7: Introduction to Psychoacoustics Psychoacoustics a branch or psychophysics that deals with the quantification of sensation and the measurement of the psychological correlates of the physical stimulus; the study of the psychological response to acoustical stimulation 1. The Concept of Threshold o Concept of threshold implies the existence of a discrete point along the physical continuum of the stimulus Such as its intensity above which an organism always responds to the stimulus and below which it never does Such a discrete point is difficult to demonstrate empirically by virtue of the influence of various internal and external events: External events: environmental noise, small but finite fluctuations in the stimulus magnitude attributable to instrumentations or procedural limitations Internal events: noise in the nervous system and variations in the experimental subjects state or level of attention over time or even the subjects wellbeing o Threshold is likely to vary from moment to moment Best measure is to sample responses repeatedly and treat the data statistically to yield a threshold estimate o Absolute Threshold is a statistic defined as the value of the stimulus magnitude that, on average, elicits the desired response a specified percentage of the time that the stimulus is presented Level at which the sound is heard 50% of the time that it was presented Above this magnitude the subject responds more frequently to the stimulus Below this magnitude the subject responds less frequently to the stimulus o Threshold is a value that divides the range of the stimulus magnitude into regions of relatively high versus low probabilities of response o Uncontrolled variables can affect the accuracy of threshold measurement Sound-treated booths are an example of how the effects of extraneous variables can be minimized o Modern psychophysicists question the validity of the threshold concept Mainly due to internal noise in the nervous system caused by spontaneous random neural discharges How the subject is instructed to respond also affects the measured threshold values o Threshold measurement is a valuable psychophysical research and clinical tool that provides one measure of the capabilities of a sensory system o Even though there is inherent variability in the threshold measurement, reasonably reproducible threshold measurements can be obtained on humans and animals o Thresholds can be determined within certain limits of confidence that are acceptable for practical purposes 2. The Auditory Response Area o It is useful to map out the physical domain of hearing using the absolute threshold of hearing and related measures as the descriptors o The level of a tone at one frequency is then varied in increasing and decreasing steps until the threshold at that frequency is found o Other frequencies of the test stimulus are then presented to the subject until his or her absolute thresholds are obtained at a...
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This note was uploaded on 05/18/2011 for the course CSD 1025 taught by Professor Durrant during the Spring '11 term at Pittsburgh.
- Spring '11