Quantification of Loudness

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. University of Illinois Press is collaborating with JSTOR to digitize, preserve and extend access to The American Journal of Psychology.The present study employed 600 subjects and extended earlier experiments under 'ideal' conditions to white noise. When known experimental biases were eliminated, half loudness was equal to half sound-pressure level (-6 dB) from 45 through 90 dB. The same simple relation held whether stimulation was through headphones or loudspeaker, and whether responses were numerical estimates or marks on a linear loudness scale. These findings and other evidence support the physical-correlate theory of sensory intensity and suggest that quantitative estimates of sensation are based not on the quantitative nature of sensory events as such but rather on the external events and relations they signify.When asked to judge the intensity of sensation, subjects do so with a fair degree of agreement for any given set of conditions. How is this accomplished? Do they sense directly the amount of neural excitation? Or do they estimate physical values associated with the stimulus?Patterns of neural input from our exteroceptors normally signify conditions in our environment. They are evaluated by our central nervous system, not as signals describing internal physiological events, but rather as signals describing external events associated with this neural input. This compelling association of sensory patterns with stimulus characteristics has led to the theory that estimates of sensory magnitudes (and the derived sensory scales) are based on estimates of physical magnitudes. It follows that if a certain percentage of the stimulus intensity is judged to be half subjective magnitude at one level, the same percentage should be judged half subjective magnitude at other stimulus levels (Warren, 1958). Stated as a general rule, this 'physical-correlate theory' requires that equal stimulus ratios produce equal subjective ratios. Experimental data fitting this rule have been used to derive a psychophysical power function (Plateau, 1872; Stevens, 1959).In addition to providing an explanation for the empirical psychophysical power law, the physical-correlate theory leads to quantitative predictions for individual modalities. Confirmation of such predictions has been reported for a number of sensations other than loudness (see Warren and Warren, 1956;Warren, 1958;Warren, 1969). PM All use subject to JSTOR Terms and Conditions WARREN Loudness judgments are considered by this theory to derive from the ability of listeners to estimate the changes in stimulation associated with changes in distance, so that half loudness should be equivalent to estimates of doubling distance from the soun...

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