The problem of scaling the central effect of auditory stimulus intensity,I(in power units), is considered, and it is argued that there need not be a unitary neurophysiological correlate for “loudness.” Different psychophysical tasks may draw on different central measures of stimulus intensity. A “metric dimension,”L, which the subject may use in making quantitative judgments, is distinguished from a more peripheral “discriminal dimension,”E, involved in the immediate processing of the stimulus input. Binaural intensity summation data are used to derive the form of the function relatingEtoI, and it is shown that for any particular range of intensities this can be approximated by a power function,E = kIn, where the exponentndepends on the range of intensities used, approximating one near the absolute threshold and decreasing as over all intensity increases. On the assumption that with binaural stimulation the over‐all loudness is determined by the sum ofELandER, the effects produced by the stimuli to the left and right ears, linear equiloudness curves are obtained.