Pure-Tone Equal Loudness Contours for Standard Tones of Different Frequencies

Abstract

Subjects (14 high-school students) made judgments of equal loudness by adjusting the intensity of comparison tones of ten different frequencies. The comparison tones were presented diotically alternately with standard tones (1-sec duration each). Each standard tone remained fixed at one frequency (125, 1000, or 8000 Hz) and one intensity (10, 20, 40, or 70 dB sensation level) while the data were collected for any single equal loudness contour. In this manner, families of equal loudness contours were generated for each of the three standard frequencies. The contours at 1000 Hz were compared with those for 1000 Hz in the literature. The contours for 125 and 8000 Hz, determined by otherwise using the same algorithm, were different in shape from the 1000-Hz set as well as from each other. These differences implied a violation of the transitivity assumption in the loudness calculating algorithm. Tests for transitivity among the three standard frequencies failed in many cases.