Loudness Adaptation for Bands of Noise

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Abstract
Two experiments were done on loudness adaptation for bands of noise. In experiment 1, loudness adaptation for a wide-band thermal noise of 100-5000 cps was studied as a function of 5 sound pressure levels: 40, 70, 90, 100, and 105 db. The mean maximum loudness adaptation obtained was 2.3, 9.9, 11.4, 14.4, and 16.3 db, respectively. The mean standard deviation for all measures was 6.1 db, and the distributions of the sets of measures tended to be skewed toward greater adaptation. In experiment 2, the loudness adaptation for a 1500-cps tone was compared with that for bands of noise whose centers (mel scale) were at 1500 cps, and whose over-all sound pressure levels were equal to that of the pure tone. The band limits in cycles per second were 1280-1720, 1075-1950, 720-2600, and 100-4900. For each band, adaptation was measured for 50, 70, and 90 db. Loudness adaptation for 1500 cps is about 8.5 db greater than the maximum adaptation for any noise band at any sound pressure. Adaptation is small (4.5 db) at 50 db for all bands of noise; it is complete within one min and is about equal for all band widths. At 70 and 90 db, time taken for complete adaptation increases and the two widest bands give greater adaptation than the two narrowest bands. At 90 db a trend becomes clear: the wider the band, the greater the degree of adaptation and the longer the time required for maximum adaptation to be attained.

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