Matching functions and equal-sensation contours for loudness.

Loudness balances were collected from three subjects, employing 57 combinations of 13 frequencies extending from 20 to 5000 cps. Determinations were made from levels close to threshold to the highest levels tolerable by the subjects, with 5‐dB intervals. Stimuli were applied by an earphone through individually moulded ear inserts, and were measured in decibels sound‐pressure level a few millimeters from the eardrum. For each subject, a symmetric and transitive subset of the data was employed for constructing a set of matching functions and a set of equal‐loudness contours. Matching functions generally were linear, or showed a double inflection (in log‐log coordinates). Equal‐loudness contours generally agree with previous determinations, but show a steeper rise towards low frequencies; below 300 cps, and at medium levels, the contours approach straight lines with a slope of −40 dB/decade. Obtained matching functions are compared to three sets of theoretical functions, favoring the matching functions deriv...