Proposed Laboratory Standard of Normal Hearing

Abstract

The present study was performed to determine the normal monaural threshold of hearing by earphone listening for 3 groups of otologically normal subjects ranging in age from 18 to 24 years. All subjects were screened for a life history of minimal exposure to noise and the absence of active military service. Threshold determination from 128 to 11,584 cps were made with 2 types of earphones calibrated in a National Bureau of Standards coupler. For each of 2 groups of subjects, threshold tests were made following slightly different modifications of the method of limits with 5 db steps; the third group was tested with still another modification using 2 db steps. The results of the study showed significant differences between earphones, as well as between male and female subjects. Some consideration was given to the problem.of redefining the normal zero reference for audiometers and some tentative suggestions were made. The findings of the present study are offered for consideration as proposed normal standards of hearing for pure tones for individuals, 18 to 24 years of age, who show no evidence of otological disorders and have a life history of minimal exposure to noise.