Abstract: The sensitivity of the earphones used in the hearing tests carried out by the Institute of Psychology is determined by measuring the sound pressure produced by them both at the external. end of the meatus of the human ear and at the eardrum, for which purpose a probe microphone is employed. From the earphone sensitivity data and the audiometric data the normal threshold of hearing for 9 different frequencies (from 125 to 8000 inclusive) was obtained.The threshold curves were compared with curves obtained by different authors abroad.

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