THE IMPORTANCE of routine calibration of earphones and bone-conduction receivers used with audiometers cannot be too highly emphasized. Otherwise, it is impossible: (1) to know whether thresholds of patients are contaminated by faulty equipment; (2) to know whether apparent changes in hearing over time for a patient are due to true differences in his performance or to variations in the equipment; and (3) to accurately compare results obtained in one clinic or laboratory with those found in another clinic or laboratory.
Earphone Calibration
The methods of calibrating earphones have been fairly well established and reported in the literature.1-3 Several types of artificial ears are available commercially for calibrating earphones. In our laboratory, we prefer an artificial ear complement (Bruel & Kjaer) consisting of a standard artificial ear and 6 cc coupler, condensor microphone, and spectrometer, which enables us to determine the performance of audiometers or earphones and to note