The effect of frequency tolerance on audiometer accuracy.
Investigations into the methods used to calibrate audiometers reveal that the 6 000 Hz frequency is particularly liable to yield inconsistent results when calibrated in the usual way. It is shown that the TDH39 telephone receiver which is usually calibrated on a 9A coupler in accordance with the International Standards Organization recommendation R389 will depend to a considerable extent on the precise frequency used and may differ by as much as 7 db when the frequency is varied but still retained within the specified tolerance limits. A new telephone receiver, the TDH50, is much less sensitive to frequency variation. It is shown that this receiver should be calibrated with the same threshold figures as the TDH39.
D001299:Audiometry / Q000295:instrumentation / Q000592:standards*; D004431:Ear, External / Q000032:analysis; D006801:Humans; D013016:Sound; D013689:Telephone