Real‐ear responses of circumaural, supra‐aural, and insert earphones

Abstract

Circumaural earphones provide improved coupling when compared with the standard supra‐aural audiometric earphone (TDH 39, 49) [Kruger et al., J. Acoust. Soc. Am. 67, S91 (1980); Villchur, ibid. 48, 1387–1396 (1970); Erber, ibid. 44, 555–562 (1968); Shaw, ibid. 39, 471–479 (1966)]. The variability of real‐ear responses of the TDH‐49 earphone, audiometric circumaural earphones (Villchur‐Telephonics Model 566, Beltone Auraldome & Audiocap), a hi‐fi circumaural earphone (Sennheiser HD 430) and an insert phone (Knowles BP 1869) was assessed. Probe microphone frequency response measurements in the ear canal were used to evaluate intrasubject and intersubject variability with the above transducers (10Ss: 5♂, 5♀ 5 repetitions/condition: transducer, subject versus experimenter placement) and were referred to either the diffuse field or the tympanic membrane. Real‐ear response variability is contrasted with KEMAR response variability [Kruger et al., (1980); Ciechanowski and Cooper, J. Am. Aud. Soc. 2, 88–94 (1976)] and with coupler calibration variability appropriate to the transducer (NBS 9‐A coupler, Penn State flat plate coupler, Zwislocki coupler). The nature of the variations in real‐ear responses with these supra‐aural, circumaural, and insert earphones will be discussed in terms of calibration, probe microphone placement, coupling to the head, and earphone placement. [Work partially supported by AOS.]