R. C. Bilger
K. L. Brestal
J. M. Lesniak
K. L. Petrow
T. A. Meyer
Dept. of Speech and Hear. Sci., Univ. of Illinois, 901 S. Sixth St., Champaign, IL 61820
The purpose of the present study was to investigate the possibility that the low-frequency leakage of sound from beneath supra-aural earphone cushions increases as adults age, giving the appearance of a low-frequency hearing loss. The subjects were four groups (n=6) defined by age (younger than 30 and older than 65 years) and gender. The probes for ER-7C microphones were placed 0.5 in. into each of a subject's ear canals. Continuous pure tones at 11 1/3-oct frequencies (100--1000 Hz) were presented via TDH-39 headphones mounted in MX-41/AR cushions. Tones were presented at 80 dB SPL. The procedure was replicated once. The variable analyzed was the difference between sound pressure level measured in the ear canal and that measured in an NBS 9A coupler. The low-frequency leak was present in our results in that the average leak increased at a rate of 12 dB/oct, beginning at 400 Hz. The slope of the leak, however, was different for right and left ears and was different for the four age-by-sex groups. These results strongly suggest that caution be used in interpreting sensitivity differences obtained with supra-aural earphones. [Work supported by DC00174. Etymotic Research loaned us one of the two ER-7 microphones used.]