Effect of air bubbles in the external auditory meatus on underwater hearing thresholds.

Abstract

Thresholds of human hearing were obtained underwater for two conditions: (1) with the external auditory meatus completely water filled and (2) with a bubble of air trapped against the tympanic membrane. The first condition was accomplished by forcibly irrigating the external meatus underwater the second, by placing plugs in the ears in order to encapsulate air in the meatus until the head was underwater and the test with the plugs removed) initiated. Subjects were seven divers who were tested in DICORS at a depth of 12 ft; threshold SPLs were obtained free field by a modified Békésy technique for the frequencies 125 Hz, 250 Hz, and 1, 2, and 8 kHz. Threshold shifts (re air) for both conditions of underwater hearing were consistent with those previously reported. SPLs for the two experimental conditions were virtually identical for all frequencies except 250 Hz, where hearing was 6 dB better for the water-filled meatus condition. Apparently, the presence or absence of air bubbles in the external meatus contributes little if anything to underwater hearing thresholds.