Comments on 'Effect of Air Bubbles in the External Auditory Meatus on Underwater Hearing Thresholds' [H. Hollien and J. F. Brandt, J. Acoust. Soc. Amer. 46, 384-387 (1969)].

The loss in acuity which occurs when ears are submerged underwater has been computed using equivalent circuit analysis for the completely filled ear canal and for the canal containing a trapped air bubble at the eardrum. Contrary to popular misconception, the bubble is, if anything, beneficial, not detrimental. This may explain the recent findings of Hollien and Brandt [J. Acoust. Soc. Amer. 46, 384-387 (1969)], who measured no significant difference in underwater thresholds with and without bubble and regarded this as evidence that the middle-ear mechanism is not functionally operative in underwater hearing. Their contention is not supported by the present analysis. The computed differential loss between aerial and underwater tympanic transmission shows a frequency-dependent function, which resembles Hollien's measurements, but with 10-15-dB smaller magnitudes. Various hypotheses relating to this difference still need to be investigated; however, the predicted frequency dependence of the loss lends strength to previous observation [B. B. Bauer and E. L. Torick, J. Acoust. Soc. Amer. 39, 35-39 (1966)] that a rising pressure-frequency response near the external auditory meatus is needed to produce a normal-sounding underwater earphone. [ABSTRACT FROM AUTHOR]