Empirical Determination of Air-Water Impedance Differences in Small Tanks

Abstract

Airborne sonic pressure in an open or sealed housing enclosing an aquarium was measured in the air and in the water. Effective impedance differences were 9.1 dB with the housing open and 4.5 dB with the housing sealed. Both conditions indicated an effective impedance difference considerably less than the 35.5 dB impedance difference between air and the open ocean. Prevalent use of sonic fields in small aquariums thus require detailed calibration of sonic fields in tanks where the air-water interface is tranversed. The middle ear apparently functions primarily to transduce airborne sonic pressure into displacement in the cochlear fluids, rather than to match sonic pressure impedance.