The effect of fluid loading on acoustic pressure measurements near structures

Some of the difficulties encountered in underwater sound pressure measurements near structures are discussed. A computation is made of the sound field generated by a monopole acoustic source in the vicinity of an infinite thin elastic plate. To demonstrate the effect of fluid loading on pressure measurements, results are given for the upper half-space above the plate filled, alternately, with air and water, while a vacuum fills the lower half-space. Computed results for this model indicate that no energy bearing acoustic field can be propagated near an elastic plate when fluid loading is heavy. In such circumstances, sound pressure measurements near structures in air are not analogous to measurements that would obtain in water.