Laboratory studies of near-grazing impulsive sound propagating over rough water

Abstract

Acoustic impulses due to an electrical spark source (main acoustic energy near 15kHz) have been measured after propagating near to the water surface in a shallow container resting on a vibrating platform. Control of the platform vibration enabled control of water wave amplitudes. Analysis of the results reveals systematic variations in the received acoustic waveforms as the mean trough-to-crest water wave amplitude is increased up to 7mm. The amplitudes of the peaks corresponding to specular reflections are reduced and the variability in the tails of the waveforms is increased.

Dynamically Rough Boundary Scattering Effect on a Propagating Continuous Acoustical Wave in a Circular Pipe with Flow

“…The following empirical relation between the normalized standard deviation in the acoustic wave envelope and the normalized free surface roughness height standard deviation can be proposed by which exhibited a fit of R 2 = 0.85, where R 2 is the coefficient of determination. Similar to the results obtained in some other experimental studies where the pulse signal was used (e.g., [ 4 , 5 , 15 ]), the fluctuations in the acoustic wave envelope were found to increase with the increased fluctuations of the dynamic roughness of the water surface waves.…”

“…There is a general lack of evidence on the relationship between the airborne acoustic field in a partially filled pipe and the behaviour of the free water surface of the hydraulic flow in the presence of discrete bed roughness. Theories exist for sound propagation in the presence of a rough boundary [ 1 , 2 , 3 , 4 , 5 ], but not for a partially filled round pipe in which the flow surface is dynamically rough. To the best of the authors’ knowledge, there has not been any experimental work on sound propagation in a partially filled pipe with a dynamically rough flow surface.…”

“…[ 2 ] is relevant to sound propagation in a circular waveguide with static roughness; Ref. [ 3 , 4 , 5 ] are relevant to outdoor sound propagation in the presence of a rough impedance ground.…”