Title
Effect of wind-generated bubbles on fixed range acoustic attenuation in shallow water at 1-4 kHz
Author
Ainslie, M.A.
TNO Defensie en Veiligheid
Publication year
2005
Abstract
Long-range acoustic propagation in isothermal conditions is considered, involving multiple reflections from the sea surface. If the sea is calm there is almost perfect reflection and hence little loss of acoustic energy or coherence. The effect of wind is to increase propagation loss due to rough surface scattering and the interaction with near-surface bubble clouds. Previously published measurements of wind-related attenuation in shallow water, at a fixed range of 23 km, are converted to surface reflection loss by dividing the total attenuation by the expected number of surface interactions. Theoretical predictions of coherent reflection loss are compared with these measurements in the frequency range 0.9-4.0 kHz and wind speeds up to 13 m/s. Apart from an unexplained seasonal dependence, it is shown that the magnitude of the predicted rough surface scattering loss is sufficient to explain the measurements if the effect of bubbles is included, and not otherwise. The bubbles are found to play an important catalytic role, not by scattering or absorbing sound, but by refracting it up towards the sea surface and thus enhancing the scattering loss associated with the rough air-sea boundary. Possible explanations for the apparent seasonal variations in the measurements are explored. © 2005 Acoustical Society of America.
Subject
Physics
Acoustic wave propagation
Attenuation
Catalysis
Reflection
Surfaces
Water
Wind effects
Acoustic energy
Air sea boundary
Long-range acoustic propagation
Scattering loss
Bubbles (in fluids)
To reference this document use:
http://resolver.tudelft.nl/uuid:feb25069-2f98-4624-81c9-474340f6a928
DOI
https://doi.org/10.1121/1.2114527
TNO identifier
221247
Source
Journal of the Acoustical Society of America, 118 (6), 3513-3523
Document type
article