As. Schaafsma et Ae. Hay, ATTENUATION IN SUSPENSIONS OF IRREGULARLY SHAPED SEDIMENT PARTICLES -A 2-PARAMETER EQUIVALENT SPHERICAL SCATTERER MODEL, The Journal of the Acoustical Society of America, 102(3), 1997, pp. 1485-1502
Results are presented from an acoustic attenuation spectroscopy study
of suspensions of irregularly shaped sediment particles and of nominal
ly spherical lead-glass beads. The measured spectra cover a wide frequ
ency band of 1-100 MHz. It is shown that the spectra can be brought in
to close agreement with the rigid movable sphere model using two equiv
alent sphere size parameters. One parameter is the diameter d(G) of an
equal cross-sectional area sphere, and is used to scale the frequency
to obtain the nondimensional size/frequency parameter ka. The other p
arameter is the diameter d(p) of an equal volume sphere, and is used t
o scale the particle volume to obtain the particle number density N. I
t was observed that for the irregular particles the attenuation for ka
> 1 is enhanced with respect to the sphere case. The observed enhance
ment factors are considerable: up to 1.6 for natural sand particles an
d 1.8 for the most irregular particles studied (ground quartz). In ter
ms of the two-parameter model the enhancement factor is equal to a sha
pe parameter b(0) = (d(G)/d(p))(3) and can indeed be explained as a sh
ape effect. The implications of this result for the acoustic detection
of suspended sediments in aqueous environments are discussed. (C) 199
7 Acoustical Society of America.