Am. Crawford et Ae. Hay, DETERMINING SUSPENDED SAND SIZE AND CONCENTRATION FROM MULTIFREQUENCYACOUSTIC BACKSCATTER, The Journal of the Acoustical Society of America, 94(6), 1993, pp. 3312-3324
An inversion algorithm for extracting suspended sand size and concentr
ation from simultaneous backscattered acoustic pressure amplitude at t
hree operating frequencies is presented. The algorithm is based on the
differences in signal amplitude between different frequency pairs, an
d is tested using laboratory measurements of multifrequency backscatte
r from a turbulent sediment-carrying jet. Concentration and size profi
les inverted from field and laboratory data are compared with results
from a previously developed algorithm based on signal ratios. The diff
erence inversion scheme is less sensitive to errors arising from low s
ignal levels, allowing the size/concentration measurement range to be
extended to regions of lower concentration. The concentrations from th
e field data agree well with independent optically determined estimate
s. The results demonstrate sensitivity to the backscatter form factor.