Untitled - Teknik Kelautan / ITB

Application of Cascade Matrix Method on Reflection Coefficient
Prediction of UnderwaterAcoustic for Inclined Seabed
Irsan Soemantri Brodjonegoro1 and Danny Friyadi 2
1 Ocean Engineering Program, Institut Teknologi Bandung
(Email: irsansb@ocean.itb.ac.id)
2 Graduate Student of Ocean Engineering Program, Institut Teknologi Bandung
(Email: dannyf1899@gmail.com)
Abstract. The reflection coefficient of underwater acoustic can be predicted by full
matrix method based on the principle of continuity of pressure and particle velocity
in a fluid (or sediment) boundary. However in the case of propagation through thenlayer
(three layers or more), a full matrix method is in efficient because it involves
inverse matrix with large dimension 2n-2 x2n-2. This paper presents an alternative
method i.e.cascade matrix system to predict reflection coefficient of underwater
acoustic propagating through n-layer media. This method is simpler than full matrix
method because it involves multiplication of transfer matrix with dimension (2x2) in
total of n-2. Simulation results showed that the difference of reflection coefficient
obtained by cascade matrix method and full matrix method was less than10 -4 % for
the acoustic propagation at three, six, and ten-layer media. Application of cascade
matrix method for reflection coefficient can be used to calculate transmission loss
due to bottom reflection. Simulation showed that on underwater acoustic source
located at station GeoB10048-1 travelling to Geob10044-1, at depth of 100 m, two
layers of sediment, and the initial angle-5 o to 5 o , the underwater acoustic intensity
level of source is 169.59dBre 1µ Pa and remaining acoustic intensity level after
propagating at distance of 110 km are 70.31, 74.03, 74.46, 73.12, and72.12dBre1µPa
for source angle of ray -5 o ,-2.5 o , 0 o , +2.5 o , and+5 o .
Keywords: Underwater acoustic wave; reflection coefficient; full matrix, cascade
matrix system; n-layer; propagation; sediment;
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