The principal reason for making the Figure 4.14 and 4.15 calculations is that the 

 fine sand surface layer found at this site is not present in the sediments to the east 

 (150-200 km from the center of the site) but is still well within the Strait (References 10, 

 1 1). Therefore, acoustic propagation can vary greatly within the Korea Strait due to posi- 

 tion and frequencies of transmission even without a narrow frequency range. 



A second sample of sound speed profiles taken 34.5°-35.5°N, 130°-131°E, (East 

 Korea Strait) showed summer and winter profiles very similar to our sample and would 

 have like characteristic profiles. However, profiles from that part of the Strait (not 

 sampled) north of Tsushima Island may show different sound speed profiles due to the 

 influx of cold water from the Sea of Japan as well as possibly different sediment properties. 

 Acoustic propagation and optimum frequencies may differ in that part of the Strait as well. 



4.1.6 Straits of Sicily 



The numerical parameters for the models used in the calculations of propagation 

 loss for the site in the Straits of Sicily are given in Table 4. 1 1 (water column) and Table 

 4.12 (sediments for the shallow and deeper water models). As mentioned previously 

 (Section 3.6) we have taken the two geoacoustic models from Reference 13, that are 

 apphcable to sediments in water that is shoal of 200 m and to water depths greater than 

 500 m, respectively. The sound speed profiles representative of this site are given in 

 Table 3.11. The deeper profiles (to 500 m) are extensions of the sound speed profiles to 

 150-200 depths. 



Winter 



Depth of shallow model 



Water depth of deeper model 





Sound 





Sound 



Depth, 



Speed, 



Depth, 



Speed, 



m 



m/s 



m 



m/s 







1509.3 







1535.0 



50 



1509.7 



10 



1535.5 



100 



1509.5 



20 



1526.5 



► 165 



1512.1 



60 



1515.5 



500 



1517.0 



125 



1511.7 







150 



1511.8 







165 



1512.5 



lodel 



► 



500 



1516.8 



Summer 



Table 4.1 1 . Sound speed in the water column. Straits of Sicily. 







Sound 



Sound 











Bottom 



Sediment 



Speed 



Speed 



Gradient 



Absorption 



Absorption 





Layer 



Depth, 



Top, 



Bottom, 



Top 



Top, 



Bottom, 



Density, 



g/cm^ 



Number 



m 



m/s 



m/s 



s-1 



(dB/km)/Hz 



(dB/km)/Hz 



165 m Model: Surface sediment/bottom water =1.11 



1 



0.0 



1678.0 



1695.5 



8.62 



0.50 



0.45 



1.81 



2 



2.0 



1695.5 



1751.0 



3.53 



0.45 



0.31 



1.81 



3 



17.0 



2200.0 





-0.1 



0.02 





2.16 



500 m Model: Surface sediment/bottom water = 0.99 



1 



0.0 



2 



250.0 



3 



500.0 



1501.3 



1777.3 



1777.3 



1936.3 



2200.0 





0.86 



0.027 



.0345 



1.52 



0.56 



0.0345 



.0235 



1.83 



0.1 



0.02 





2.16 



Table 4.12. Sediment parameters used in computations. Straits of Sicily. 



52 



