



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 



1 



0.0 



1523.79 



1617.79 



1.10 



0.06 



0.07 



1.5 



2 



78.0 



1830.0 



1943.0 



0.91 



0.07 



0.08 



1.95 



3 



191.0 



4200.0 





-0.1 



0.03 





2.37 



Table 4.6. Sediment parameters used in computations, East of Singapore. 



The sediment sound speeds are given for the winter profile and should be adjusted 

 for the summer case to keep the ratio of sound speeds (surface sediment/bottom water) to 

 0.99. The density of water was taken to be 1 .02 and the density in each sediment layer was 

 assumed to be constant. 



Propagation loss for optimum receiver depth as a function of frequency is shown in 

 Figure 4.9 (winter profile) and Figure 4.10 (summer profile). High bottom reflection losses 

 exist at this site due to the slow sound speed in the sediment. Therefore, the propagation 

 losses calculated for the summer profile are quite high and only visible on the graph at 

 50 km in the frequency range 800 to 4000 Hz and at 100 km for frequencies 2200-3200 Hz. 



Optimum frequency of propagation is near 3000 Hz for the summer conditions and 

 about 1000 Hz for winter conditions. The minimum loss is greater by more than 10 dB for 

 the summer profile. 



4.1.4 Lands End 



Computational models for the water column (Table 4.7) and for the sediments 

 (Table 4.8) for the Lands End site are the following: 



Winter 





Depth, 





Sound Speed, 



m 





m/s 









1491.1 



10 





1491.49 



20 





1491.51 



125 





1493.5 





Summer* 





Depth, 





Sound Speed, 



m 







m/s 











1515.6 



10 







1515.1 



20 







1515.0 



30 







1504.6 



50 







1494.3 



75 







1493.0 



125 







1493.8 



Table 4.7. Sound speed in the water column. Lands End site. 







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 



1 



0.0 



1670.0 



1710.0 



7.3 



0.50 



0.38 



1.85 



2 



5,0 



1710.0 



1757.0 



1.81 



0.38 



0.28 



1.85 



3 



30.0 



1800.0 



2090.0 



0.80 



0.03 



0.02 



2.0 



4 



320.0 



4360.0 





-0.01 



0.01 





2.64 



Table 4.8. Sediment parameters used in computations. Lands End. 



46 



