70 



80 



O 90 



100 



110- 



120 



STRAIT of JUAN de FUCA 

 FALL PROFILE 

 25 m SOURCE 



J \ I L_L 



100 km 



150 km 



50 



200 



300 500 



FREQUENCY, Hz 



1000 



2000 



Figure 4.8. Propagation loss for optimum receiver depth vs frequency for ranges of 50, 100, and 

 150 km. Strait of Juan de Fuca fall profile ; source depth 25 m. 



The fall profile has a positive gradient to 30 m (see Figure 3.4), which includes the 

 source at 25 m. This contributes to the irregularities in the propagation loss curves (Figure 

 4.8) near 900 Hz. 



4.1.3 East of Singapore 



The sound speed profiles and sea floor sediment parameters for the East of Singa- 

 pore site are modeled for propagation loss computations in Tables 4.5 and 4.6. 



Winter 





Summer* 



Depth, 



Sound Speed, 



Depth, 





Sound Speed, 



m 



m/s 



m 





m/s 







1536.9 









1542.3 



10 



1537.4 



10 





1542.0 



50 



1538.7 



20 

 30 

 50 





1541.9 



1541.35 



1541.45 



*A non-positive gradient profile was chosen here because the autlior wanted to have 

 contrasting winter and summer conditions. 



Table 4.5. Sound speed in the water column, East of Singapore site. 



45 



