E-10 

 Acoustic Profiles 



Three simultaneous acoustic profiles were obtained 

 (Fig. E5) . One was made by the ship using the hull-mounted 

 transducer. It sonifies a strip of seafloor as wide as 

 about 40% of the water depth. The second was made by the 

 pinger above the depressor. At a depressor elevation of 

 20 meters, this second sound source sonifies a strip of 

 seafloor about 40 meters wide. The third profile was made 

 directly from the sled. The pinger here has its transducer 

 mounted some 10 cm above the base of the skis so that when 

 the sled is in contact with the bottom a very narrow track 

 is being explored. A sub-bottom profile is generated from 

 the sled pinger with a penetration that ranges from 1 to 2 

 meters down to 20 meters in well-stratified soft material. 



The three profiles permit geological features to be 

 observed over a wide range of sizes and wavelengths. Fur- 

 thermore, since the depressor is 100 meters ahead of the 

 sled, the operator has an early warning of features to be 

 encountered by the sled, giving her/him time for reaction 

 and planning to maximize sled contact with minimum risk of 

 hang-up or equipment damage. The double ping (>30° sled tilt) 

 capability allows the surface vessel to reverse course or 

 stop altogether, often before significant additional tension 

 is observed on the tow cable. 



Field of View 



At typical tow speeds of 0.8 to 1.2 knots the camera 



