SONIC DEPTH FINDER 



Tlie sound apparatus was installed for the purpose of determining 

 the practicability of locating icebergs by means of submarine echoes. 

 The sound installation on the Tampa consisted of the following : 



(a) Two r2-spot MV hydrophone hnes, housed in type JC bhsters, the blisters 

 being installed symmetricallj', one on either side of the vessel, centered on frame 

 29, and separated horizontally by a distance of 14 feet. 



(5) Type CAG-4217 compensator, to bring the sound responses from the 

 several receivers into phase. Installed in chart room. 



(c) Test panel, consisting of 24 milliammeters, each in series with a microphone 

 of the receiving line to indicate condition of microphones. Installed in chart 

 room. 



{d) Two Submarine Signal Co. 540-cycle oscillators, mounted in fore and after 

 peak tanks, respectively. Forward oscillator mounted 2 inches abaft of frame 5, 

 on starboard bow, in skin type mounting, facing outboard and downward at an 

 angle of about 15° below the horizontal plane. After oscillator mounted on 10- 

 inch channel iron on port side of after peak tank, facing outboard and at an 

 average distance of about 18 inches from skin of ship. Base line from center of 

 microphone lines to forward oscillator, 47 feet; to after oscillator, 126 feet. 



(e) Five-kilowatt, Holtzer-Cabot motor generator, installed in engine room. 



(/) Cutler-Hammer starting box, installed in engine room, with remote control 

 in chart room. 



ig) Oscillator control panel, mounted in chart room. 



(/)) Type SE-1987 sonic depth finder, installed in chart room. 



Originally only one oscillator, the forward one, was contemplated. 

 Upon the completion of the forward oscillator calibration was 

 attempted, using it as the sound producer. It was found that 

 the base line was rather short and that the direct signal from the 

 oscillator was so loud as to destroy the biaural effect. Even in the 

 deepest water no satisfactory results were obtained. It was then 

 decided to install the oscillator in the after peak tank. This was a 

 much better location witli reference to the microphones, the direct 

 signals being completely absorbed by the hull of the ship and an 

 increase being made in the base line. The location was bad for 

 signals from ahead. The propeller sounds did not affect the trans- 

 mission or reception. 



Upon installation of the after oscillator the sonic depth finder 

 was tested and the compensator compensated. The vessel proceeded 

 down Boston Bay to Stellwagen B.ank, testing all apparatus in 

 shallow and deep water. A 75-foot patrol boat was used as a sound 

 maker and the compensation made. 



(45) 



