Appendix A 



PRELIMINARY SPECIFICATIONS POR A SURFACR-TOTJED SUBBOTTOM 



PROFILING SYSTEM SUITABLE FOR MARINE CONSTRUCTION 



ENGINEERING APPLICATION 



For marine civil engineering applications, it is desirable to have 

 a high-resolution subbottom profiling system vet also capable of trans- 

 mitting sufficient power so that subbottom penetration is achieved in 

 water depths to at least 6,000 feet. A frenuencv of approximately 3.5 

 kHz may suit resolution needs as energy at this frequency will resolve 

 reflecting layers about 0.5 m apart. Minimum penetration desired is 

 200 to 300 feet in unconsolidated sediment in 6,000 feet of water. 



With the above admittedly general and somewhat arbitrary guidelines 

 in mind, some preliminary specifications of this desired subbottom 

 profiling system can be considered. 



The continuous reflection profiling system shall be an operationally 

 complete svstem composed of the following: 



1. transducer in a V-fin or other towed configuration 



2. high power transceiver in splash-proof and shock-proof 

 case for portable operation 



3. precision recorder in splash-proof and shock-proof case 

 for portable operation 



4. connecting cables 



5. instruction manuals 



A transducer utilizing a resonant frenuencv of 3.5 kHz shall be fur- 

 nished. Acoustic signal output of the unit shall be a short pulse of 1 to 

 2 cycles (at 3.5 kHz) duration. Rise time and ring time shall be small 

 (<100|jsec) . The acoustic source level shall be sufficient to provide 200 

 to 300 feet of penetration in a muddy bottom in 6,000 feet of water. The 

 transmitted beam width shall be 30 degrees or less. The transducer ele- 

 ment shall be tested to a maximum working depth of 500 feet of water. 

 Maximum weight of the transducer and V-fin shall not exceed 500 pounds. 



The transmitter section of the transceiver shall provide power output 

 sufficient for the above bottom penetration (200 to 300 feet, muddy bottom, 

 6,000 feet of water) at a frequency of 3.5 kHz. Pulse widths shall be 

 variable and selectable by a panel with selections for 5, 10, and 20 milli- 

 sec. A solid state transmit/receive switch shall be used. Output short 

 circuit and overvoltage protective breakers shall be provided. 



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