of sea water has been partly licked. You will note that -- because 

 it is available -- the instrument has rapidly created additional 

 sound-velocity programs. There is still room for improvement. 



For instance: There is need for a rugged, streamlined, 

 sound-velocity meter with a standardized scale which is the same 

 for all instruments and which can be handled very much like a 

 modern bathythermograph (BT) by quartermasters and sonarmen 

 aboard ships which are nriaking speeds of about 10 knots. The 

 absolute "accuracy" of such an instrument is no more critical 

 for velocity than the absolute accuracy of temperature in the pre- 

 sent BT. But the precision with which the instrument can record 

 a slope, that is, the velocity gradient with depth, is very import- 

 ant. If such an instrunnent were available as a replacement for 

 the BT (and good for greater depths) at anything like a reasonable 

 and comparable cost, I am sure it would get most serious con- 

 sideration. In addition to this simplified, rugged, sound-velocity 

 meter, the survey-type instruments are needed. 



I would like to add one more point on acoustics. Navy lab- 

 oratories. Woods Hole Oceanographic Institution, Scripps 

 Institution of Oceanography, and others, have been studying the 

 effects on sound velocity of pressure at great depths. Several 

 measurennents of the coefficient of sound velocity with pressure 

 were made off Guam from the bathyscaphe, Trieste. These 

 have been reported by Mackenzie^' . But a lot more needs to be 

 done. The proposed single-packaged means of obtaining direct 

 sound-velocity measurements at the exact spot while water 

 samples are collected will be helpful in several respects: The 

 tables of sound velocity with depth can be corrected, and the 

 computations for long echo sounding and other deep-water 

 sonic paths can be corrected to usable values. 



In addition, the horizontal changes in sound velocity, as 

 well as the vertical changes are important. I leave to your own 

 ingenuity the questions of proper readouts and the data processing 

 of such information. 



3/ Mackenzie, Kenneth V. 1961. "Bottom Reverberations for 

 530- and 1030-c.p. s. Sound in Deep Water." Journal of the 

 American Acoustical Society, vol. 31, no. 11, November, p. 1498. 

 (ED.) 



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