100 Lecture 5 
field tests were performed by the Chesapeake Bay Institute of Johns Hopkins 
University (Martin Pollack), by the U.S. Navy Underwater Sound Laboratory 
(Harry Sussman), and by the Woods Hole Oceanographic Institution (Earl Hays). 
REFERENCES 
1. M. Greenspan and C,E. Tschiegg, "Effect of Dissolved Air on the Speed on Sound in Water,” J. Acoust. 
Soc. Am., Vol. 28, 501 (1956). 
2.M. Greenspan, C.E. Tschiegg, and F.R. Breckenridge, "Temperature Coefficient of the Speed of Sound 
in Water Near the Turning Point,” J. Acoust. Soc. Am., Vol. 28, 500 (1956). 
3. F.H. Shepard, Jr., U.S. Patent No. 2,333,688 (November 9, 1943). 
4, W.E. Kock, U.S. Patent No. 2,400,309 (May 14, 1946), 
5. M. J. Larsen, U.S. Patent No. 2,580,560 (January 1, 1952). 
6, R.L. Hanson, "Applications of the Acoustic Sing-Around Circuit,” J. Acoust. Soc. Am., Vol. 21, 60-61 
(1949), 
7. E.W. Barrett and V.E. Suomi, "Preliminary Report on Temperature Measurement by Sonic Means,” J. 
Meterol,, Vol. 6, 273-276 (1949). 
8. G. W. Ficken, Jr., and E.A. Hiedemann, "Simple Form of the Sing-Around Method for the Determination 
of Sound Velocities,” J. Acoust. Soc. Am., Vol. 28, 921-923 (1956). 
9. M. Greensapn and C.E. Tschiegg, "Sing-Around Ultrasonic Velocimeter for Liquids,” Rev. Sci. Inst., 
Vol. 28, 897-901 (1957). 
10, M. Greenspan and C, E. Tschiegg, "Speed of Sound in Water by a Direct Method,” J. Research NBS, Vol. 
59, 249-254 (1957). 
11. E. Hiedemann, FIAT Rev. Ger. Sci., 1939-1946, Part I, 178 (1947). 
12. Huntgren and Hallman, "The Theory and Application of the Radar Beacon,” Proc. Inst. Radio Engrs., Vol. 
35, 716-730 (1947). 
13. R.D. Holbrook, "A Pulse Method for Measuring Small Changes in Ultrasonic Velocity in Solids with 
Temperature,” J. Acoust. Soc. Am., Vol. 20, 590 (1948). 
14, N. P. Cedrone and D, R. Curran, "Electronic Pulse Method for Measuring the Velocity of Sound in Liquids 
and Solids,” J. Acoust. Soc. Am., Vol. 26, 963-966 (1954). 
15. Tech. News Bull. NBS 39, 89 (1955). 
16, A. Lutsch, "An Apparatus for Measuring and Recording the Velocity of Sound and Temperature Versus 
Depth in Sea Water,” Acustica, Vol. 8, 387-391 (1958). 
DISCUSSION 
MR. J. CREASE enquired about the effect of dispersion on the velocity of 
sound in sea water between low and high frequencies and asked whether it was 
possible to make an estimate of the difference between Wilson's sound velocity 
data and the phase velocity at low frequencies. 
MR. GREENSPAN: In reply to Mr. Crease, I have already stated that the 
principle of operation of the velocimeter is suchthat the readings have a precise 
meaning only in liquids which are practically nondispersive. In sea water, the 
only dispersion for which there is positive evidence is that associated with dis- 
solved MgSO,. As Dr. Sette has pointed out, Fox and Marion* have measured the 
dispersion in MgSO, solutions by a differential method. Their data could best be 
fit by a single relaxation process centered at 150 kc, independent of concentra - 
tion. The total dispersion is about 13.6-1074 parts per mole per liter, and as the 
concentration of MgSO, in sea water is about 0.028 molar, the total dispersion 
in sea water should be about four parts in 10°, a value too small for Fox and 
Marion to detect reliably in sea water itself. 
If it should turn out that other and larger sources of dispersion exist, as- 
sociated, for example, with plankton or microbubbles, then new problems will 
arise. For one thing, most devices which operate at low frequency measure 
*F.E. Fox and T.M. Marion, J. Acoust. Soc. Am, 25, 661 (1953). 
