mounted, and are recharged through use of 
gravity-actuated mercury switches. 
DATA RECORDING AND PROCESSING SYSTEMS 
Counters are always used for a visual check 
of the frequencies and for precise end-point 
measurements. 
Three FM discriminators driving two X-Y plot- 
ters have been used for immediate visual display 
of the data (Fig. 4 and 5). Four-track tape 
recordings are also made with a precise 25-ke 
reference frequency recorded on one track. 
(Voice data may also be recorded on the same 
track.) The tapes are recorded at 15 ips and 
played back at 60 ips into the NODAC analog-to- 
digital converter. The IBM 7090 computer can 
linearize the Vibrotron output and utilize the 
temperature data to compensate the sound- 
velocity data for path-length changes due to 
temperature. The data may be printed digitally 
with time information, or digital X-Y plots may 
be made. 
APPLICATIONS OF THE SVTP INSTRUMENT 
Two of the uses to which the SVTIP instrument 
has been put by NOTS are given below. 
In fathometry, sound-velocity measurements 
to the bottom have yielded information for cor- 
recting a precision fathometer that assumes a 
sound speed of 4,800 fps. 
A study of the time variation in the distri- 
bution of sound velocity with depth at fixed 
stations has been made in the Outer Santa Barbara 
Channel. X-Y plots were made every 2 hours for 
36 hours down to the bottom of the basin, 
1,180 meters. Sound profiles obtained showed 
considerable activity in the water above the 
sill depth of 970 meters (Fig. 6). ‘The observa- 
tions obtained suggest a tidal influence with a 
semi-diurnal periodicity. Previous observations 
in the Southern California waters indicate a 
high degree of variability due to internal waves. 
Present measurements made with the SVTP instru- 
ment are too widely spaced to detect the shorter 
periods of such internal waves. More rapid 
sampling is planned in future studies. 
BIBLIOGRAPHY 
a. Greenspan, Martin, and Carroll E. Tschiegg. 
"Sing-Around Ultrasonic Velocimeter for 
Liquids ," REV SCI INSTRUMENT, Vol. 28, 
No. 11 (Nov. 1957), pp. 891-901. 
b. Tschiegg, C. E., and E. E. Hays. "Transis- 
torized Velocimeter for Measuring the Speed 
of Sound in the Sea," ACOUS SOC AM, J, 
Vol. 31, No. 7 (July 1959) pp. 1038-1639. 
172 
c. 
U. S. Naval Ordnance Test Station. An 
Instrument for Continuous Deep-Sea Measure- 
ment of Velocity of Sound, Temperature, and 
Pressure, by J. R. Lovett and S. H. Sessions. 
China Lake, California, NOTS, 9 May 1961. 
(NAVWEPS Report 7650, NOTS TP 2673.) 
