enough of the necessary scatterers present to 
operate the instrument satisfactorily in ocean 
water. Although the device described was de- 
signed to operate over a range of 1 mm/sec to 
10 m/sec, it is reasonable to assume that, with 
minor modifications, it would operate over a 
much wider range. This instrument should pro- 
vide a reliable index of turbulence in ocean 
currents because of its excellent response to 
rapidly changing flowse 
NOMENCLATURE 
c = speed of sound, m/sec 
f,f* = transmitting frequency, cps 
f' = transmitting frequency, mc 
= Doppler frequency, cps 
8 f = difference frequency, cps 
= returned frequency, cps 
P/P, = relative pressure, dimensionless 
v. = velocity of flow along the axis of the 
transducer-pair, m/sec 
6 = an angle, deg. 
y © normalized sensitivity, cps/mc/m/sec 
REFERENC 2S 
1. J. W. Johnson and R. L. Wiegel, "Investiga- 
tion of Current Measurement in Estuarine 
and Coastal Water", September 1958, Cali- 
fornia State Water Pollution Control Board 
Publication #19, Sacramento, California. 
2. G. A. Klotzbaugh, "Theory of Continuous- 
Tone Reverberation", J. ACOUST. SOC. AM. 
275 Noe 5, September 1955. 
199 
