The basic buoy hull is a cylindrical alumi- 
num tube (Alloy 6063-15) approximately 16 inches 
in diameter by 7 feet long with a one-half inch 
wall thickness. The pressure capability of the 
hull design allows for a 1000-foot submergence. 
A net positive buoyance of approximately 150 
pounds is obtained including all internal com- 
ponents. Calculations made for assumed con- 
ditions of buoy attitude, mooring line length, 
and wire diameters indicate reduced drag and, 
consequently, the least heeling angle is ob- 
tained with the buoy moored in a horizontal 
position. Minimum heeling angle is desired to 
obtain satisfactory operation of the wave- 
height sensor which in the existing design has 
a depth limitation of 80 feet. Provision is 
made for the attachment of buoyance adjustment 
tanks and fairings at nose and tail. 
The noise hydrophone mount is attached to 
the underside of the main hull with provisions 
for suspending the hydrophone at desired depths 
below the hull as required. The wave-height 
measuring transducer is mounted on top of the 
hull with provisions for buoying the transducer 
above the main hull if desired. 
A taut-wire mooring system is used which 
employs a concrete block anchor and anchor 
line attachment bridle at the buoy end. An 
explosive anchor release is incorporated in the 
anchor line at the buoy end which effects buoy 
release and return to the surface under control 
of the recovery system. 
Access to the buoy interior is gained 
through an "0" ring sealed end cap held in 
place by a flanged coupling. Electrical con- 
nections from the buoy interior to the hydro- 
phone and wave-height sensor are made by means 
of Marsh Marine bulkhead fittings in the end 
cap. 
The measurement circuitry, data recording 
system, and electrical power supply are con- 
tained as a modular assembly which can be re- 
moved from the buoy hull in one piece. This 
arrangement permits simplified bench testing 
and servicing procedures. The equipment com- 
ponents are mounted on coaxially aligned 
stacked circular decks and the complete assembly 
is held in place within the hull by means of 
integral guide rails. 
TIMING AND CONTROL SYSTEM 
An electrically wound spring-driven clock 
(Massey Dickenson) provides the basic measure- 
ment sampling interval and control of buoy 
operation by means of the programmer. The 
accuracy of the clock is +10 seconds per day. 
The programmer provides for the sequential 
application of voltages to the measuring systems 
22 
and the operation of the photo-data recording 
system through a series of motor-driven cam- 
operated switches. Adjustable contacts on the 
main clock trigger the programmer into a measure- 
ment cycle once each sampling interval. 
During a measurement cycle, power is first 
applied to a thermal delay relay by the clock 
which allows a 20-second warmup period for the 
noise-measuring amplifiers. In series and 
simultaneously with the end of the warmup period 
a 60-second solid-state delay relay is actuated. 
During the delay period, the acoustic integra- 
tions are performed. Closure of the 60-second 
solid-state delay relay at the end of its cycle 
actuates the programmer which performs all sub- 
sequent functions, including channel selection, 
comparison for each channel, sea-state sensing, 
and frame shift of the camera. At the end of 
the program, the system is returned to its 
initial standby state. 
The programmer also controls a predetermining 
counter. The counter reading is recorded on 
each film frame along with the acoustic noise 
and wave-height data. When the predetermined 
timing interval has been reacned, the counter 
contacts energize the acoustic command recovery 
system, thereby initiating the recovery cycle 
at the end of the buoy operational period. 
ACOUSTIC MEASUREMENT SYSTEM 
The acoustic measurement system consists 
essentially of the hydrophone and associated pre- 
amplifier, the bandpass filter and matching 
amplifiers, and the rectifier/integrator circuits 
All amplifier and integrator circuits are tran- 
sistorized with the exception of the input stage 
of the hydrophone preamplifier. 
The measurement technique involves amplifi- 
cation and selective filtering of the acoustic 
signal. The output of each filter is rectified 
and integrated to produce one minute averages of 
the sound pressure in four, 1/3 octave bands at 
50, 100, 200, and 400 eps. 
The hydrophone signal is first amplified 
and shaped by a passive filter with bandpass 
from 30 to 600 cps. This filter serves to 
eliminate frequencies outside the band of in- 
terest and reduce the possibility of amplifier 
overloading. The bandpass filter output is 
then applied to four, 1/3 octave band filters 
connected in parallel through impedance matching 
amplifiers. The output of each 1/3 octave 
filter is matched to identical rectifter/ 
integrator circuits through variable gain linear 
power amplifiers. The averaged spectrum level 
output of the integrator circuits is stored in 
low-loss tantalum capacitors (General Electric 
Type 29F1074). 
