4-33.
Which of the following statements
regarding surface ducts is NOT
valid?
1.
Surface ducts may occur if the
temperature within the mixed
layer increases with depth
2.
Surface ducts may occur if the
temperature within the mixed
layer decreases with depth
3.
Surface ducts may occur if the
temperature within the mixed
layer remains isothermal
4.
Generally, the deeper the mixed
layer the more useful the
surface duct
4-34.
Which,
if any, of the following
statements pertaining to direct
path propagation is valid?
1.
Direct path is the simplest
propagation path
2.
Direct path ranges occur where
there is slight to moderate
reflection in the layer
3.
The source and receiver must be
within 90° of one another in
order for direct path to be
useful
4.
None of the above
4-35.
What influence does half-channel
conditions have on the speed of
sound in water?
1.
Sound speeds increase to the
top of the main thermocline,
then decrease
2.
Sound speeds decrease to the
top of the main thermocline,
then increase
3.
Sound speed decreases with
increasing depth
4.
Sound speed increases with
increasing depth
4-36.
Where is the deep sound channel
axis depth located?
1.
At the depth of maximum sound
speed in the deep sound channel
2.
Always above the mixed layer
depth
3.
At the depth of minimum sound
speed in the deep sound channel
4.
Always within the main
thermocline
4-37.
What is another name for the deep
sound channel?
1.
The Optimum (OP) channel
2.
The Sound Fixing and Ranging
(SOFAR) channel
3.
The Range/Bearing (RAB) channel
4.
The Search and Rescue (SAR)
channel
4-38.
4-39.
4-40.
4-41.
4-42.
4-43.
The relative strength of a shallow
sound channel depends upon which of
the following characteristics?
1.
Surface turbidity
2.
Surface turbidity and
temperature
3.
Stratum thickness
4.
Density
Heavy shading on the Shallow Sound
Channel Cutoff Frequency display
indicates what limiting frequency
range?
1.
1 to
50 Hz
2.
51 to 150 Hz
3.
151 to 300 Hz
4.
300 to 500 Hz
Which of the following noise
sources is NOT referred to as
ambient noise?
1.
Noise due to earthquake
activity
2.
Noise due to precipitation
3.
Self-noise
4.
Fish/crustacean noise
What is the primary source of low
frequency ambient noise?
1.
Distant shipping traffic
2.
Fish
3. Ocean fronts
4.
Turbidity currents
At what sea height would waves
first begin to affect active
sonobuoy detection?
1.
12 ft
2.
9 ft
3.
6 ft
4.
3 ft
What is a good rule of thumb for
sea state noises?
1.
Sea state noise increases
approximately 2 dB for each
increase in sea state
2.
Sea state noise increases
approximately 3 dB for each
increase in sea state
3.
Sea state noise increases
approximately 5 dB for each
increase in sea state
4.
Sea state noise increases
approximately 6 dB for each
increase in sea state
27
