4-12.
Sonar transmission losses can be
caused by
1.
low-frequency pinging signals
2.
low transducer power output
3.
high foreign matter content of
water
4.
weak pinging signals
4-13.
Assume that the crew on a destroyer
which was conducting passive sonar
operations, witnessed a surface
mine explosion at a distance of
several hundred yards.
If the
sonar equipment detected the sound
4 seconds after the explosion,
approximately how many seconds were
required for the sound traveling
through the air to reach the crew?
1.
1 sec
2.
8 sec
3.
16 sec
4.
4 sec
4-14.
What is the effect on a sound wave
traveling in the ocean when the
wave strikes the sea surface?
1.
Downward reflection
2.
Downward refraction
3.
Upward reflection
4.
Upward refraction
4-15.
At what angle must a sound beam
strike the side of a submarine to
produce an echo?
1.
180°
2. 90°
3. 45°
4. 0°
4-16.
Of the following surfaces, which
one will cause the LEAST amount of
reflections?
1.
Calm sea
2.
Rough and rocky bottom
3.
Sandy bottom
4.
Soft and muddy bottom
4-17.
Most individual sound reflections
are sharp and clear, but vary in
intensity.
Why does reverberation
appear as a continuous sound?
1.
The sound waves are reflected
at different intensities from
various objects
2.
The individual reflections
intermingle, and set up sound
waves of different speeds
3.
The individual reflections
occur at different distances
from the sonar, and arrive at
different times
4.
The sound waves are reflected
at different frequencies from
various objects
4-18.
Which of the following conditions
will cause the greatest amount of
reverberation in deep water?
1.
A smooth ocean surface
2.
A sudden change in water
density
3.
Choppy waves on the surface
4.
A sandy ocean bottom
4-19.
The factor that will most likely
determine maximum sonar range when
sound propagation conditions are
ideal is
1.
absorption
2.
refraction
3.
reverberation
4.
divergence
4-20.
Varying temperature differences in
the ocean have which of the
following effects on a sound beam
traveling therein?
1.
Bends and distorts only
2.
Splits and distorts only
3.
Bends and splits only
4.
Splits, bends, and distorts
4-21.
The bending of a sound beam when it
passes from a medium of given
temperature to a medium of
different temperature is known as
1.
refraction
2.
deflection
3.
reflection
4.
diffraction
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