Velocity of Sound in Water
Sonar Equipment Sound Detection
The Side Looking Sonar
The side looking sonar detects sound returns and places them as
scan marks
to represent bottom detail. The depth below ship is the first return,
we shall
consider a flat bottom. Depth Below Ship, DBS, is the Sound Velocity
multiplied by First Return Time, FRT. At a side distance equal
to DBS,
the return time is 1.4 FRT.
SHIP
| \
| \
| \
| \
|
\
|
\
BOTTOM SIDE
Not to scale, but you use the right triangle formula where H is
the
distance from SHIP to SIDE and DBS is the length of the other two
sides
of the triangle.
HxH = DBSxDBS + DBSxDBS
So looking for a return 40% greater than the bottom return can
help
determine the amount of side looking ability you have.
While on sound velocity, which can vary in water, a good measure
in air
is 1000 feet per second. If you see TV interference on a stormy
day
listen for the thunder to occur later. A radio should crackle.
Back to water, a child invented an underwater sound communication
system by providing a small chamber and diaphragm for a mouth piece.
The water carries the sound to the next person.
Either Leno or Letterman had a demo on their TV show.
