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SONARSubmitted by :-Parag Nikhra
E.C. IIIrd Year
(0915EC091059)
Submitted to :-
Mr. Lekhraj Sharma
Assistant Professor
(E.C. Dept.)IITM
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What is SONAR?
Stands for SOUND NAVIGATION ANDRANGING
Uses acoustical waves to sense thelocation of objects in the ocean
Uses transmitted and reflected underwatersound waves to detect and locatesubmerged objects or measure distancesunderwater
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Theroy :-
The simplest sonar devices send out a soundpulse from a transducer and then precisely
measure the time it takes for the sound pulsesto be reflected back to the transducer
The distance to an object can be calculatedusing this time difference and the speed of
sound in the water (approximately 1,500 metersper second)
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Relation B/W water depth &
system coverage :-
The range of the system coverage is a
function of water depth covering fromapproximately two to seven times thewater depth .
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Theory :- Equation 1-
d = s x (t/2)
Timeit takes half of the time to go
down and half to return
Speedapproximately 1500 m/s
through seawater
Distance
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Equation 2 -
SL - TL = NL - DI + DT
where SL is the source level, TL is thetransmission loss, NL is the noise level, DIis the directivity index of the array and DT
is the detection threshold.
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How SONAR works
Sends a burst of high frequency soundwaves
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Listens for an echo
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Horizontal Propagation :-
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Vertical Propagation :-
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Types of SONAR :-
Side-scan SONAR
Multi-Beam SONAR
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Side-Scan SONAR :-
One of the most accurate systems forimaging large areas of the ocean floor is
called side scan sonar. Side scan sonartransmits a specially shaped acousticbeam 90 degrees from the support craft'spath, and out to each side.
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Multi-Beam SONAR :-
excellent for mapping large areas of theseafloor rapidly with approximately 100%
bottom coverage Multibeam sonar also provide color images
with blue and green portraying deeper
areas and yellow and red portrayingshallower areas.
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Frequency :-
192 kHz (M-B SONAR) 50 kHz (S-S SONAR)
Shallower depthsNarrow cone angle
Better definition and
target separationLess noisesusceptibility
Deeper depthsWide cone angle
Less definition and
target separationMore noisesusceptibility
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Total system performance
There are four facts to a good sonar unit:
a) High power transmitter
b) Efficient transducerc) Sensitive receiverd) High resolution/contrast display
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Application :-
Overall survey to locate pipeline or cableroutes, seamounts, obstruction and other
features. Target search operations where small but
discrete objects are lost and requirepinpointing.
Mapping where large sections of seabed needto be imaged accurately.
Specifically, mine hunting, downed aircraftsearch and lost cargo search operations all
require the use of side scan.
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Uses
Submarine and mine detection
Depth detection
Commercial fishing
Diving safety
Communication at sea
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ANY QUERRY