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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