Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, measure distances (ranging), communicate with or detect objects on or under the surface of the water, such as other vessels.

1. Assignment on Sonar
*
Presented by: Patel Urvi M.
Reg. No.: FRRTM 0200444
FPTM Department,
College of Fisheries, Shirgaon,
Ratnagiri, Maharashtra.

2. *Sonar
 SONAR (an acronym for Sound Navigation and Ranging) is an
acoustic equipment that works with the principle of underwater
sound propagation like echosounder.
 Principle is similar to echo sounder. In case of echo sounder, the
ultrasonic sound waves are transmitted vertically downward, but in
SONAR, the sound beam can be directed to any angle by turning the
transducer to any bearing around the vessel to 360º.
 Originally it was called as “ASDIC” which stands for “Allied
Submarine Detection Investigation Committee” developed for the
naval welfare as a device to detect sub marine during the World War
I. In World War II, the Americans used the term SONAR for their
systems.
 Later, this is used for finding fishes and become indispensable
equipment for the successful and profitable fishing operation.

3. *Working
*In this system a electric pulse is generated and sent through a
transmitter which is converted into sound wave by the transducer and
sent into the water.
*sound waves are reflected by the underwater object and strikes the
transducer which converts it into an electrical signal which is then
amplified by receiver and sent to the display screen.
*The time taken by sound wave to come back is recorded.
* And by knowing the speed of sound wave in water the distance can
be easily calculated by formula.
*Distance = speed x time

5. *Working of Sonar

6. *Main components of SONAR
SONAR has the four basic components :
1. Transmitter
2. Transducer
3. Receiver
4. Display

7. *Transmitter
*Transmitter is in the case of sonar, the transmitter generates
pulses of electrical energy and pass on to the transducer.
*It excites the sensors with electrical signals. These signals are
converted in to sound energy and the waves are radiated under
water.
*The transmitted signals strike the target object and reflects
back.

8. *Transducer
*The transducer is the heart of a Sonar.
*It is the device that changes electrical pulses into sound
waves or acoustic energy and back again.
*In other words, it is the device that sends out the sound
waves and then receives the echos, so the sonar can interpret
or “read” what is below the surface of water.
*SONAR is able to train(rotate) the transducer through 360o
and also be able to tilt.

9. *Receiver
*The SONAR receiver is similar in operation to that of
echosounder. The very weak signals that are returned from
fish shoal or any target to the transducer are amplified to a
sufficient magnitude and then sent to the display unit.

10. *Display
*It displays the processed data in a visual format. The
display is either a scanned image or PPI (Planned
Position Indicator) image.

11. Types of
Sonar
Active Sonar
Monostatic
Mode
Bistatic
Mode
Multistatic
Mode
Passive Sonar

12. *Active sonar
*Active sonar uses sound transmitter and receiver .
*Active sonar creates a pulse of sound, often called a "ping", and then
listens for reflections (echo) of the pulse.
*There are 3 modes of operation :
1. Monostatic mode
2. Bistatic mode
3. Multistatic mode

13. *Continue…
*Monostatic mode : when the transmitter and receiver are at the same
place.
*Bistatic mode : when the transmitter and receiver are separated by
some distance.
*Multistatic mode : When more transmitters (or more receivers) are
used, again spatially separated.

14. *Passive sonar
*Passive sonar listens without transmitting.
*This is based on the detection of sounds produced by a moving
object or marine vessel.
*Aquatic animals, Ships, Submarines produce distinct sounds. These
sounds emanating from different Target Objects is used for detection
and estimation of target object.
*Passive Sonar cannot determine the range of the target object unless
it is used in conjunction with other devices.
*Passive detection is widely used in the study of marine life.

16. *Fishing with sonar
*The echosounder indicates the bottom of the sea and fish
under the vessel, the sonar can search a whole area,
horizontally, in all directions.
*Used for pelagic fishing methods such as purse seining and
mid water trawling. It is also quite useful for assessing
bottom conditions and configurations, which are of interest
for bottom trawling and other bottom fishing techniques

17. *Applications :
The SONAR Technique is used to determine the depth of the sea.
The SONAR technique is installed in every ship to locate
underwater hills, valleys, submarines, icebergs, and sunken ships
etc to avoid a disaster.
The SONAR system is also used in Military.
The fishermen have used SONAR technology to find fish.
The SONAR technology also used in the medical industry like
Sonography.
The SONAR technology is used in the navigation system.

18. *Advantages of SONAR
It is used to determine depth of water.
It is used for various water based activities. This is due to the fact
that sound waves used by SONAR do not attenuate much in the sea
water compare to radar waves and light waves.
The communication speed of the SONAR system is very high.
It is very accurate system.
It is not too expensive.

19. *Disadvantages of SONAR
The waves emitted by SONAR interfere with whales,
dolphines, seals, turtles, sea lions etc. Hence it threatens
marine life.
SONAR system generates lot of noise which depend on sound
levels generated by SONAR.
The acoustic waves used in SONAR are affected by sound
velocity variations over depth. This causes refraction of
acoustic energy. Moreover ocean acts as lossy medium for
acoustic waves. This requires use of high level sound waves to
compensate for the losses which results into threat for humans
( e.g. well divers and military) and sea animals.

20. *THANK YOU