Sonar, (from “sound navigation ranging”), technique for detecting and determining the distance and direction of underwater objects by acoustic means. Sound waves emitted by or reflected from the object are detected by sonar apparatus and analyzed for the information they contain.

1. SONAR SYSTEM

2. INTRODUCTION
Sonar (SOUND NAVIGATION AND RANGING)
Sonar is a technique that uses sound propagation to navigate,
communicate with or detect objects on or under the surface of the
water, such as vessels, boats, ships and objects.

3. HISTORY OF SONAR:
Some animals (dolphins, bats, some shrews, and others) have used sound for
communication and object detection for millions of years, use by humans in the
water is initially recorded by Leonardo da Vinci in 1490: a tube inserted into the
water was said to be used to detect vessels by placing an ear to the tube

4. Working of sonar:

6. APPLICATIONS OF SONAR TECHNOLOGY
THE BASIC USE OF SONAR TECHNOLOGY IS TO ESTIMATE THE DEPTH,
RANGE, AND DIRECTION OF ARRIVAL OF OBJECTS. FOLLOWING ARE THE
VARIOUS DIFFERENT APPLICATIONS OF SONAR TECHNOLOGY:
- SPECIAL SONARS ARE USED IN SHIPS AND SUBMARINES FOR
UNDERWATER COMMUNICATIONS.
- MEDICAL IMAGING FOR THE DETECTION OF CYSTS AND CANCER
CELLS ARE DONE USING SONAR AND THIS METHOD IS KNOWN AS
SONOGRAM.
- IT IS USED FOR THE DETECTION OF ENEMY VESSELS AND TORPEDO
BY THE MILITARY.
- SONAR ALSO FINDS APPLICATION IN INSPECTING PIPELINES THAT
CARRY OIL AND GAS FOR DETECTING POSSIBLE DAMAGES.

7. TYPES OF SONAR:
There are two types of sonar:—
 Active sonar
 Passive sonar

8. Active Sonar

9. There are 3 modes of operation for active sonar:
1. MONOSTATIC MODE:

10. 2. BISTATIC MODE:

11. 3. MULTISTATIC MODE:

12. BLOCK DIAGRAM OF ACTIVE SONAR

13.  Active sonar uses sound transmitter and receiver .And there are 3
modes of operation :
1. Monostatic mode
2. Bistatic mode
3. Multistatic mode
 Monostatic mode : when the transmitter and receiver are at the
same place.
 Bistatic mode : when the transmitter and receiver are separated
by some distance.
 Multistate mode : When more transmitters (or more receivers)
are used, again spatially separated.

14.  Transmitter : The transmitter generates the outgoing pulse. It determines pulse
width, pulse reception frequency, modulation and carrier frequency.
 Transducer array : The individual transducers are simple elements with little or
no directionality. They are arranged in an array to improve the directivity index,
which improves the figure-of- merit by noise reduction.
 Beamforming processor: The input/output of each transducer is put through a
,Beamforming processor which applies time delays or phase shifts to each of the
signals in such a way as to create a narrow beam in a particular direction.
 Duplexer switch : it is a switch that toggles between transmitter and receiver.
 Synchronizer : Provides overall coordination and timing for the system. Reset the
display for each new pulse in order to make range measurements.
 Receiver : Collects the received energy. The receiver may also demodulate the
return if frequency modulation is used on transmission
 Display : Puts all of the detection information into a visual format. There are
several types:
1. A-scan : the signal along a single beam for a portion of the listening cycle. A
target appears as a raised section if it is in the beam.
2. PPI(plan position indicator) : A top-down (geographic view). The sonar
system must sequentially search individual beams which are displayed in their
true or relative form. The strength of the return is represented

15. Following are the features of Active Sonar system.
• It consists of transmitter and receiver both.
• Active sonar transmits sound waves towards the object and receives
reflected waves from it. Active Sonar sounds are emitted in pulse forms and it
listens for the echo after transmission.
• The reflected waves are used to detect the object and measure its distance.
• As active sonar transmits sound waves in the sea, it is considered to be
harmful for the marine life.
• Active sonar has capability to detect vessels which are quiet and are difficult
to be detected by passive sonar as explained below.
• Active sonar can detect marine mammals in shipping lanes or in high sound
pressure zones.

16. Passive Sonar

17. PASSIVE SONAR SYSTEMS.
The main difference between passive and
active sonar is that a passive sonar system do not
emit any signals.
In this the target itself is the source of the energy
which propagates to the receiver.

18. Block diagram of passive sonar:

19. HYDROPHONE ARRAY.
THESE ARE THE SENSITIVE ELEMENTS WHICH DETECT THE ACOUSTIC ENERGY EMITTED FROM THE TARGET. AGAIN,
THEY ARE ARRANGED INTO AN ARRAY TO IMPROVE THE BEAMWIDTH. COMMON CONFIGURATIONS ARE CYLINDRICAL
OR SPHERICAL. THE CYLINDRICAL ARRAY OPERATES AT A FIXED VERTICAL ANGLE, USUALLY DOWNWARD. THE
SPHERICAL ARRAY, WHICH IS COMMON ON SUBMARINES, HAS A MUCH WIDER VERTICAL FIELD-OF-VIEW. SINCE THE
SUBMARINE MAY BE BELOW WHAT IT IS TRACKING, THE ARRAY MUST BE ABLE TO LOOK UPWARDS TO SOME EXTENT.
THE LARGE DOWNWARD ANGLES ARE ONLY USED FOR BOTTOM BOUNCE DETECTION. USING A BEAMFORMING
PROCESSOR (DESCRIBED BELOW) THE FIELD-OF-VIEW IS BROKEN DOWN INTO INDIVIDUAL BEAMS IN THE VERTICAL
AND AZIMUTHAL DIRECTIONS.
BEAMFORMING PROCESSOR.
UNLIKE ACTIVE SYSTEMS WHICH TRANSMIT AND RECEIVE IN A SET DIRECTION, THE PASSIVE SYSTEM MUST LISTEN TO
ALL ANGLES AT ALL TIMES. THIS REQUIRES A VERY WIDE BEAMWIDTH. AT THE SAME TIME, A NARROW BEAMWIDTH
IS REQUIRED FOR LOCATING THE SOURCE AND REJECTING AMBIENT NOISE. THESE TWO OBJECTIVES ARE ACHIEVED
SIMULTANEOUSLY BY THE PASSIVE BEAMFORMING PROCESSOR. THE IDEA IS VERY SIMILAR TO THE ACTIVE SYSTEM.
THE PASSIVE BEAMFORMING PROCESSOR APPLIES A UNIQUE SET OF TIME DELAYS/PHASE SHIFTS TO THE SIGNAL TO
CREATE A PARTICULAR BEAM. THE DIFFERENCE IN A PASSIVE SYSTEM IS THAT THIS PROCESS IS REPEATED SEVERAL
TIMES, EACH WITH A DIFFERENT SET OF TIME DELAYS/PHASE SHIFTS, IN ORDER TO LISTEN TO MANY NARROW
BEAMS NEARLY SIMULTANEOUSLY. THE RESULT IS A SET OF BEAMS THAT COVER THE FIELD-OF-VIEW OF THE ARRAY.

20. BROADBAND DISPLAY.
THE OUTPUT OF THE BEAMFORMING PROCESSOR IS DISPLAYED AS A BEARING TIME HISTORY (BTH):THE NEWEST
INFORMATION IS AT THE TOP OF THE DISPLAY. THE BEAMWIDTH OF THE SYSTEM DETERMINES HOW ACCURATELY THE
BEARING CAN BE MEASURED BY SUCH A DISPLAY. A COMMON BEAMWIDTH IS ABOUT 5O. THE TOTAL AMOUNT OF
TIME DISPLAYED FROM TOP TO BOTTOM CAN BE CONTROLLED (TO SOME EXTENT). A QUICKLY UPDATING DISPLAY THAT
ONLY KEPT INFORMATION FOR A FEW MINUTES WOULD BE USEFUL FOR CLOSE CONTACTS WHOSE BEARINGS ARE
CHANGING RAPIDLY. ON THE OTHER HAND, A LONG TIE HISTORY IS MORE USEFUL FOR DETECTING LONG RANGE
CONTACTS, WHOSE BEARINGS ARE ONLY CHANGING SLOWLY.
NARROWBAND DISPLAY.
FOR A PARTICULAR BEAM, THE TIME HISTORY OF THE FREQUENCY IS CALLED A WATERFALL DISPLAY. THIS CAN BE USED
TO GAIN ADDITIONAL INFORMATION FROM A CONTACT WHICH IS ALREADY BEING TRACKED BY ANOTHER SYSTEM. IN
ORDER TO SEARCH FOR CONTACTS ON THE BASIS OF NARROWBAND INFORMATION ALONE REQUIRES A DIFFERENT TYPE
OF DISPLAY. ONE POSSIBILITY IS TO SIMULTANEOUSLY DISPLAY SEVERAL DIFFERENT BEAMS, EACH SHOWING A MINI-
WATERFALL DISPLAY, WHICH ARE CALLED GRAMS.
FREQUENCY ANALYZER.
THE FREQUENCY ANALYZER BREAKS THE SIGNAL INTO SEPARATE FREQUENCIES. THIS IS THE SPECTRUM OF THE SIGNAL.
FOR PROCESSING PURPOSES, THE FREQUENCIES ARE DIVIDED INTO SMALL BANDS KNOWN AS FREQUENCY BINS. THE
WIDTH OF EACH BIN IS CALLED THE ANALYSIS BANDWIDTH.

21. Although active sonar was used by surface craft in World War II,
submarines avoided the use of active sonar due to the potential for
revealing their presence and position to enemy forces.
However, the advent of modern signal-processing enabled the use of
passive sonar as a primary means for search and detection operations.
Passive sonar has several advantages :
• It is silent.
• If target radiated noise level is high, it can have a greater range than
active sonar.

22. Following are the features of Passive Sonar system.
• It consists of receiver part only.
• It does not transmit sound waves but receives sound waves emitted by
sea animals used for communication. It also receives other vibrations.
Basically passive sonar is used for detection of noise made by others
(engines, propellers, animals etc.).
• Passive Sonar keeps large sonic database. Moreover sonar operator
classifies signals by use of computer and uses stored databases in order to
identify classes of ships and take action accordingly.
• As it does not transmit waves, it is considered to be safe for sea animals
compare to active sonar type.

23. Presented By:
• Sanskruti solkar
• Khushi singh
• Pranali salvi
• Sakshi shelar
THANK YOU
Feel free to ask us about your doubts.