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Question 1

Expand the Acronym SONAR

Answer 1

Sound Navigation and Range

Question 2

Explain the purpose of a hydrophone in a passive SONAR system

Answer 2

Converts sound in the water to electrical energy

Question 3

List the Categories into which sonar are grouped?

Answer 3

Passive, Active, Navigational,Communications, Torpedo Decoy, Surveillance, Intercept

Question 4

What are the major components of a passive sonar system?

Answer 4

Hydrophones, Pre-Amplifier, Front end conditioner, Beamforming network, signal, display processer, audio processer.

Question 5

Why is beamforming carried out?

Answer 5

to achieve directivity and gain

Question 6

A measure of a sonars ability to beamform to increase the signal to noise ratio is known as what?

Answer 6

Directivity Index

Question 7

What is fast fourier Transformation?

Answer 7

Mathematical means by which a computer can calculate the frequency components of a waveform arriving at the array

Question 8

What are ways of increasing sonar processing gain?

Answer 8

Narrowband processing, integration, normalisation/equalisation, beam forming.

Question 9

The distance between one element in an array and the last element in the array, or the size of the array itself determines what?

Answer 9

Array cut frequency

Question 10

Explain the purpose of a transducer in an active SONAR system?

Answer 10

To convert electrical energy into sound energy and vice versa

Question 11

Expand the acronym CW and state its primary use?

Answer 11

Continuous wave - primarily used for doplar tracking

Question 12

List the 3 active transmission TYPES?

Answer 12

Ripple, sectoral, omnidirectional

Question 13

Define the term “pulse length”

Answer 13

the length of the transmission

Question 14

What information can be gained from an active SONAR intercept

Answer 14

Frequency, pulse length, mode and classification

Question 15

List the 4 ways to increase SONAR gain?

Answer 15

Narrowband processing, Beamforming, intergration, Equalisation/normalisation

Question 16

What are the 3 transmission MODES?

Answer 16

CW, FM, AM

Question 17

List 3 ‘Towed Array’ preformance factors

Answer 17

Array cant, array kite, parralax error, sound velocity, array droop.

Question 18

What is the purpose of the front end conditioner?

Answer 18

Converts analogue data recieved from the hydrophones into digital data.

Question 19

What is the purpose of the pre-amplifier?

Answer 19

Boots the received signal prior to signal processing taking place.

Question 20

What does the process of ‘gain’ achieve?

Answer 20

Increase the processing gain of the SONAR in a particular direction.

Question 21

What does the ‘Array cut frequency’ determine?

Answer 21

Frequency response of the array.

Question 22

What is the advantage of ‘sectoral’ transmissions?

Answer 22

Concentrating all of the available power into one sector enabling maximum gain

Question 23

What does the term source level refer to in active SONAR?

Answer 23

Amount of power measured a metre from the source, Power is dB

Question 24

List 3 displays on which the passive SONAR can be displayed/

Answer 24

Bearing time display, Frequency time display, Polar, Frequency Azimith display, Towed Array.

Question 25

What types of displays are the main surveillance, detection and tracking displays available to us?

Answer 25

Bearing time, frequency azimith, frequency time, towed array.

Question 26

List the generic towed array components from FWD to AFT

Answer 26

Leader, Towed cable, FWD Vim, Fwd IM, Acoustic Arpeture, AFT IM, AFT VIM,

Question 27

Why does towed array ambiguity exsist?

Answer 27

Because the TA’s only significant dimension is length.

Question 28

List 2 propogation paths that contribute to multipath interference?

Answer 28

Direct, Bottom bounce.