Passive sonar

There are two basic forms of sonar, active and passive. Passive sonar depends on the sound produced by the object observed and a simple, direct listening can be employed, though there are usually a transducer (to convert the acoustic... 

Dipping sonar devices equip manned antisubmarine helicopters and fixed-wing aircraft the aircraft flies low and suspends a sonar device at the end of a wire-link which is held just below the surface of the w. The sonar technique is also used in sonabuoys, which use active or passive sonar to detect and locate submarines. Sonabuoys provide anti-submarine warfare data to aircraft which cannot dip sonar devices while hovering overhead, the data being transmitted by coded radio signals... 

See Eel 639cm 533mm 1370kg 35/23 13/28km — Wire guided, active/ Passive Sonar Homing A/S S/M or FPBs... 

A 184 — 600cm 533mm - - - - Wire Guided Active/Passive Sonar A/S or A/Surface Ship or S/M... 

Mark 37 Mod 2 409cm 484.5mm 766kg 24 150kg HE Wire Guidance A ctive/Passive Sonar Homing A/S S/M... 

Victory, 1993] Victory, C. (1993). Comparison of signal processing methods for passive sonar data. Master s thesis, Department of Electrical Engineering and Computer Science, Naval Post Graduate School. 

The figure of merit (FOM), a basic performance measure involving parameters of the sonar system, ocean, and target, is computed for active and passive sonar systems (in decibel) as follows ... 

FIGURE 17.43 Generic passive sonar system. (Source Adapted from Knight, W., Pridham, R.G., and Kay, S.M. 1981. DIgltdIsigjidIpTocessmgfoTsonar. Proceedings of the IEEE 69(ll) 1454. IEEE 1981.)... 

In passive sonar, at low SNR, the optimal filters where / is frequency in hertz, G noise power spectrum. 

Tracking surveillance technology is varied in design and form. It ranges from simple beepers to sophisticated intelligent transportation systems. For example, there is radar to monitor over the horizon bi-static sensors for passive retrieval of emissions (cellular phones) or active sonar-hke capacity tagging systems that use projectiles to attach transmitters to moving objects illumination telescopic and detection systems. 

Type 41 - 244cm 400mm 250kg - - - Passive Homing Sonar Limited A/Surface or A/S S/M ... 

Type 42 - 244cm + 400mm 270kg — — — Passive Homing Sonar A/S Ship S/M and... 

SONAR allows the imaging of the seafloor and obstacles on it. An example of a side-scan sonogram mosaic of a mudslide is shown in Figure 3.5 (Prior and Coleman, 1978,1981). The soimd waves are emitted by a source and reflected off the seafloor and travel back to a receiver. The sound waves are produced by either active or passive systems. Active systems send out sound pulses. Passive systems monitor sounds emitted by the objects they are tracking. Ship-borne SONARs are active systems that are very powerful and can image seafloors and objects up to several kilometers from the source. The frequencies used in these systems determine their depth capabilities. A summary of some of the available side-scan sonar systems that are commercially available is presented in Table 3.8. 

The performance of sonar systems can be assessed by the passive and active sonar equations. The major parameters in the sonar equation, measured in decibel, are as follows ... 

In general, all three formats are required for the operator to make an informed decision. The operator must sort the outputs from all of the displays before classifying them into targets. For example, in passive narrow-band sonar, classification is usually performed on the outputs from spectral/tonal contents of the targets. The operator uses the different tonal content and its harmonic relations of each target for classification. In addition to the acoustic data information and displays, nonacoustic data such as environmental, contact and navigation information, and radar/sateUite photographs are also available to the operator. 

PASSIVE TORPEDO HOMING. COMMUNICATIONS WITH SUBMARINES. LONG DISTANCE SONAR... 

Sonar systems eanbe elassed as either active or passive. In active sonar an ultrasonie or acoustic pulse is transmitted... 

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