Including Underwater Sounds Analysis
SONAR is an acronym for SOund NAvigation and Ranging - a classic example of this acoustic application in air is the flying bat,
SONAR versus RADAR
SONAR is the underwater equivalent of radar, and like radar its functions are many and varied. These include the detection,
There are basically two sonar modes of operation, 'Passive' (receiving or listening) and 'Active' (transmitting and receiving).
Radar operates on the principle of transmitting and/or receiving electromagnetic waves, traveling at approximately the speed of light
SONAR on the other hand, relies on sound or acoustic energy in water traveling at approximately 1,500m/sec, depending upon
Why Sound Energy?
In the dull, dense and conductive environment of seawater, electromagnetic waves and light rays are severely attenuated. Acoustic
The operational frequency of a specific sonar system is chosen to accommodate the required mode of application; this is critical
For example low frequency (say 1 kHz) systems may be used for long range 'listening' and detection, whereas higher frequency
The accepted formula for calculating wavelength (l) is -
The Acoustic Systems Trainer (AST) for SONAR
The study of sonar principles and techniques are equally as demanding as the study of radar principles and techniques.
With the appropriate scaling of the system operational parameters, such as an increase in frequency of operation
The system is comprised of a control Console, containing the CW and Pulse gating electronics, and the hardware/software-processing
The transparent Acoustic Tank is constructed from acrylic material, measuring 1.2 meters in length, 600mm deep,
A variety of active targets are mounted on a reversible, variable speed Target Transport System, which enables the Doppler
The passive targets consist of a set of scale model, brass propellers, with 2, 3, 4, and 5 blades, mounted on a variable speed
Acoustic damping material can be added to the tank for ‘mill pond’ quiet experiments to be conducted with the sensitive hydrophone,
Both narrow beamwidth and wide beamwidth high frequency transducers can be used; allowing beam interaction to be clearly shown on the P.C. based virtual instruments.
NPL Transducer Polar Diagram
Beam steering circuitry controls the phase drive to the transducers.
Digital Oscilloscope display.
Active and passive targets are studied, and the SSA - Spectrum Analyzer, displays the signatures of a selection of passive targets.
Digital Spectrum Analyzer
Sonar Techniques and Principles
The foundation of the sonar principle is based upon the physics of sound waves, and all of the influences affecting
Due to the wide range of variable electronic parameters, such as PRF, Pulse Width, Tx Frequency and
A university MSc degree dissertation has already been written using the early AST(Mk III) as a development platform at the University of Plymouth.
Some of the techniques and principles which can be demonstrated (and developed further) with the Acoustic Systems Trainer, include –
The largest installation of seven Acoustic Systems Trainers provides for fourteen students working in pairs.
The AST has a comprehensive Laboratory Manual, Instructor Guide, and User Guide, data acquisition software, and a complete set of accessories, including-