By Gemma Simpson, 22 August 2007 11:02
Pictured is a typical Low Frequency Analysis and Recording gram - which is used to analysis the received sonar signals visually.
The fainter lines indicate when the shaft of the propeller turns on a vessel and the thicker lines indicate propeller blades turning.
By calculating the shaft and blade rate, the speed of a vessel can be calculated.
These rates can also be analysed aurally with "A" course students trained to recognise the acoustic signatures produced by a vessel.
Sound also allows operators to analyse other environmental factors which the visual signal may not pick up on - for example if the propeller is breaking the water's surface, which might indicate a vessel is empty.
Street added a good sonar operator must be patient, have meticulous attention to detail and be imaginative to get their head round what other, possibly enemy, submariners are thinking.
Photo credit: Crown Copyright
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1. Haydn Rees
'Top Gun' is for fighter pilots, in an environment where height and fire power is the key.
A Submarine Warfare school, where depth, stealth, and detection are the key would suggest 'Bottom Torpedo'?, or possibly 'Silent but deadly'.
On reflection, is may perhaps be an image that Her Britanic Majesty's Royal Navy is trying to shed, along with Rum and the Lash?