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Noise and vibration control. Noise generated on board ships and submarines can have far-reaching effects on the ability of the vessel to operate safely and efficiently. Military vessels in particular need to be quiet to avoid detection by sonar, so many methods have been used to limit a vessel's noise signature.
The hissing of high voltage transmission lines is due to corona discharge, not magnetism. The phenomenon is also called audible magnetic noise, [1] electromagnetic acoustic noise, lamination vibration [2] or electromagnetically induced acoustic noise, [3] or more rarely, electrical noise, [4] or "coil noise", depending on the application.
A long-range acoustic device ( LRAD ), acoustic hailing device (AHD) or sound cannon is a specialized loudspeaker that produces sound at high power for communicating at a distance. It has been used as a method of crowd control, which has caused permanent hearing damage, having an extremely high decibel capacity (up to 160 dB measured at one ...
Active noise control ( ANC ), also known as noise cancellation ( NC ), or active noise reduction ( ANR ), is a method for reducing unwanted sound by the addition of a second sound specifically designed to cancel the first. The concept was first developed in the late 1930s; later developmental work that began in the 1950s eventually resulted in ...
The first working full-scale MHD ship. A magnetohydrodynamic drive or MHD accelerator is a method for propelling vehicles using only electric and magnetic fields with no moving parts, accelerating an electrically conductive propellant ( liquid or gas) with magnetohydrodynamics. The fluid is directed to the rear and as a reaction, the vehicle ...
Underwater acoustics (also known as hydroacoustics) is the study of the propagation of sound in water and the interaction of the mechanical waves that constitute sound with the water, its contents and its boundaries. The water may be in the ocean, a lake, a river or a tank. Typical frequencies associated with underwater acoustics are between 10 ...
Example of airborne and structure-borne transmission of sound, where Lp is sound pressure level, A is attenuation, P is acoustical pressure, S is the area of the wall [m²], and τ is the transmission coefficient. Acoustic transmission is the transmission of sounds through and between materials, including air, wall, and musical instruments.
The 29th Motor Torpedo Boat Flotilla was a motor torpedo boat (MTB) flotilla crewed by Royal Canadian Navy (RCN) reservists in service with the Coastal Forces of the Royal Navy during the Second World War. The 29th MTB Flotilla had a short and distinguished history in the English Channel, including action during the Normandy landings in 1944. [1]