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Silent running is a stealth mode of operation for naval submarines. The aim is to evade discovery by passive sonar by eliminating superfluous noise: nonessential systems are shut down, the crew is urged to rest and refrain from making any unnecessary sound, and speed is greatly reduced to minimize propeller noise.
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.
In electronics, motorboating is a type of low frequency parasitic oscillation (unwanted cyclic variation of the output voltage) that sometimes occurs in audio and radio equipment and often manifests itself as a sound similar to an idling motorboat engine, a "put-put-put", in audio output from speakers or earphones.
Radiated noise is the noise generated by a ship that has an effect on other ship's sensors, especially submarines. The Masker-Prairie countermeasure systems are key elements in this program to reduce radiated noise and self-noise that are not reduced by controlling the sounds at their source or their transmission to the hull. [2]
Instead of using a moving electromagnet (voice coil) placed within the field of a stationary permanent magnet to drive a cone, like a conventional subwoofer, on a rotary woofer, the voice coil's motion is used to change the angle of a fixed rotation speed set of fan blades in order to generate sound pressure waves.
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Editor's note: This story was originally published in 2019. We are republishing it as part of our winter coverage. Bitter-cold temperatures can make your home do strange things in the winter months.
The most common subwoofer driver sizes used for sound reinforcement in nightclubs, raves and pop/rock concerts are 10-, 12-, 15- and 18-inch models (25 cm, 30 cm, 38 cm, and 45 cm respectively). The largest available sound reinforcement subwoofers, 21-inch (53 cm) drivers, are less commonly seen. [citation needed]