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Prairie-Masker is a radiated noise reduction system fitted to some US Navy warships, including the ''Spruance'', ''Oliver H. Perry'', ''Arleigh Burke'' class destroyers, and the ''Ticonderoga'' class cruisers of the US Navy. The system was also installed during the 1960s on a limited number of post WWII Guppy III modified, and later diesel submarines. The Masker and Prairie systems are designed to prevent the classification or identification of a warship's acoustic signature by another vessel, i.e. by a hostile submarine. Instead of hearing machinery, the ship sounds similar to rain on passive sonar. The Masker portion of the system is installed onto the hull of a vessel, usually near its machinery spaces. The Prairie portion of the system is designed to silence the vessels propellers. Originally classified, these systems are now used by several countries as part of their anti-submarine warfare solutions. ==Background== Ship silencing is an important part of reducing unwanted noise, which can severely limit a naval vessel's active and passive undersea warfare capability and increase the range or probability of detection by an unfriendly vessel. The US Navy maintains a Ship Silencing Program to address these problems. The goals of the Ship Silencing Program are a reduction of sonar self noise over the frequency range of passive capable sonar and the reduction in the ship's radiated noise to reduce detection by enemy submarines. Self-noise is the noise generated by a ship that has an effect on its own sonar and sensors. 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.〔''Information Sheet, Ship’s Silencing Program, Information Sheet Number: 9.7,'' US Navy Surface Officer Warfare School, p.1〕 The use of air-bubble and their effects upon acoustic wave propagation began to be studied systematically during the Second World War as part of a general effort to understand sound in submarine warfare. In the United States, this research effort was directed by the National Defense Research Committee (NDRC) and was carried out by various US Navy laboratories. The advances made in this research were published in ''The Physics of Sound in the Sea'' in 1946. Results of that study most pertinent to this discussion are found in Part IV of that volume ''Acoustic Properties of Wakes''.〔 ''Acoustic wave propagation in air-bubble curtains in water - Part I: History and theory,'' S. N. Domenico; Geophysics, Vol 47, No.3 (March 1982): p.345-353 〕 The use of air-bubble curtains have found wide spread applicability in reducing noise or the damaging effect of shock waves in a variety of industry from: underwater blasting, to pile driving, to explosive metal forming.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Prairie-Masker」の詳細全文を読む スポンサード リンク
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