Other kinds of flow noise are the roar of the breaking bow and stern waves of a moving ship and turbulence produced by the sonar dome or towed array. A source of sonar self-noise is the pickup of electrical signals from machinery and electronic equipment. A frequent source of EMI is arcing of brushes and motors. Electronic equipment cabinets that have high voltage switching will cause EMI unless properly grounded. Typical shipboard noise problems include sound shorts, rattles, flow tones and unauthorized transmissions.
Self noise is affected by shipboard operations.
Self noise increases with ship speed, and will vary with the current engineering plant line-up and quiet ship operating condition in effect. Coating materials for the hull and masker air are the two methods used to acoustically isolate the hull from the water. Resilient Mounts - rubber shock devices used on machinery and piping. Distributed Isolation Material c. Flexible Connections - used on pipes and hoses.