Research vessels built to stringent underwater-radiated noise standards usually have diesel-electric propulsion drive systems. These research vessels can be deployed for fish stock assessment or for bottom mapping using sophisticated sonar systems. The electric motor is a low noise and vibration source that drives a specially designed, large, and slow-turning propeller. The power comes from two-stage isolation mounted diesel-generators or gensets. This combination of machinery can be treated along with the use of hull insulation and damping to such an extent that the acoustic energy reaching the wetted hull is minimized. This article covers how airborne noise flanking affects the vibration effectiveness of two-stage-isolation gensets on three vessels. Theoretical and antidotal results on quiet research vessels indicate that airborne noise flanking of machinery isolation systems adversely affects their underwater radiated signature. This is especially true for diesel-generator drive systems installed on two-stage isolation mounts. Airborne noise from the diesel impinging on the nearby hull and tank structure may become a significant factor of radiating underwater energy. This path and potential methods of minimizing its impact are discussed with respect to two-stage isolation systems. Airborne noise flanking is discussed for systems with open- and closed-bottom intermediate rafts and for a totally enclosed genset.
Airborne noise flanking of shipboard vibration isolation systems
Flankierender Luftschall bei Schiffsantrieben im Zusammenhang mit Schwingungsisolationssystemen
Sound and Vibration ; 40 , 12 ; 19-23
2006
5 Seiten, 18 Bilder, 1 Tabelle, 12 Quellen
Aufsatz (Zeitschrift)
Englisch
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