Effectiveness of structureborne noise isolation systems on a lightweight ship foundation

Radiated structureborne noise from main propulsion machinery in a lightweight, high‐performance craft is of concern. This is due to the conflicting requirements of human habitability and ship weight. Efficient structureborne noise isolation of the main machinery will reduce the weight of the acoustical treatment required in receiver spaces. Main machinery isolation involves the consideration of the mechanical vibratory interactions between the machine, subbase, and foundation as well as the elastic mountings that connect these components. This paper presents a method that allows an analyst to calculate the structureborne noise power transmitted into a structure composed of idealized finite length beams. Impedance relationships are developed for the machine, subbase, foundation, ship hull, and the intervening isolators. Idealized finite length beam impedances are derived for various boundary conditions. The results of a parametric study to assess the effectiveness of vibration isolators, for various system...