Two-Stage Mounting System

A two-stage mounting system (raft mounting) is employed where there is a demand for high structure-borne noise attenuation. The main objective of a two-stage mounting system is to reduce vibration levels from machinery to foundation, and thereby to radiate noise levels from ship hull.

Design of raft mounting for ship-board machinery is an ongoing area of research. DRDO has developed and installed a two-stage mounting system for ship-board HP air compressor. A significant vibration reduction (25 dB) has been achieved, which in turn has reduced radiated noise levels.

The critical design aspects of the system are: optimum mass of raft (intermediate mass);selection /design of suitable mounts for both stages for desired vibration reduction; and minimum height of the system for ensuring stability.