Prediction of sound reduction index of double sandwich panel

This study deals with the prediction model for SRI of double sandwich panels widely used in living quarters of ships and offshore installations. The proposed prediction model is obtained from the modification of the conventional models based on empirical measurements. The prediction model is divided into six frequency bands and the boundary of each band is determined from the physically meaningful frequencies including the mass-air-mass frequency, the limiting frequency, the critical frequency and their combination. The key factors including the critical frequency of a single sandwich panel, the sound absorption coefficient of the air cavity and the damping loss factor required to the prediction model and obtained from the empirical measurements and the physical features. Feasibility of the proposed model was verified from acoustical measurements using the double sandwich panels with varying of the width of the air cavity, the thickness and density of absorption material and the thickness of steel. Comparison with the conventional models shows that the proposed model produces more accurate prediction than the conventional models for the double sandwich panels.