Determination of acoustic emissions using panel contribution analysis and scale modeling

Panel contribution analysis is frequently used to determine sound emissions from machinery as well as component contributions. The method consists of two measurement steps: volume velocities are measured for each panel with the machinery operating and transfer functions are measured between panels and receiver locations with the machinery turned off. It is demonstrated that transfer functions may instead be measured on scale models which approximate the geometry. This combination of panel contribution analysis and scale modeling is utilized to determine acoustic emissions from three similar air handlers positioned throughout a bakery. Transfer functions were measured between the panels and three different customer locations using a 1/10th scale model. Transfer functions are corrected to account for air attenuation and predicted sound pressure levels compare well with measurement. The described approach may be used to determine the sound pressure levels in large interior spaces before they are constructed so long as volume velocities on the source can be measured a priori. In addition, strategies, such as barriers and sound absorption, to reduce the noise by modifications to the acoustic path may be assessed prior to installation of equipment.