Panel contribution analysis for the interior region of a complex structure using the Helmholtz equation least squares method.

Abstract

The paper presents an experimental study on using Helmholtz equation least squares based nearfield acoustic holography to perform panel contribution analysis inside a complex structure with overall dimensions of 21 × 14 × 14 in.3 in the shape of an automobile passenger compartment. A point random force was used to excite this structure. The radiated acoustic pressures were measured by a linear array of 13 microphones scanning over the interior surface at close distances, resulting in 520 measurement points. These measured acoustic pressures were used to reconstruct the vibro-acoustic responses, including the normal surface velocity (NSV) and surface acoustic pressures (SAPs) of the cabin. Next, the reconstructed NSV and SAP are used to determine the normal-component of the time-averaged acoustic intensity on the surface, which was then correlated to the sound pressure level at any field point, say, at the driver ear position inside the cavity. The relative contributions from individual panels toward a specific field point are calculated by summing the acoustic power flow from individual panels, and their ranking is determined. The major advantage of this approach is that panel contributions toward any number of field points can be determined based on a single set of measurements.