The interior noise & vibration in a vehicle compartment is caused by various contributing sources - primarily suspension and engine vibration. This raises two fundamental questions: “Which sources are causing the most interior noise?” and “Which paths are causing the most interior noise?”. Source Path Analysis attempts to answer these question by relating the vibrations measured at different locations around the vehicle to the sounds and vibrations measured inside the vehicle.

The first stage of Source Path Analysis is to compute the Principal Components of the system using Singular Value Decomposition (SVD). The SVD computation produces a transformation (eigenvector) matrix that is then used to derive cross spectra between the virtual (vibration) references and the measured (sound) responses. These Virtual Cross Spectra are used to calculate a set of Reference Related Auto (RRA) spectra for every response position, where each RRA spectrum is related to just the coherent contributions from a particular reference source input.

Full Noise Path Analysis requires not only data at the Source and Response locations, but also data at the attachment points of the vibration isolators (anti-vibration mountings). This data can either be from random excitation in the case of Road Noise or to cyclic excitation as in the case of Powertrain Noise. The software estimates the dynamic forces present at the isolators and determines the contribution from each location as perceived at the (driver) response positions. The various contributions from the paths are ranked according to their severity at different frequencies or speeds.