Interior noise is basically airborne or structure-borne.
The excitation sources of vibratation and noise from engines can be divided as mechanical, combustion, and flow sources.
Tests using rolling roads (dynamometers) in semi-anechoic chambers to simulate engine noise in the absence of wind noise and road noise.
Frequency analysis in the form of third ocatves, spectral densities, Campbell''s diagrams, order tracks, etc. which divides up the response into frequency ranges and identifies resonances and excitation effects.
Modal analysis which identifies the behaviour of a system at an individual natural frequency.
Transfer path analysis which divides up the contributions to the interior noise into the individual structure-borne paths.