MEASUREMENT TECHNIQUE TO ASSESS THE ACOUSTIC PROPERTIES OF A SILENCER COMPONENT FOR TRANSIENT ENGINE CONDITIONS

This paper describes the development and validation of procedures for measuring the acoustic properties of an individual component of an exhaust system on a test bed under engine acceleration representing realistic operating conditions. However, collection of such data requires reliable induct pressure measurements where the contamination of the acoustic pressure field by shear layer turbulence and other hydrodynamic disturbances [1] make this a formidable challenge. The technique was first developed and optimized on a cold flow bench to simulate partly the acoustic conditions during engine acceleration, before applying it to an actual vehicle. Bench test results showed that order analysis measurement techniques can be employed to evaluate the acoustic performance of a silencer component for variable harmonic excitation in the presence of mean flow. The additional factors concerned in performing measurements on the test bed are illustrated by some preliminary measurements.