'Before-and-after' results show the difference Source Path Contribution (SPC) makes by quickly finding the contributions, from specific components, to the Noise Vibration Harshness (NVH) experienced by the driver and the significance of the NVH path.
SPC determines the sources of the sound - or vibration - perceived by occupants of a vehicle and determines the routes they take. The results include a quantification of the source level, the sensitivity of the path and the contribution of each individual path to the receiver.
But it is only with the recent innovation of time-domain SPC that any type of event, including transient events, can be analysed.
“The best way to analyse the data is in an interactive manner, listening to the contributions, viewing the live spectrum and turning individual contributions or groups of contributions on and off,” says Brüel & Kjær Senior Application Engineer, Dave Bogema.
Consequently, pronounced differences between specific measurement locations on a diesel engine were able to show the origin and frequency components of high-frequency airborne sounds emanating from the turbocharger.
A diesel truck is a very good example to show where time-domain SPC is required, as its characteristic transient sounds make it very difficult to accurately assess, using only traditional frequency-domain analysis. In an example, on a diesel truck, several airborne and structure-borne paths from the engine were measured and analysed using time-domain SPC techniques.
By contrasting spectrograms that show the contributions from different directions, on different locations, with others that show the sensitivity functions of the transmission paths taken by each contribution, it is easy to identify problems.
About Brüel & Kjær
Brüel & Kjær (bksv.com) is a world-leading manufacturer and supplier of sound and vibration solutions for use in a wide range of applications including: environmental noise measurements, building acoustics, vibration measurements and quality control for use in the automotive, aerospace and consumer industries, as well as by local authorities.
We design and manufacturer sound level meters, microphones and accelerometers, conditioning amplifiers, calibrators, noise and vibration analysers and software.
Brüel & Kjær also runs a variety of training courses throughout the year, from basic introductions on noise and it’s effects to more specialised classes teaching customers how to get the most out of their equipment.
Free, online training courses - conducted by our expert engineers - run throughout the year too.