When world-class motorcycle manufacturer Husqvarna (now part of the BMW Group) faced a noise, vibration, and harshness (NVH) problem, they approached LMS to help them analyze the sound performance of its motorcycles.
Husqvarna had two bikes they wished to test. Both were struggling to meet new noise regulations. The racing bike needed to pass the Federation Internationale de Motocyclisme (FIM), a static test whereby the bike is fixed on a stand in neutral gear and a microphone is placed 50 cm behind the exhaust nozzle.
“The difficulty is not passing the approval process; it is doing so while maintaining a high engine performance. Moreover, it is not satisfactory to solve these problems without first having fully understood the source of the critical noise phenomena,” said Alessandro Mantovani, Husqvarna mechanical engineer.< The bikes were installed in LMS’ semianechoic chamber equipped with a dynamometer to reproduce road conditions[/caption]
Husqvarna shipped both bikes to LMS’ main testing center in Belgium where they were subjected to an acoustic source quantification (ASQ) test. The ASQ is conducted in two steps: the operational measurements where the race or pass-by noise are replicated and measured; and the Frequency Response Function (FRF) measurements whereby a volume velocity source is placed on each bike to capture the microphone response to the calibrated noise from each source.
The bikes were installed in LMS’ semi-anechoic chamber equipped with a dynamometer to reproduce road conditions. More than 20 microphones were located around the individual motorbike elements which included the engine, gearbox, intake, exhaust, and rear tire. The LMS Test.Lab software combined operational and FRF data to determine the noise contributions of each possible source. From all the collected data, a ranking of the most “noise-generating” elements of each motorbike was established.
As a result of this procedure, LMS was able to precisely identify the main noise source for each test. “Husqvarna could not have confidently identified the noise sources by itself,” added Mantovani. “We had neither the instrumentation nor the know-how to do what LMS did. These results allow us to target the right components for noise emission for our future bikes, thereby reducing the amount of trial and error development that is so time and cost consuming.”
He and his engineering team implemented LMS Test.Lab software and the mobile LMS SCADAS Recorder hardware. “We use the system for benchmarking vibration and acoustic levels. Choosing a multi-purpose system helps us avoid an investment in several hardware and software systems. There may even be an opportunity to work with LMS on fluid dynamics optimization,” noted Mantovani.
Filed Under: Off highway • construction, Shocks + vibration control • gas springs, Software, Test + measurement • test equipment