Acoustic Simulation and Validation to Realize Sound Quality Refinement of a Motorcycle

Sound image is one of valuable features for enhancing the competiveness in heavy motorcycles' marketing. In previous phase I study, sound synthesis technique was used to establish sound quality refinement targets which defined the exhaust and intake noise contributions for acoustic tuning of a 400 cc motorcycle. The motorcycle was thus aimed to magnify the sound components of lower engine orders for enhancing its sound perception in phase II. This paper focuses on phase II study which is the realization of sound quality improvement. This study first conducted optimized countermeasure designs of the exhaust and intake systems by acoustic simulation along with a design optimization software tool. Following that, candidate design changes were delivered for further prototyping, design validation and hardware tuning. The validation test results of the countermeasures under wide open throttle run-up condition showed that the sub 150 Hz order content at the rider's ear position was dramatically increased, successfully adding a positive low frequency note to the sound perception. The later subjective assessment also confirmed the sound quality improvement under run-up condition. Moreover, idle sound quality was also improved with a stronger beat subjectively.