Target setting and source contribution for sound quality of a motorcycle

Sound quality is an essential competitive attribute for motorcycles’ marketing. In this study, the sound perception of a motorcycle, powered by a 400 cc single-cylinder engine, didn’t achieve its “sporty” statement and the associated sound quality refinement engineering was initiated. The first phase of refinement included benchmark, noise source contribution and target setting. This paper focuses on the methods in setting sound target through source contribution and sound synthesization. Noise data were measured in a hemi-anechoic chamber with a rolling road facility. Loudness, sharpness and order spectra were used to provide objective quantification metrics. From the results of subjective and objective evaluation, it was concluded that the motorcycle studied should increase its sound pressure level, loudness and sharpness; it also should magnify the lower integer-order components of the perceived sound and suppress the single-cylinder engine characteristic half-order components. The noise source contribution results validated the exhaust and intake systems should be improved first to fulfill a favorable sound quality. Combining the objective, subjective and source contribution results, this study successfully synthesized a promising and feasible vehicle level sound target. It was then cascaded to get the synthesized intake and exhaust noise targets for next CAE design modification.