Target setting for enhancing sound quality of a motorcycle by sound systhesis technique

Sound quality is an essential competitive attribute for motorcycles' marketing. To tailor a particular brand statement and favorable sound characteristics, sound target setting and sound design are essential. A successful sound design is based on an appropriate and achievable sound target. This paper focuses on the method in setting sound target through benchmark, source contribution and sound synthesis technique. The analyses and tests were based on a motorcycle, powered by a 400 cc single-cylinder engine, which was proposed to enhance its sound perception as “sporty”. To obtain that desirable sound characteristic, this study conducted benchmark, subjective appraisal and objective analysis on loudness, sharpness and order spectra. The results showed that the motorcycle studied should amplify its sound level, especially magnify the lower integer-order components to realize that desired sound image. By measuring acoustic transfer functions and using matrix inversion method, the authors performed a noise source contribution analysis which validated the exhaust and intake systems should be improved first to fulfill a favorable sound quality. Through source contribution tuning, sound simulation concluded that increasing 6 to 10 dB both at the 1st and 2nd orders of intake noise and exhaust noise was the most practical solution for the “sporty” sound image of the motorcycle studied. As a result, this study successfully synthesized a promising sound target and the later jury evaluation validated that the proposed sound target fully accomplished the manufacturer's requirement. In this scheme, the proposed sound synthesis model along with an objective characterization of the key noise sources can provide sound tailoring functions and is applicable for other vehicle models.