Sound signature design is gaining more importance within global auto manufacturers. ‘Sportiness’ is one of the important point to consider while designing a sound character of a car for passionate drivers and those who love aggressive driving. Nowadays automobile manufacturers are more focused in developing a typical sound signature for their cars as a ‘unique design strategy’ to attract a niche segment of the market and to define their brand image. Exhaust system is one of the major aggregate determining the sound character of ICE vehicles which in turn has the direct influence on the customer perception of the vehicle and the Brand image and also the human comfort both inside and outside the cabin.
This research work focuses on novel approaches to identify frequency range and order content by a detailed study of subjective feelings based on psycho-acoustics. Sound samples of various benchmark sporty vehicles have been studied and analyzed based on sound quality parameters. Subjective evaluations were carried out by NVH experts to understand the sporty character. Frequency ranges and order noise content were confirmed by correlation between subjective and objective evaluations under various customer drive patterns. It was discovered how the dominating exhaust firing sequence and its harmonics relate to sporty sound quality. Additionally, the quantitative order zones of the sporty sound quality was taken into consideration together with the curve distribution zones of the associated order noise. CAE analysis using commercial 1D software is done to simulate few concepts of exhaust system to get results in line with the above derived targeted zone.
This paper also focuses on the innovative methodology ideated to cascade the exhaust NVH performance from vehicle level to component level in the Universal Exhaust Source Simulator (UESS). This novel test rig and test methodology of insertion loss measurement is developed for component level validation of exhausts. This simulator (UESS) can also produce combustion order contents as that of the vehicle. Thus it acts as a complete replica of the engine itself, hence it reduces vehicle level iterations.
Finally, best configurations are tested on targeted vehicle to validate its sportiness by objective and subjective assessment. Results obtained shows very good correlation and proved that the defined order noise target zone of the sporty sound quality is accurate and very effective to get desired sporty character.