Sound Quality Analysis of a Passenger Car Based on Rumbling Index

Rumbling sound is one of the most important sound qualities in a passenger car. In previous work, an objective evaluation method for rumbling sound was developed based on the principal component. In the present paper, the rumbling sound was found to effectively relate not only the loudness but also roughness. The last two subjective parameters are sound metrics in psychoacoustics. Principal rumble component, roughness and loudness were used as the sound metrics for the development of the rumbling index to evaluate the rumbling sound objectively. The relationship between rumbling index and these sound metrics is identified by an artificial neural network (ANN). Interior sounds of 14 passenger cars were measured, and 21 persons subjectively evaluated the rumbling sound qualities of these interior sounds. Throughout this research, it was found that the results of these evaluations and the output of a neural network have high correlation. The rumbling index has been successfully applied to the objective evaluation of the rumbling sound quality of mass-produced passenger cars.