Sound quality evaluation in passenger cars based on a two-dimensional booming and rumbling sound index

In automotive engineering, the production sound quality is a very important design requirement. Especially, the brand sound is an important strategic advantage for a car company. For the design of brand sound, the selection of a descriptive word for a car sound is one of major emphases in automotive sound quality research. Among many descriptive words for a car sound, recently both “powerfulness” and “refinement” have been widely used for the design of brand sound. In this paper, instead of such general words about production sound quality, a subjective evaluation for booming and rumbling sounds, which are professional words used by NVH engineers in automotive technology, is adopted. In a car’s developmental stage in most car companies, trained NVH engineers evaluate the booming and rumbling sounds subjectively. Sound indices, which are objective evaluations for booming and rumbling sounds, are developed in the paper. These indices are used for the objective evaluation of sound quality for 16 passenger cars, which are samples of well-known cars in the world. The results of objective evaluation are expressed in the two-dimensional sound indices. One is boom sound and the other is rumbling sound. The brand sounds of well-known cars in the world are very well represented in two-dimensional indices. In this paper, a production car is modified by using these two-dimensional indices and its sound quality is improved. In the future, the two-dimensional sound indices will be very useful for the development of a brand sound.