Parametric model for low-frequency index of subjective car interior sound quality

Low-frequency character is one of the most important properties for car interior noise quality, subjective sensation of this kind of sound character is usually expressed in the context of powerful, booming, annoying, and/or even offensive as indicated in some literatures. This study is to establish an index for sound quality focused on subjective perception of car interior noise with low frequency contents. In order to obtain an appropriate verbal descriptor for this feature, questionnaire for verbal description through subjective listening and imaging of sounds are carried out. A verbal expression "Dichen" in Chinese was concluded from statistical analysis of subjective listening data. Jury tests for indicator "Dichen" was performed by using binaurally recorded car interior noise as stimuli; subjective results are analyzed and correlated with objective quantities. Mathematical model for "Dichen" is developed as a function of 1/3 octave sound pressure levels, sharpness and roughness quantities. The proposed model was verified by data collected from subjective assessment with paired comparison and semantic differential methods. Results indicate a strong correlation between model predicted and subjective data, and therefore proved the developed model an effective index for subjective low-frequency perception.