Development of sound-quality indexes in a car cabin owing to the acoustic characteristics of absorption materials

This study presents a method to predict the quality of sound in a car cabin when the acoustic characteristics of absorption materials in a car are changed. We proposed a signal processing model based on an acoustic ray tracing method to predict the variation of interior car cabin sounds corresponding to changes in the acoustic absorption material attached to the sidewall of the engine room of a virtual car. The interior sounds corresponding to seven different acoustic materials were simulated using this model and were recorded inside of a virtual car. The predicted interior sound was compared with the recorded interior sound. The recorded interior sounds were used to develop a sound quality index estimating the variation of sound quality owing to the change in acoustic materials. The sound quality index was developed in terms of sound metrics correlated with subjective evaluation of the recorded interior sounds. The sound metrics were investigated based on psychoacoustic parameters and the acoustic properties of the absorption materials. Finally, the proposed method was validated with real car by experiments. The proposed method can be used for the prediction of the variation of sound quality of interior sound owing to changes in the acoustic materials at the early car-design stage and thus aid in the selection of the optimal acoustic material in view of car weight reduction.