A Study on Sound Quality Evaluation Method for Vehicle Using Vital Information

The sound environment is an important factor determining the value of automobiles. Sound quality evaluation is important for enhancing the sound environment. We conducted an analysis with respect to two aspects: subjective evaluation and objective evaluation. In the subjective evaluation, we evaluated five types of engine sound with different timbres by using the semantic differential (SD) method. Three factors were obtained by factor analysis, namely, excitement, brightness, and responsiveness. The factor score of the excitement factor increases as the sound pressure of the order component of the stimulus sound increases. We conducted heart rate variability (HRV) analysis by using heart sounds as an objective evaluation index. The HRV analysis method using heart sounds has a problem that it is easily influenced by body movement noise. Therefore, we proposed an HRV analysis method that is robust to noise. From experiments using HRV analysis, we confirmed that as the order component of the stimulus sound increases, the rate of change of the low-frequency and high-frequency components also increases.