Development of Psycho-Acoustic Indices for Vehicle Door Latch and Window Lift Systems

Abstract

In this thesis, perceived sound quality of electro-mechanical devices in vehicles is studied. Sounds of electro-mechanical devices in vehicles can be divided into simple impulsive sound and complex sound. Sound quality of simple impulsive sound is studied base on a case of door latch, and sound quality of complex sound is studied based on a case of window lift. First, an index that evaluates the sound quality of the door latches was developed and the modification of module was conducted to improve sound quality based on the results. To conduct the jury evaluation, various operating sounds of door latches were used. Through the results of the jury evaluations, it was found out that loudness and sharpness related metrics are dominant in the psycho-acoustic index we developed. In addition, this research investigates the main transfer path of operating sounds through sound field visualization and concludes what could reduce the impact sound of the door latch. Therefore, improvement of the door latchs sound quality could be verified by using the psycho-acoustic index. Next, I developed a psycho-acoustic index for assessing the sound of window lift modules during operation. Window lift operations were classified as ascent and descent, and sound quality indices were developed for each operation and compared. In order to quantify the subjective sound quality preferences, correlations between factors were determined through factor analysis. For ascent, the relevant factors were determined to be described by luxuriousness and uniformity. For descent, the relevant factors were explained by luxuriousness and strength. Correlations between each factor and previously developed sound quality metrics were also analyzed to finally derive an equation that explains the preference in terms of sound quality metrics.