In a previously reported analysis of abnormal sounds quantified in terms of acoustic pressure level, there were problems such as insufficient information on high-frequency sounds. In the present study, quality characteristics of in-car devices were considered in a wider sense and a new analysis was performed, in which vibration acceleration of in-car devices was used to evaluate operational functions. In the post-assembly inspection of in-car devices for abnormal sounds, inspectors have been evaluating operational sounds qualitatively by subjective human criteria. As these criteria vary from one inspector to another,in some cases defective products are misjudged as normal and are shipped to customers. In the evaluation of operational functions of in-car devices in this study, operational sounds were replaced with a numerical vibration acceleration value and multivariate continuous data were analyzed by the RT method. By establishing fixed inspection criteria, we are hoping to achieve more accurate product discrimination and to automate the inspection process.
