STUDY ON THE CONTRIBUTION OF INTAKE NOISE USING COMPLEX TIME-TIME ANALYSIS AND SUBJECTIVE EVALUATION

Abstract

Recent research on time-frequency analysis using wavelet transforms has focused on analyzing wavelets using a mathematical approach. In this study, a measured signal is adopted as the wavelet, and we analyze the correlation between acoustic signals in the car cabin and air intake suction noise signals by applying the proposed system. Since the traditional calculation of correlation repeats the averaging procedure, the original signal must be stationary. Consequently, a technique for separating and identifying noise from each part of the engine is used for analyzing the noise source contribution. To apply the method to time-varying signals, we introduce the concept of an instantaneous correlation factor (ICF), and we prove that the dominant feature of the correlation can be estimated by the ICF. However, the ICF method has not previously used a time-varying analyzing wavelet. In this research, to conduct a practical analysis we proposed Time-Time analysis, which was developed based on the ICF. Furthermore, we also proposed Complex Time-Time analysis, extending into the complex region for improvement in accuracy. First, we verified the effectiveness of the ICF using simulated signals, and then we investigated the contribution of intake noise (which is one of the engine noises) to the car interior noise during acceleration. Using an ICF in which signals relating to each noise source are selected for the analyzing wavelet (AW), we showed that this technique is also useful for contribution analysis. We also conducted a fundamental experiment about audibility impressions.