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Basic Study on Improvement of Interior Sound for Ultra-compact EV by Masking Including 1/f Fluctuation*

Ultra-compact electric vehicles (EVs) have advanced characteristics, such as compactness, light body, and low environmental impact. However, interior noise caused by the road and wind is a serious problem. We propose an active noise control (ANC) system for ultra-compact EVs using a giant magnetostrictive actuator. The proposed ANC system has a two-way interior noise control and achieves both noise reduction and masking, depending on the driver. In this study, we investigated the improvement of interior sound by masking considering 1/f fluctuation, which relaxs drivers by providing ride comfort based on their preference. In addition, we proposed a calculation method for 1/f fluctuation, including masking music by a numerical analysis using a Fourier transform. Furthermore, we conducted a real-time analysis of the music including 1/f fluctuation using the short-time Fourier transform and evaluated the relationship between the 1/f fluctuation of the whole music analysis and the appearance rate of 1/f fluctuation.