著者

田中 大輔 石光 俊介

出版者

一般社団法人 日本機械学会

雑誌

Dynamics & Design Conference

巻号頁・発行日

vol.2016, 2016

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<p>Every year the City of Hiroshima holds the Peace Memorial Ceremony to console the souls of those who were lost due to the atomic bombing as well as pray for the realization of everlasting world peace. Since the ambient noise of this ceremony is very loud, these noise was tried to reduce using a passive method and Active Noise Control (ANC). There are some problems that audiences or TV crews cannot catch the meanings of presenter's messages such as the Prime Minister's, because of ambient noise. To reduce these noises, tents were prepared in the venue. There were also useful for protect people from the strong suns. The difference between the sounds near the loudest place in the park and those in the venue was measured to confirm the effectiveness of each countermeasure. The one of the loudest noise came from an opposite bank of the river. Though the noise was detected at the river side, it was not detected in the venue. As a result, the noise in the venue was reduced by 15 dB owing to each countermeasure. As most of the noise are speech, a 6-second young woman's voice was used as the noise source and reference signal in the ANC test of this study. Noise source includes the high frequency components up to 4000Hz. High-speed signal processing was required to reduce the noise that has high frequency components and changes its amplitudes rapidly. FPGA with a clock of 40MHz was selected for the fast signal processing. Filtered-x LMS algorithm was used in the ANC, and sampling frequency was 15 kHz and adaptive filter coefficients were set to 3000 tap. As the results of control, the noise was reduced by 10dB in 500Hz to 5000Hz.</p>