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Mechanism of Light Weight Sound Insulation Material Using Thin-film Cells

Article of Honda R&D Technical Review Vol.32 No.1

Summary

Weight reduction of the sound insulation material used to enhance cabin quietness is being advanced for the purpose of reducing vehicle weight. Sound insulation material with a structure of double walls with an intermediate layer of porous material between them is frequently used. There are reports from previous research that the use of thin-film cells instead of porous material can maintain similar sound insulation performance while enabling weight reduction. However, since the mechanism of sound insulation by thin-film cells is not clearly understood, in the present research, the question of why thin-film cells possess the same sound insulation performance as porous material was examined, with a focus on the propagation speed of sound waves transmitted through thin-film cells (apparent sound speed). The relationship between sound insulation performance and apparent sound speed was also formulated as an equation in order to obtain adequate sound insulation performance, and a method of deriving the apparent sound speed from the internal structure of the thin-film cells was devised. By means of the above examination of the mechanism, findings were obtained to enable performance design of lightweight sound insulation material using thin-film cells.

Reference

(1) Koyasu, M.: Shaon Kyuon Zairyo no Riron to Fukugo Zairyo, Journal of the Japan Society for Composite Materials, Vol. 2, No. 4, p. 145-152, (1976) (in Japanese)
(2) Sato, S., Yamaguchi, T., Tsuboi, Y., Kondo, T., Noguchi, Y., Kurihara, I.: Sound Transmission Loss of High Performance Double Walls Included Thin-Film Cells, The proceedings of The Computational Mechanics Conference, 259, (2018) (in Japanese)
(3) Misaji, K.: Biot Parameta no Onkyotokusei ni Taisuru Kandokaiseki, Nichias gijutsu jiho, Vol. 4, No. 375, p. 1-6, (2016) (in Japanese)
(4) Muto, D., Takano, Y.: Effect of Acoustic Characteristics of Gases on Transmission Loss of the Double-wall Structure, Transactions of the JSME, Vol. 74, No. 746, p. 2495-2503, (2008) (in Japanese)
(5) Kato, D.: Predictive model of sound propagation in porous materials -Extension of applicability in Kato model-, The Journal of the Acoustical Society of Japan, Vol. 64, No. 6, p. 339-347, (2008) (in Japanese)
(6) Yamaguchi, T.: Wave propagation in media having damping properties like porous media, The Journal of the Acoustical Society of Japan, Vol. 62, No. 1, p. 62-70, (2005) (in Japanese)
(7) Iwase, T.: Observation of sound propagation in glass wool by use discrete sound sources and consideration on the insertion effect of porous material into double leaf wall, Proceedings of the meeting, the Institute of Noise Control Engineering of Japan, p. 57-60, (2012) (in Japanese)
(8) Mizuno, S., Mu, R., Toyoda, M., Takahashi, D.: Measurement of the Directional Distribution of Incident Energy on the Wall Surface, AIJ Kinki Chapter research meeting, Vol. 51, p. 65-68, (2011) (in Japanese)
(9) Shimokobe, Y., Yamaguchi, T., Sato, S., Kondo, T., Noguchi, Y., Kurihara, I., Tsuboi, Y.: Sound Insulation Analysis for High Performance Double Walls Included Thin-Film Cells, Dynamics and Design Conference, 340, (2019) (in Japanese)

Author (organization or company)

Ikumi KURIHARA(Innovative Research Excellence)、Takashi KONDO(Innovative Research Excellence)、Takao YAMAGUCHI(Gunma University)

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