1998 Fiscal Year Final Research Report Summary
Study on investigation of sound propagation on snow field and study on improvement method of sound information addressing
| Project/Area Number |
09450216
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Architectural environment/equipment
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| Research Institution | Niigata University |
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Principal Investigator |
IWASE Teruo Niigata University, Faculty of Engineering, Professor, 工学部, 教授 (30114391)
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| Co-Investigator(Kenkyū-buntansha) |
DOI Mareyasu Niigata University, Faculty of Engineering Lecture, 工学部, 講師 (60134954)
SAKUMA Tetsuya University of Tokyo, Graduate school of Engineering Lecture, 工学系研究科, 講師 (80282995)
YOSHIHISA Kouichi Meiji University, Faculty of Science and Technology, Associate Professor, 理工学部, 助教授 (60158491)
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| Project Period (FY) |
1997 – 1998
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| Keywords | Snowfield / Sound Propagation constant / Scale model experiment / Transfer function / Sound absorption coefficient / Ultrasonic sound / Auralization |
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| Research Abstract |
Field measurements and scale model experiments were carried out to investigate the sound propagation characteristics over snowfield and to obtain the improved sound addressing method over snowfields. Field measurement of sound propagation over snowfield with natura1 surface condition and compressed condition were carried out at Niigata prefecture in both winters of 1999 and 1999. Acoustical properties of snow, such as acoustic impedance of the surface, absorption coefficient, sound propagation constant in snow media also was measured. It was found that sound attenuation with sound propagating was very strong at low and middle audible frequency. Such a frequency area is very important, where spectra of speech almost are included. On the other hand, sound propagation in high frequency was smoothly performed. In case of height of sound source was high about 4m or 6m, attenuation at low and middle frequency propagation weakened and sound propagation characteristics would be improved. This tendency was clearly reconfirmed by the scaled model experiments using ultrasonic frequency sound source and microphone. It was also found that sound attenuation in snow media was stronger as frequency of sound was higher. As for propagation speed was low at low frequency and it closed to the sound speed in the air in higher frequency. Such characteristics were same as those of typical porous absorptive materials such as glass wool and rock wool. Double layered towel and jute close was match as the snowfield in 1/50 scale model experiment.
Transfer functions analyzed by FFT on sound propagation over snowfield with various condition and those in the snow media were applied to auralization of the sound field concerning with snow.
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