| Project/Area Number |
60550035
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
応用物理学一般(含航海学)
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| Research Institution | Faculty of Science, Ehime University |
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Principal Investigator |
HASEGAWA Takahi Faculty of Science, Ehime University , Associate Professor, 理学部, 助教授 (10029879)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUZAWA Kiichiro Faculty of Science, Ehime University, Professor, 理学部, 教授 (40036182)
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| Project Period (FY) |
1985 – 1986
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| Project Status |
Completed (Fiscal Year 1986)
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| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1986: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1985: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | Ultrasound / Sound intensity / Acoustic radiation pressure / Diffraction / Fresnel diffraction / Scattering / Nearfield / 円形振動子 |
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| Research Abstract |
A new method has been developed for the absolute measurement of ultrasonic intensity in the nearfield. Three theories have been presented for this purpose.
In the first place, a new solution for the velocity potential in the nearfield of a circular piston source has been developed. According to the new theory, the Rayleigh surface integral, giving the velocity potential for a circular piston source, reduces to an infinite series of spherical harmonics when the coordinates are suitably chosen. The theory has the advantages that it includes neither approximations nor numerical integrations.
Secondly, ultrasonic scattering by a sphere placed in the nearfield has been calculated by use of the above theory. So far sound scattering by a sphere in the nearfield had never been calculated analytically.
Finally, the acoustic radiation pressure has been calculated for an elastic sphere placed in the nearfield of any circular piston source.
Each theory has been compared with experiments. Excellant agreement has been observed between theory and experiment. The results compel the conclusion that we can determine the absolute value of acoustic intensity in the nearfield of circular piston source by measuring the acoustic radiation pressure on a sphere placed there.
It has been found that beryllium and fused silica are most suitable for the sphere material because of flatness in their frequency characteristics of radiation pressure.
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