| 摘要 |
PROBLEM TO BE SOLVED: To provide a Helmholtz sound absorbing body capable of absorbing sound efficiently. SOLUTION: An outer shape of this sound absorbing body 1 is a shape of tubular column, and an annular hollow part 20 is provided between an external wall 4 and an internal wall 5. This sound absorbing body 1 is provided with an annular opening 30 passing through from a through-hole 10 into the hollow part 20. A vibration system of spring mass is constituted based on mass of air in the opening 30 and the spring property of air in the hollow part 20 in this sound absorbing body 1. When the sound having resonance frequency in the vibration system of the spring mass enters the through-hole 10, the air in the opening part 30 vibrates hard, acoustic energy is converted into heat energy due to friction between the air in the opening 30 and the internal wall 5, and the heat energy is consumed to absorb sound. Since the hollow part 20 and the opening 30 are annular and area of the internal wall 5 coming into contact with the air in the opening 30 is large in this sound absorbing body 1, the frequency of the friction of the air vibrating in the opening 30 is increased to absorb sound efficiently. COPYRIGHT: (C)2010,JPO&INPIT
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