The sound insulation performance of double-layer wall reduces because of a mass-air-mass resonant problem. To solve this problem, applying vibration absorbers in double-layer wall is a solution to improve the sound insulation performance at resonant frequency band. In theory, we simply modeled a double-layer wall as a MKC system and estimated the sound insulation performance by equations of motion. Then a parameter study on the effect of vibration absorbers was conducted. In experiments, the sound insulation performance of a double-layer wall is measured by sound intensity method in 1/5 scale model. The vibration absorber is made of materials as paper and urethane form and its natural frequency is made the same as the resonant frequency of double-layer wall. We made various arrangements of materials in double-layer wall to study the mechanism of vibration absorbers.
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