SOUND INSULATION DEVICE FOR SOUNDPROOF WALL

PROBLEM TO BE SOLVED: To provide a low-cost sound insulation device offering high sound insulation efficiency.SOLUTION: A sound insulation device A4 includes front and rear vertical wall plates 11, 12 that are fitted at a crown of a soundproof wall B and parallel to each other, an intermediate plate 14 between the front and rear wall plates, and a bottom plate 13 for closing an undersurface of the front, rear and intermediate plates. Since a sound insulation effect declines due to a resonance phenomenon in a space S surrounded by the front, rear and bottom plates, a reinforcing frame 17' and a side plate 15' having openings 17a, 15a are installed in a lengthwise direction of the space, for suppressing reflection of an incident sound. Reflection is suppressed also by providing a sound absorber 18 on an inner surface of the side plate 15' and others. The resonance phenomenon is suppressed by laying out a partition plate 17 that replaces the reinforcing frame 17' such that a distance between the partition plates and the side plates is not an integral multiple of half a wavelength of a frequency number when a sound reduction effect between the partition plates and the side plates declined. The configuration efficiently improves decline in the sound reduction effect due to the resonance phenomenon, and enables effective sound reduction. The reflection may also be suppressed by providing the sound absorber 18 on both side surfaces of the partition plate 17.SELECTED DRAWING: Figure 7 【課題】安価な防音効率の高い防音装置を得る。【解決手段】防音壁Ｂの頂部に取付けられ、上下方向の並列する前後壁板１１、１２と、その前後壁板間の中間板１４及びその各板下面を塞ぐ底板１３とを有する防音装置Ａ４である。その前後壁板と底板で囲まれた空間Ｓ内では共鳴現象により減音効果が低下するため、補強枠１７'及び側板１５'を開口１７ａ、１５ａを有するものとして、前記空間の長さ方向に対し、入射音による反射を抑制する。また、側板１５'等の内面にも吸音材１８を設けることにより反射を抑制する。補強枠１７'に代えた仕切板１７は、各仕切板間及び側板間が減音効果が低下した周波数の半波長の整数倍とならないように配置することで、前記共鳴現象を抑制する。このような構成により、共鳴現象による減音効果の低下を効率よく改善し、効果的な減音ができる。前記仕切板１７の両側面にも吸音材１８を設けて反射を抑制し得る。【選択図】図７