| 摘要 |
<p>The box functions according to the principle of a Helmholtz resonator, i.e. in part of the ventilation ducting, air works as a vibrating mass, and the air volume in the duct cavity acts as a spring. By partly filling the cavity with a porous absorption material, the frequency range over which absorption takes place is widened. The box has a longitudinal housing (1) formed by a top box (2) and a bottom box (3) which are connected by plate (4) at both ends. The top box has two angled partitions filled with sound absorbing material (15). The bottom box has two angled side walls (9,10), whilst the bottom (8) inside cavity (11) is also filled with sound absorbing material. The box may be fitted in a building facade above a window frame.</p> |
