EFFECTS OF PERMEABILITY ON SOUND ABSORPTION AND SOUND INSULATION PERFORMANCE OF ACOUSTIC CEILING PANELS

In room acoustics, it's very important to adjust reverberation properly. From the point of view of room acoustic design, the ceilings are considered for the best part for adjusting reverberation of the room. The ceiling panels are often made of rock wool and have little permeability. Although they are commercially available and well marketed, full investigations regarding acoustic properties haven't been given yet. In this study, the effects of permeability on sound absorption and sound insulation characteristics of acoustic ceiling panels are investigated. A theoretical model is proposed and discussed by changing its related parameters in each case of introducing permeability and micro-perforating. From this investigation, it was found that the sound absorption characteristics are strongly affected by change in flow resistivity in the former case and perforation ratio in the latter case, and both cases show a similar tendency. The effects of porous materials installed between the ceiling panel and a rigid back wall are also considered. At the same time, it's concerned that sound insulation performance might be deteriorated by introducing the permeability of the ceiling panels. This issue is also investigated by using simulation models of a ceiling-floor system and discussions are given to the influence of permeability on sound insulation performance of impact sound of floor. The results show that radiated power caused by a point force excitation generally increases by introducing permeability. However, at some frequencies, sound insulation performance is improved due to mitigation of the effect of mass-air-mass resonance of the ceiling-floor system.