Sound absorbing panels principle
Sound absorbing panels material, such as centrifugal glass wool, rock wool, mineral wool, plant fiber spraying, sound absorption mechanism is a large number of tiny pores within the material, acoustic waves along the pores can be deep inside the material, and materials The occurrence of friction to the sound energy into heat. The sound absorption characteristics of the porous sound-absorbing material are increased with increasing frequency, which means that the low-frequency absorption is not high-frequency absorption. The necessary conditions for the sound absorption of porous materials are: the material has a large number of gaps, the gap between the interconnected, the pores into the material inside. One of the misconceptions is that the surface roughness of the material with sound absorption performance, it is not true, such as pull the cement, the surface of the concave and convex stone is basically no sound absorption capacity. The second is to understand the material is a large number of holes within the material, such as polystyrene, polyethylene, closed-cell polyurethane, etc., with good sound absorption performance, in fact, these materials because of the internal hole is not connected, Material internal vibration friction, so the sound absorption coefficient is very small.
With the wall or ceiling there is the air layer of the perforated plate, even if the material itself sound absorption is poor, this structure also has sound absorption performance, such as perforated gypsum board, wood, metal plate, and even slit sound absorption brick. This type of sound absorption is called Helmholtz resonance sound absorption, sound absorption principle is similar to the thermosacoustic acoustic resonance, the material external space and the internal cavity through a narrow bottleneck connection, sound wave incident, the resonant frequency, the neck The intense resonance between the air and the internal space consumes sound energy. Helmholtz resonance absorption is characterized by only a large absorption coefficient at the resonant frequency.
Film or sheet with the wall or the roof can also absorb sound when the cavity, such as wood, metal plate made of ceiling or wall panels, etc., the structure of the sound absorption mechanism is thin plate resonance sound absorption. At the resonant frequency, sound energy is absorbed due to the intense vibration of the thin plate. Most of the thin plate resonance absorption has good sound absorption performance at low frequency.