US Patent 7677359 Sound absorbent

Sound absorbent (1) of a hard material, such as metal, glass, hard plastic or composites thereof, for absorption of acoustic waves by friction of viscous flow, essentially in the frequency range between 100 and 4000 Hz. The sound absorbent (1) comprises a panel element (3) with microslits (5) therethrough, said microslits (5) having a minimum slit width (b) of less than 0.45 mm. When in use, the panel element (3) is arranged with a distance to a rear surface.