Recent Trends in Porous Sound-Absorbing Materials

Sound-absorbing materials absorb most of the sound energy striking them, making them very useful for the control of noise. They are used in a variety of locations - close to sources of noise, in various paths, and sometimes close to receivers. Although all materials absorb some incident sound, the term acoustical material has been primarily applied to those materials that have been produced for the specific purpose of providing high values of absorption. The major uses of absorbing materials are almost invariably found to include the reduction of reverberant sound pressure levels and, consequently, the reduction of the reverberation time in enclosures, or rooms. A wide range of sound-absorbing materials exist. In the 1970s, public health concerns helped change the main constituents of sound-absorbing materials from asbestos-based materials to new synthetic fibers. Although, these new fibers are much safer for human health, more recently, issues related to global warming may increase the use of natural fibers instead of synthetic ones.