ACOUSTICAL MATERIALSBy:MUTHUVEERAPPAN.C

DEFINITIONCOMMERCIAL and CUSTOM DESIGNED building materials and surface treatment which contribute significantly to acoustical control or to noise reduction

METHODS of ABSORPTION

General Classifications:ACOUSTICAL MATERIALS

POROUS MATERIALSSoft, porous materials are very good sound absorbers. The basic acoustical characteristic of these materials is a cellular network of interlocking pores. Within these pores, incident sound energy is converted into heat. Examples of these include acoustical boards, diffusers, soft plasters, mineral wool, and acoustical blankets, among others.

POROUS MATERIALSCharacteristics:Their sound absorption is more efficient at high, rather than low frequencies. However, their acoustical efficiency improves in the low frequency range with increased thickness and with distance to their solid backing

POROUS MATERIALSCategories of Commercial Materials:Various types of perforated, fissured, or textured materials constitute typical units in this groupCommonly used materials include:

ACOUSTICAL BOARDSThese can be installed in several ways:

ACOUSTICAL BOARDS

ACOUSTICAL BOARDS

ACOUSTICAL BOARDS

ACOUSTIC HANGERSAcoustic Hangers or baffles- a system of fiber-board panels that are wrapped with insulation and are hung freely using wire or rope. Sample of Acoustic Hangers

ACOUSTIC HANGERS

GEOCOUSTIC TILES and PANELSGeocoustic Tiles- special prefabricated units for random application on walls and ceilings.

GEOCOUSTIC TILES and PANELS

GEOCOUSTIC TILES and PANELS

DIFFUSERSDiffusers- absorptive material that have, irregular surfaces, or angled or curved fronts, so when mounted on a wall or the ceiling they stop parallel wall interference and prevent standing waves.

DIFFUSERS

PLASTERS and SPRAYED-ON MATERIALSAcoustical Plasters and Sprayed-on Materials: Absorbent paint applied in a semiplastic consistency. There are two types:

ACOUSTIC BLANKETSAcoustic Blankets- Also referred to as Isolation Blankets. Materials manufactured from rock wool, glass fibers, wood fibers, hair felt, etc.

ACOUSTIC BLANKETS

ACOUSTIC FOAM BOARDSAcoustic Foam Boards- High density blankets with covering; also act as diffusers

ACOUSTIC FOAM BOARDS

CARPETS and FABRIC

PANEL ABSORBERSPanel Absorbers- Also referred to as Membrane Absorbers. Impervious material installed in a solid backing but separated from it by an air space.

CAVITY RESONATORSCavity Resonators- Also referred to as Helmholtz Resonators. Materials that consist of an enclosed body of air, confined within rigid walls and connected by a narrow opening to the surroundings space.

INDIVIDUAL CAVITY RESONATORSIndividual Cavity Resonators- Standard concrete blocks, using regular concrete mixture, but with slotted cavities

PERFORATED PANEL ABSORBERSPerforated Panel Absorbers- Perforated panels spaced away from a solid backing

SLIT RESONATORSSlit Resonators- Isolation blankets (or alternative) covered with slits, the whole system forming a resonator

SLIT RESONATORS

SPACE ABSORBERSSpace Absorbers- Sound absorbing objects which are suspended from the ceiling, used when regular boundary enclosures of an auditorium do not provide a suitable or adequate area for conventional acoustical treatment.

VARIABLE ABSORBERSVariable Absorbers- Sliding, hinged, movable, and rotatable panels constructed to expose either absorptive or reflective surfaces.