Sound absorption is when the sound strike the absorbent object and reflect, but the energy of reflection is reduced significantly.

The reduction factor can be from 1% (not effective) to 100% (very effective).

Materials and constructions made with foam, cloth, bass trap, pores like walls are capable of absorbing sound.

Porous Sound Absorbent Materials

Porous sound absorbent materials will be anything that can transmit sound through themselves and then absorb the sound, converting it into a small amount of friction energy. These can be items such as a carpet, heavy draperies and open-cell foams. Any item that will allow air to pass into it and then be absorbed by a cellular structure will make a good sound absorber. The best porous sound-absorber materials will be specifically made for sound absorption, such a thick foam pads or thick sound-dampening window drapes.

Panel Materials

Another way sound can be absorbed is by allowing the material to flex and reverberate, effectively absorbing and dissipating the wave. This is done with flexible panels such as thin wood or other non-rigid material suspended in a frame. Any large surface that has the ability to resonate with any sound that interacts with it can be used as a panel sound absorber. Panel materials are generally better at absorbing lower frequencies then porous materials.

Sound insulation, on the other hand, relates to the actual reduction in sound travelling from one area to another through a wall, floor or ceiling. Sound transmission in buildings results from both airborne and impact noise.

Airborne Noise

Airborne sound is generated typically from sources such as voices, Hi-Fi systems or TV sets, and travels through the air into the structure of a building, and out again into adjoining rooms.

Impact Noise

Impact sound is the result of physical excitation of the structure of a floor by impacts from footfall, moving furniture and dropped items.