Acoustic Foam - what is it and how does it Work

Acoustic Foam is a porous sound absorber

Absorbing sound spontaneously converts part of the sound energy to a very small amount of heat in the intervening object (the absorbing material) , rather than sound being transmitted or reflected.There are several ways in which a material can absorb sound. The choice of sound absorbing material will be determined by the frequency distribution of noise to be absorbed and the acoustic absorption profile required.

Porous acoustic foams physical properties

Porous absorbers, typically open cell acoustic foams , absorb noise by friction within the cell structure.Porous open cell acoustic foams are highly effective noise absorbers across a broad range of medium to high frequencies foam falls into two manufactured groups both polyurethane one being polyether and one being polyester please look for NRC data on any foam that is accredited as being an acoustic foam as some polyester foams are packaging foams and totally unsuitable for acoustic applications as are some polyether foams such as those grades used for bedding and upholstery cushions. the one certain way to know if a foam is suitable is to see the noise reduction coeficient data for the individual tiles or bass traps across a full frequency range tested. Foam manufacturers of both polyester and polyether make acoustic foam grades with the physical properties needed to give optimum acoustic absorption. The exact absorption profile of a porous open cell acoustic foam will be determined by a number of factors including the following:

• Cell size
• Torosity
• Porosity
• Material thickness
• Material hardness
• Material density

Below is an image of an acoustic foam Corner Bass Trap