Sound The main characteristic of sound-absorption materials are: the cellular structure and the porosity. So when an incident sound-wave hit a material, a part will be reflected and a part absorbed from the cellular structure of the material moving the air mass containedin the alveolus. The relation between the absorbed energy and the one reflected is the acoustic absorption coefficient. Acoustic Impedant The main characteristic of the acoustic-impedant materials is the same as the sound-absorption one, but with the addition of lead, rubber or charged PVC sheet. EUROFOAM designes, produces and sales sound-absorption and acoustic-impedant products and materials assuring the sound levels requested by the laws.