ABSTRACT
Typical porous absorbers are carpets, acoustic tiles, acoustic (open cell) foams, curtains, cushions, cotton and mineral wools such as fibreglass. They are materials where sound propagation occurs in a network of interconnected pores in such a way that viscous and thermal effects cause acoustic energy to be dissipated. As discussed in Chapter 1, they are used widely to treat acoustic problems, in cavity walls and noisy environments to reduce noise and in rooms to reduce reverberance. This chapter will detail the physical processes producing the absorption and theoretical models for predicting absorption properties.
