Locally Reacting Materials

The concept of a locally reacting material is often used because it simplifies theoretical anaylsis. A locally reacting material's acoustic impedance is independent of angle of incidence. Thus the behaviour of sound at a particular point on a materials surface is not affected by the sound at other points nearby. Most porous absorbers can be approximated as locally reacting because the attenuation of sound in the material is sufficiently high to reduce lateral transmission. But an airgap can not be considered locally reacting and so Zorba can not model absorber systems with significant airgaps.