Just as we absorbing sound the moisture on a damp sponge when wiping up a grape juice spill, sound absorbing materials catch and change some of the energy that sound waves travel through. This energy is transformed into heat or another form of energy and the absorbing material helps to reduce noise, echoing, and reverberations.

In general, soft, pliable and porous materials (like cloth) serve as good acoustic insulators and absorb sound, while dense and hard impenetrable materials tend to reflect more than they absorb. However, the effectiveness of a material as an absorber can vary greatly depending on frequency. High frequency sounds have shorter wavelengths and are more easily absorbed by thinner materials. While low-frequency sounds have longer wavelengths and are more easily reflected or transmitted through thicker materials.

Quieting the Office: Strategies for Absorbing Sound

When sound comes in contact with a porous material such as acoustic foam or an area rug, it is absorbed and converted to heat energy causing it to decay much more quickly than a reflected sound wave would. The same principle applies to many types of fibrous material, including glass wool and rock wool insulation and even our natural feathers and furs.

As the density of these materials increases beyond a certain point, they start to lose their ability as an absorber and begin acting more like a soundproofing barrier. For this reason, acoustic panels and acoustic ceiling panels are usually made of open cell acoustical foam with specialized facings to ensure fire safety.