Imagine an ocean wave hitting a flat concrete storm wall, it’s going to bounce off and go back out to sea unaffected. That’s what a drywall or concrete wall, metal ceilings or any hard surface does to a sound wave that hits it. It takes a soft, porous material to slow down and absorb that sound energy.
Sound absorbing does just that, it allows sounds to be heard more clearly and reduces echoes and reverberations in your space. Absorbent foams and fabrics are ideal for acoustical control. While it is important to note that absorbing materials do not stop noise from travelling between rooms they are often used in conjunction with sound insulation which prevents noise from passing through walls and other partition surfaces.
Improving Acoustics: The Science of Sound Absorbing Materials
When sound waves hit a fabric or absorbent foam they enter the pores of the material, much like a sponge does with water. This enables the sound waves to lose some of their energy through friction against the pores, and some of that energy is converted into heat energy. This change in energy dissipation makes it impossible for the sound waves to bounce off the fabric and into another surface in your room, which causes reverberations and echoes.
The acoustic properties of a fabric or absorbent material are typically described using a rating known as the Noise Reduction Coefficient (NRC) in a certain frequency range. A higher NRC number indicates a greater ability to absorb sound at that specific frequency. However, not all fabrics have the same acoustic properties and even the same fabric may perform differently in different settings.