Sound absorption using foam

When fixing the sound of a room, typically one uses some foam based product to help absorb sound reflections. There are many foam products out there, but they are not equal, and you should check with an audio professional for advice and guidance. However, the following are some basic pointers.

Do not use 'eggshell' foam. This is the foam that looks like a egg carton. Why? Most eggshell foam products are a) closed cell, and b) not flame retardant. In a closed cell foam, the sound cannot enter into the tiny cells, and much of the energy is reflected back into the room. And the lack of flame retardancy is a danger to life and equipment.

Instead, look for a professionally manufactured product for the correct purpose. Two of the larger companies are Sonex and Auralex. Both make sound absorbing panels and materials to help with your room. Most importantly, their products are open celled, which means that there are spaces where the sound energy can enter and get trapped. These products actually heat up as they do their job!

Equally important, their products meet national flame retardancy guidelines, hindering fire and smoke in your studio.

How to calculate the amount needed for your studio space? Well, the typical rule of thumb is 60% of the wall space should be covered to absorb the predominate amount of energy without sounding dead. The room should have a flat response, but still sound 'live' enough to mimic the average listeners environment. You don't want to create a complete anechoic chamber!

A vocal booth should require more foam, since you want as few artifacts in the recording as possible.

To make moveable gobos, you might want to adhere the foam to a solid backing material like Masonite or pegboard. You can then move the foam around to play with the sound in your space, or to create different reflective patterns. Another trick is to build a frame around the gobo and cover it with a loose weave, decorative scrim. This will allow the sound to pass through the weave, but still be absorbed by the foam behind it.

Hope this helps! For related articles, please click on our Sitemap, Soundproofing, Sound control part II, or Send us an email!