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Don't throw out the baby with the bath water.

Don't throw out the baby with the bath water.
 Don't throw out the baby with the bath water.

When most people think about acoustic treatment they will picture egg crate foam, or fiber-filled panels of some sort. This is by far the most common approach to room acoustic treatment, and also to recording studio acoustics.

The basic idea of this approach is the elimination of reflections. If you were to set up your music or video system in nature on a flat plain or in the desert, everything you hear would be direct sound from the speakers. No reflections would complicate what we hear. This is an anechoic space: a space without echo or reflection.

But when you are in a room those pesky walls, ceilings, and floors, are all reflecting acoustic energy. Now if it were just six reflections (one from each of the walls, ceiling, and floor) this would be manageable. But in fact these "early reflections" become a series of complex interactions as they rebound across the room, and are reflected back and forth in a confused manner. Add in the corner effect where acoustic pressure is megaphone loaded back into the room and the basic desirability of some sort of acoustic treatment becomes clear.

The recording studio approach to the problem is to fill the room with broad band absorbing material - the more, the better -  to attempt to approach an anechoic space, like you would achieve outdoors in the desert. But in a listening room this dry, studio acoustic can seem sterile, overly dead, and basically unnatural given that most real acoustic spaces are not outdoors in the desert, but rather are concert halls, night clubs, theaters, and other environments which do reverberate.

For this reason the biggest challenge with traditional acoustic treatment products is to acoustically reign in the room without "killing" it.

In one sense this game seems by nature to be rigged against the user. Why? Because when dealing with bass frequencies, both in theory and in practice, more acoustic treatment will usually be better than less. In fact some acousticians would recommend starting by treating 30% of the surface area in the room with "bass traps" and then moving up from there. (You have probably seen photos of recording studios that have 50% or more of the surfaces treated.) One obvious problem is that most of us don't want 30% of the surfaces in our listening or theater rooms covered with acoustic panels. The direct acoustic problem is that "bass traps" will tend to absorb other frequencies as well, making the room too dead in the midrange and in the high frequencies.

Go Back to Main newsletters : Room Acoustics 201 - Part 3
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