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Step 7Sound treatment theory
Most of what I know on this subject comes from Mitch Gallagher's Acoustic Design for the Home Studio. It goes into just the right amount of detail for a laywoman like me. Good explanations and helpful diagrams so you can understand difficult concepts without a Phd. I highly recommend reading this book before building your studio -- but if you don't, these online articles are informative, or here are a few sound tidbits (and I hope I won't mess this up... I can't find my book anymore so this is all memory... please feel free to comment if I've made mistakes):
Sound is a vibration. Waves. These sound waves have different frequencies (the length of the wave) High pitch sound has a high frequency, low pitch sounds have very long waves. Volume is determined by the height of the wave. As these sound waves travel through space they loose energy (volume). This is why low frequencies travel much longer distances and can go through walls: if the width of the wall is only a fraction of the size of the sound wave, it will loose much less energy passing through than if the sound wave is smaller than the wall. Plus an identical number of vibrations will carry the low frequency much farther than a high pitched noise.
When a sound wave hits a surface different things happen, depending on the surface (and the wave's frequency): it can either go right through (for example, with panels designed to absorb sound) and as it does some of its energy (volume) is dissipated as heat, or it bounces back (most of it, at least) if it encounters a smooth, massive obstacle, like a soundproofed wall. This is why soundproofing and sound treatment are contradictory goals: to soundproof you want to block the sound waves (which keeps them in your space till they die out), and for sound treatment you're trying to get rid of the unwanted reflections.
With all these sound waves bouncing around we run into the problems of comb filtering, nodes, room modes: depending on the size of the room and the frequency of the sound wave, as it bounces off the wall it can either cancel itself out or become amplified. I won't go into this and I chose to ignore nodes and modes completely because I had no control over the size of my room. I had enough other things to worry about. It is interesting to learn about, but unless you're building from scratch I'd advise to focus on ways you CAN improve your room.
There are two ways to tackle reflections: absorption, which diminishes the volume of the reflections, and diffusion, which scatters them. In both cases it's fairly easy to handle the mid to high frequency waves, but the low frequencies will be a problem. You also want to keep a good balance. You want to reduce reflections at all frequencies but you don't want to cut them out entirely or the room will sound dead.
Sound is a vibration. Waves. These sound waves have different frequencies (the length of the wave) High pitch sound has a high frequency, low pitch sounds have very long waves. Volume is determined by the height of the wave. As these sound waves travel through space they loose energy (volume). This is why low frequencies travel much longer distances and can go through walls: if the width of the wall is only a fraction of the size of the sound wave, it will loose much less energy passing through than if the sound wave is smaller than the wall. Plus an identical number of vibrations will carry the low frequency much farther than a high pitched noise.
When a sound wave hits a surface different things happen, depending on the surface (and the wave's frequency): it can either go right through (for example, with panels designed to absorb sound) and as it does some of its energy (volume) is dissipated as heat, or it bounces back (most of it, at least) if it encounters a smooth, massive obstacle, like a soundproofed wall. This is why soundproofing and sound treatment are contradictory goals: to soundproof you want to block the sound waves (which keeps them in your space till they die out), and for sound treatment you're trying to get rid of the unwanted reflections.
With all these sound waves bouncing around we run into the problems of comb filtering, nodes, room modes: depending on the size of the room and the frequency of the sound wave, as it bounces off the wall it can either cancel itself out or become amplified. I won't go into this and I chose to ignore nodes and modes completely because I had no control over the size of my room. I had enough other things to worry about. It is interesting to learn about, but unless you're building from scratch I'd advise to focus on ways you CAN improve your room.
There are two ways to tackle reflections: absorption, which diminishes the volume of the reflections, and diffusion, which scatters them. In both cases it's fairly easy to handle the mid to high frequency waves, but the low frequencies will be a problem. You also want to keep a good balance. You want to reduce reflections at all frequencies but you don't want to cut them out entirely or the room will sound dead.
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