ACOUSTIC TREATMENT FOR HOME STUDIOS
Part 1: Soundproofing
Silence is golden, or at least pretty expensive. Commercial recording studios cost hundreds of thousands of dollars to build because they must allow absolutely no sound to enter from a usually noisy urban environment. Double and triple walls, isolated concrete slabs, custom steel doors are all standard but high priced items used in their construction. A studio's sound is its number one asset and most owners will go to any lengths to get it right.
Luckily, electronic music does not normally require the extreme isolation needed for recording live ensembles. The use of microphones is infrequent enough that it can be scheduled for predictably quiet times, and close mic techniques, (which are usually appropriate for sampling or vocal lines) don't pick up much noise. Given a reasonably quiet, solidly built house to start with, a decent home studio can be created with modest expense and effort.
Sound can travel through any medium-- in fact it passes through solids better than through air. Sound intensity is reduced in the transition from one material to another, as from the air to a wall and back. The amount of reduction (called the transmission loss) is related to the density of the wall-- as long as it doesn't move in response to the sound. Unfortunately, all walls are somewhat flexible. Any motion caused by sound striking one side of the wall will result in sound radiated by the other side, an effect called coupling. If the sound hits a resonant frequency, the wall will boom like a drum. Most isolation techniques are really ways to reduce coupling and prevent resonances.
The most effective soundproofing must be designed into a house when it is first built. A typical residential wall is made of a frame of 2x4 wood studs covered with 5/8" thick gypsum board. Properly built (no holes!) this will provide about 35 dB of isolation. Fiberglas filler, R-7 or better, will...