![]() Most practical approaches to soundproofing rely on some form of double structure with an integral air gap. This allows a large wall spacing to be used while still allowing the space to be useful. Obviously there's a choice of sacrificing some isolation and building the walls much closer together, or losing a lot of space.įigure 3: Spacing two walls apart.In professional studios, corridors around the studio area are often designed as part of the sound isolation strategy. Far enough, in this case, means several feet. As usual there's a catch to get this sort of figure, the walls have to be spaced far enough apart so that the air between them doesn't couple the energy from one wall to another (Figure 3). Double Wallsįigure 2: Double-thickness Wall.If a single wall can provide a reasonable degree of isolation, would two walls, separated by an air gap, be better? After all, if you add the 45dB for one wall to the 45dB of the other, you'd end up with 90dB of isolation - which should keep just about anything in or out. While 45‑50dB of isolation is a useful figure, there's no way you'd actually call it soundproof - as you'll know if you've ever lived next to noisy neighbours separated only by a single wall. ![]() Tables giving figures for the most common building materials are available for example, a single brick wall provides around 45dB of isolation while a double thickness, solid wall provides around 50dB (Figure 2). For every octave drop in frequency, the isolation provided by a wall is halved - which is why, when you walk past a night club playing loud music, most of what you hear is bass.īecause the acoustic attenuation of a wall or partition is frequency‑dependent, sound isolation is often measured in dBs for a range of frequencies averaged over the range 100Hz to just over 3kHz the resulting figure is termed the Sound Reduction Index or SRI of the material. Also important is the fact that soundproofing becomes less effective at lower frequencies. Reverberation is simply the audible result of the sound energy bouncing from surface to surface, the reverb dying away as the energy is finally absorbed.įigure 1: Single wall.Unfortunately, for a wall to be a good isolator of sound, it has to be heavy (Figure 1) - if you double the mass of a wall, you'll roughly halve the amount of sound transmitted. Of course, any reflected sound must eventually be absorbed somewhere, and if too much sound is reflected, the room becomes excessively reverberant. What keeps sound in also keeps it out, and the simplest form of sound attenuator is a solid wall, which will both reflect and absorb some of the sound. ![]() Sound IsolationĮfficient soundproofing relies, in part, on providing an effective way for the sound energy to be converted to heat before it escapes. The sound energy is converted to heat by this process, though the amounts of heat involved are extremely small. ![]() Sound energy is absorbed by surfaces, such as walls, furniture or people, and also by the very air that it passes through. The law of conservation of energy tells us that energy can neither be created nor destroyed it can only be converted from one form to another. Sound is simply vibrational energy using the air as a medium, but it can also propagate in liquids and solids. Actually, the term soundproofing is rather misleading, as it could be argued that nothing is truly soundproof - the correct term is sound isolation. However, room acoustics is an important topic in its own right and we shall be covering it as soon as soundproofing has been dealt with. It is vitally important not to confuse soundproofing with acoustic treatment - sticking foam tiles or egg boxes to your walls may produce a better sounding room, but they won't make any significant difference to the level of noise escaping. Professional studios employ elaborate soundproofing techniques to cut down on unwanted noise, both getting out and coming in, but there's a lot you can do for yourself if you're prepared to try your hand at a little DIY. One man's music is another man's noise, and the likelihood of the former being categorised as the latter increases as day runs into evening. Whether you run a home studio, a commercial studio or simply a MIDI sequencing system, the end result emerges from a pair of loudspeakers - and that's where your problems start. This month, the emphasis is on measures you can take to soundproof your studio or practice room. SOS begins an in‑depth series on practical studio design.
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