Soundproofing – Page 2 – www.audioproductcreators.com

As wood is a dense material, the noise reduction is smaller than porous materials such as mineral wool and fiberglass batts. To know how much a wood board can help reduce noise, it’s necessary to take into account the NRC (absorption coefficient), and the STC rating (amount of noise reduction of a barrier material). The best results can be achieved using a 5/8” soundproof drywall board in 3 layers plus 3.5” fiberglass or mineral wool, which will reduce 60 dB on average. The thickest the wood layer and insulating material the more noise it will reduce. Here is a list of how much noise drywall and plywood can reduce, according to their thickness: Wood BoardThicknessNoise reduction (dB) using a sound meter appSTC Noise reduction provided by a barrier materialAbsorption coefficientNRC2 Drywall ½” layersOne on each side of the wall33 dB330.302 Drywall ½” layersOne on each side of the wall PLUS fiberglass insulation inside39 dB390.652 Drywall ⅝” layersOne on each side of the wall PLUS fiberglass 3.5” insulation inside40 dB47+0.702 Soundproofing Drywall ⅝” layersPLUS 4” (or more) mineral wool60 dB60+1.002 Plywood ½” layersOne on each side of the wall20 dB200.25 Wood boards are one of the most common materials for studs and blocking walls to reduce noise. It’s widely used in sound studios and sound booths for recording audiobooks and podcasts. Dry wood is a very poor electricity conductor (10-16σ (S/m) at 20 °C). Thus wood becomes a useful and safe material. Drywall Types for Sound Insulation Purposes The best sound reduction wood type is the one that provides 2 1/4“ layers of gypsum drywall plus an inner layer of sound-absorbing polymers. Standard drywall is a very common low price material used for thermal acoustic insulation. The following types of drywall can be used to make a sound booth, as well as to reduce noise from adjacent walls. Blue Board Drywall (STC 33 - 35) The principal feature of a blue board is its moisture-resistant property provided by plaster applied on the board and then covered with paper. A single ⅝” layer of Blue Board provides STC 33Two ⅝” layers of Blue Board provide STC 35 Difference Between Blue Board and Drywall The main difference between Blue Board and Drywall is the kind of paper they are covered with. In drywall, the purpose of the paper is to offer a suitable surface for standard paint, whereas in blue boards the purpose is to facilitate the application of veneer plaster coating. Type X (STC 39 - 48) The main characteristic of Type X drywall is its fire-resistive gypsum core. A single ⅝” layer of Type X provides STC 39Two ⅝” layers of Type X provide STC 48 Soundproof Drywall (STC 64 - 80) What makes this type of drywall a very good noise reduction material is its composition: 2 layers of ¼” thick gypsum drywall1 inner layer of viscoelastic sound-absorbing polymersTotal thickness: ⅝” Although the price is substantially higher than a regular drywall panel, one single soundproof drywall layer equals on average the noise reduction of 7 layers of standard drywall, but with the weight of only 3 layers. This can reduce handwork fees and installation time. Excellent examples of this type of drywall are: SilentFX® QuickCut by CertainTeed (STC up to 56)Sound Break XP by National Gypsum (STC up to 64)QuietRock 545 (STC up to 80) What to Avoid When Making a Sound Booth In spite of investing in the best noise reduction materials, there are three common mistakes that can decrease the performance of the sound insulation you try to reach in your sound booth: Leaving gaps between the wood boards: every single crack and unsealed edge can allow some noise to break into the sound booth. As condenser microphones are a must when recording professional-quality audio products (audiobooks, podcasts, voice-over for TV, films, audio courses, audio for Youtube videos, and more) there is a big chance to get unwanted noise in your recording. Make sure every wallboard is perfectly glued, taped, and sealed, so you won’t experience any downsides when proving how good your work was. Use only sound absorbers and no insulating materials: Absorbing materials such as Auralex panels are excellent to minimize any reverb or echo inside the booth. But they do nothing to insulate the recording space from noise coming from outside. Although being in a basement is one of the best scenarios to make a sound booth, if you want no other worries and further fees to fix sound leakage, consider adding at least a layer of mineral wool on the outer sides of the sound booth. Better safe than sorry. Use reflecting materials when you want sound absorption: The more dense a material is the more reflection it will cause. In many sound booth designs, a small window can do no harm. Just make sure the inner walls are properly covered with absorbing foam. Things to Remember When Making a Sound Booth Forgetting ventilation: It’s common to disregard setting appropriate ventilation in the sound booth. If you consider working on short projects like commercials, corporate material, and voice narration under 1000 words, you may conclude that the job can be done in a few minutes. That can be true if you record only a couple of gigs per day. If you stay in a sound booth for more than 30 minutes you will definitely notice that ventilation is necessary. Watch how to install ventilation in a sound booth: https://www.youtube.com/watch?v=4eMh1a4c1oY https://www.youtube.com/watch?v=eFUtV7N7pJE Using computers inside the sound booth: The fan noise can be easily caught by your microphone, and that kind of unwanted sound is really tough to get rid of. An alternative can be making a sealed window in the sound booth so you can place the computer outside the booth but have the keyboard and mouse inside, on a small desk. Glass is a reflective material, therefore you need to make sure that the window is just big enough to let you see the screen. To avoid the computer fan noise, I use a portable Zoom H4N recorder, a music stand to place my iPad, a mic stand, and a Rode NT1A with a pop shield and a clip lamp on the music stand which I also cover with an absorbing cloth, like a towel. To make the recording process as smooth and efficient as possible, I use a dog clicker to make a big wave pattern that helps me recognize mistakes. Thus the editing stage is much easier to do.