I often hear voice-over talents talking about soundproofing their room or their booth, when what they’re doing is not actually soundproofing. They’re only adding materials that will help to absorb sound. You might be thinking, “Robin, isn’t that the same thing?”
Not exactly. So let me break it down for you as simply as I can in this short blog -here we go!
There are two types of materials: Absorbing and Blocking. Let’s break it down.
Absorbing materials help with noise that’s within the room where you are. They help to improve the balance within the room, as well as get rid of any residual sound, bounce, or echo. By doing that, they enhance the quality of your speech, giving you a cleaner, clearer recording.
Blocking materials help block noise that is outside of the room where you are. We can break this into two kinds of noise. First, there’s airborne noise; think traffic, voices, TVs, or music. We also have what we call impact noise; this could be the rattle of a heavy truck going by, vibration from appliances, footsteps, or maybe Aunt Myrtle doing aerobics in the next room.
When we combine both absorbing and blocking materials, this helps with the noise within our space that’s bouncing around, and the noise outside of our space that’s trying to creep in. So, combining both gives us the best results toward soundproofing. Get it? I’m going to give you some examples of each and then the picture will be a little clearer for you. But first, I want to let you know about the rating system, which will give you a little more knowledge when you’re buying materials for your space.
When you’re shopping for materials that absorb sound, look for an NRC rating, which stands for Noise Reduction Coefficient. This shows how much an acoustic product can absorb. It’s kind of like how a sponge absorbs water. The ratings range from zero all the way up to…1. So, if a product has a rating of 0, it absorbs nothing. If it has an NRC rating of 1, that’s great! It absorbs everything. And we can have all the levels in between. For instance, a rating of .95 means the material absorbs 95 percent.
There is also something called an STC rating, which stands for Sound Transmission Class. This rating is more for sound blocking materials. It came about in the early 60’s, and it shows how much a particular material can reduce the decibel level of a noise. The higher the number of the rating, the less noise can penetrate through that material. The lower the rating, the more sound is going to get through. Boom! Now you’ll be an expert when you’re shopping.
OK, so let me give you some examples. If you’re looking for materials that are absorbing, you would be researching items like acoustic foam, acoustic panels, carpet, and acoustic fabrics (like Audimute). When you’re shopping, don’t forget to look for the NRC rating. If a deal is too good to be true, it probably has something to do with the quality, which will be reflected by the rating and probably the cost.
Here are some examples of sound blocking materials. There are acoustic coatings, like Mass Loaded Vinyl (MLV), which was developed for factory settings around pumps and loud machinery. It’s also used on mega-yachts around engine rooms to keep the living areas quiet. In addition to acoustic coatings, there are decoupling products. What does decoupling mean? Decoupling is when we structurally isolate or separate our materials; because whenever things touch, sound travels through. So, we want to improve our sound blocking performance by decoupling. There are isolation clips, which separate double and triple layers of drywall, and there’s a really cool product called Green Glue, which you can spread between two layers of drywall and it dissipates up to 90 percent of the noise. Be careful though, this audio blocking green slime can be a little messy.
So, we’ve talked about both sound absorbing and sound blocking materials, but you might be wondering if there are any products that can do both? Because remember, when we absorb and block, we get the best soundproofing. Guess what? You’re in luck.
Sound insulation works to absorb as well as block sound and it comes in three different forms. It goes between your walls and studs, and it helps to stop sound from entering or leaving your space. There’s what we call Mineral Wool or Stone Wool. It was discovered in Hawaii in the 1800’s, and it’s actually a biproduct of volcanic activity. How cool is that? It’s fire resistant and can withstand temperatures up to 1800 degrees. Not that we need that in VO, but if you happen to be a hot talent…ok, that’s it for my jokes. Next is fiberglass insulation, which you can get at Home Depot or Lowes, if you want the lower price point. It’s your standard building insulation, such as R-13 or R-19. If you want to go higher quality there’s Owens Corning 703 and the ATS acoustic rigid. And with fiberglass, don’t forget to wear gloves. Finally, we have cotton insulation. I prefer this as the cost is lower than the Mineral Wool, you don’t need gloves (like you do with the fiberglass), and according to HGTV- cotton insulation has NRC ratings that are 30% higher than fiberglass insulation. With insulation, in addition to helping to soundproof your recording area, it will keep your space cooler in the summer and warmer in the winter. Bonus.
So, if you want to really work on soundproofing your space, include not only sound absorbing materials, but remember the sound blocking materials as well. Keep an eye out for those NRC and STC ratings, whether you’re putting your recording space together for the first time or perhaps upgrading the space you have.
I hope that you can use this information on sound absorption and sound blocking to help you achieve soundproofing. May you have a cool space, be a hot talent behind your mic, and above all, have fun!
