Getting Your Room Acoustics Right

By Jacob Horney, Sound Engineer, VoiceArchive

Let me state what a lot of voice talents seem to forget; the need for a recording environment to be acoustically well trimmed really surpasses the need for high-end recording equipment. This also means, that you can breathe new life into your current recording setup simply by making sure that the acoustics of your recording area have been properly addressed.

The biggest problems preventing great sound

At VoiceArchive, one of the biggest problems we experience when receiving recordings from our voice talents is unwanted reverberation caused by a lack of room treatment. Reverberation on a recording will not only initially sound bad, especially when compression and other processing is applied in post production, but it also makes editing, e.g. cutting out breathings or words in the middle of sentences, very difficult – and in worst case impossible. Most importantly, it greatly reduces the variety of applications in which your recordings can be used.

Low frequencies tend to be the biggest problem, especially in smaller rooms with response variations as large as 35 db (which is A LOT). Maybe some of you voice talents have experienced that the low frequencies on your recordings sound muddy, so naturally you reach for your EQ to scoop out some of the low frequencies. Maybe this doesn't even do the trick so you engage the low cut filter on your microphone or on your mic preamp. This takes care of the muddy low end frequencies on your recordings but leaves your voice sounding thin and cheap – also, once these frequencies have been removed from a recording, they can never be restored again. What most people probably don't know is that in many cases, you are able to keep the low frequencies and even get a nice bottom end on your recordings even without applying any EQ. This is done simply by making sure that your acoustics are right.

Many voice talents think that installing thin acoustic foam all over their walls is sufficient. After all, if you clap your hands in a room treated with foam (or fiberglass, blankets or egg crates), you don't hear any reverberation or flutter echoes. Still, thin treatment does nothing to control low frequency reverberation or reflections, which hand claps won't reveal. Basement studios and rooms having walls made of brick or concrete are especially prone to this problem. The more rigid the walls are, the more reflective they will be at low frequencies. Actually, simply building a new sheet rock wall a few inches inside an outer cement wall (filling the space with fiberglass insulation) will reduce reflections at the lowest frequencies drastically.

Easy practical measures to improve your sound

In the following, I will be giving some advice on what practical measures you can take to improve the acoustics in your room without getting too much into theory and the laws of physics. I will be skipping a few steps here and there for the sake of not losing anyone on the way. Also, I will not be giving too detailed descriptions about why the steps below work (I just ask you to take my word for it), but further down in this article, you will find some useful links if you wish to venture even further into practical acoustics. You will be able to read up and fill the theoretical gabs, which this article may leave you with.

In dealing with tuning the acoustics of your room/vocal booth, your enemy no. 1 is things which will reflect sound. This can be anything from a wall, a computer monitor to a window, basically anything with a hard smooth surface. The harder the surface, the more reflection it will most likely cause. Secondary reflections, as they are called, will bounce of any hard surfaces in your room and then travel back and into your microphone, slightly delayed compared to the direct sound of your voice. This is in the worst case heard as reverberation on your recordings, and if it’s not heard as reverberation it will definitely make your sound muddy.

Getting your acoustics right requires that you stop reflections ranging from the lowest to the highest frequencies, dampening them as evenly as possible all across the frequency spectrum. There are a few easy but highly effective ways of getting this done. As a rule of thumb, you need something to absorb the sound waves and not reflect them back.

Broadband Absorbers

One thing you can use is broadband absorbers. These are made with rigid fiberglass (tightly weaved and compressed). You make a frame out of wooden beams (e.g. 2" x 2") so that you can fit a rigid fiberglass batt into the frame. The frame should by so tight that the batt will stay in place. Use cotton fabric that hasn’t been too tightly weaved (you should be able to blow through it) to cover the frame on both sides. Hang these squares on your walls with approx 1” between the absorber and the wall, and they should also hang straight across from each other (see picture below).

Even though broadband absorbers are really effective, they lack the mass and the ideal placement to effectively stop the lowest frequencies. Therefore, for this purpose we need to build bass traps.

Bass Traps

Bass traps are the most effective way of controlling the low frequencies if the sheet rock wall mentioned earlier does not do the trick. Bass traps are made out of chunks of regular fiberglass (insulation) cut into triangles and stacked in the corners of your booth/room from floor to ceiling. Then, you make a frame of e.g. 2” x 2” wooden beams to cover the fiberglass stacks. Next, you stable some fabric on the frame and use the frame to cover the stacked insulation as shown on the pictures below.

There are also other highly effective measures to be taken when dealing with room acoustics but the above mentioned solutions are pretty easy to apply. These can be put together in one afternoon if you have all the materials at hand, and they will vastly improve your sound if you have a less than ideal room to work in.

Questions?

Right, so go to your nearest hardware store, get the materials, invite over a friend or two to help you out, and don't forget large quantities of pizza and soft drinks – this will exponentially increase your friend’s willingness to spend a Saturday working for you :-)

If you should end up with more questions than answers from reading this article, please don’t hesitate to write or call me (jacob@voicearchive.com or 0045 7022 7042). I will gladly do my best to answer any questions that may pop up along the way, and I will look forward to receiving even better sounding recordings from you guys and gals in the future. Please also feel free to let me know if you think you have a better way of achieving well sounding recordings.

Links for further reading:

Sound on Sound online:”Building a DIY Vocal Booth”

More Sound on Sound online on building a booth:

Recording Studio Design Forum:

Room trapping walk through by Ethan Winer: