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Filed under: Audio •

Simple Soundproofing

We work at home. Our house has two levels; downstairs is half-jokingly referred to as “the studio complex.” We’ve set up one of the spare bedrooms down there as an audio room.

Most bedrooms are boxes with parallel walls, which in turn often cause problems with resonances and echoes in a room. Fortunately, the spare bedrooms in this house have some non-parallel walls, which help break up and diffuse the pattern of echoes, which makes them less annoying. Adding more hard surfaces such as computer desks and monitors can increase the amount of diffusion, but sound is still bouncing around. The result is akin to the reverberation present in what one would call a “live small room.” As we use a microphone placed about a foot away from our head instead of a headset mic (to cut down on the distraction, and also pick up sounds such as the keystrokes and mouseclicks), it picks up some of this room sound as well.

Although I personally like a little natural reverberation when I listen to a voice - completely dead rooms sound unnatural to me - a few have “commented on” the liveliness of the room sound in the voiceovers to our training videos, so I decided to see if I could tame the bouncing soundwaves a bit. I tried a cheap, low-tech approach first, then threw a little more money and work at it. I thought it would be fun to share my results:

Original Room

The above images show our audio room without any sound treatment. In addition to the walls, monitor, and computer furniture, there are also a few other hard surfaces present (keyboards and equipment racks), which add to the room’s lively, diffuse short reverberation. I use a Focusrite VoiceMaster Pro to process our voice, which includes a “downward expander” which tamps down extraneous sounds between sentences - but as you can hear from the recording below, the room’s reverberation is still audible (you might want to use headphones for the clearest results):

Low-Tech Approach

First I tried the cheap DIY approach of draping blankets over some of the hard surfaces in the room. This has the advantages of being inexpensive, easy to apply, and keeps dust out of the gear. As you can hear below, it had a small positive effect:

Slightly Higher-Tech Approach

Next I decided to try some “real” sound treatment materials. It’s important to me that our audio studio be an aesthetically pleasing place to spend time in, so I didn’t want to load up the walls with egg crates or sculpted foam squares. After a little research, I found Auralex ProPanels: fabric-covered panels of dense fiberglass. I bought a small set of 2’x2’ and 2’x4’ panels at a cost of roughly $400 to place on sections of bare wall that faced the computer desk recording position.

Mounting on the walls was easy (and let me sing the praises of WallClaw Hammer-In Drywall Anchors - much easier to use than normal plastic drywall anchors); the impaling clips Auralex includes allow the panels to be repositioned multiple times until you get it right. Mounting on the ceiling was considerably more difficult, especially since I decided to hang the heavier 2” thick 2’x4’ panel over my head. Although I did buy a set of Auralex Cloud Mounts, I wasn’t thrilled with hanging the panel some distance below the already-low ceiling; it seemed claustrophobic. I ended up going with a set of long toggle bolts and washers.

I was honestly stunned by how effective just four panels were:

To really hear the difference, listen to this side-by-side comparison of the wooden claves being struck in the differently-treated rooms (the voice is all from the final room):

My final step was going to be changing out the window treatments from the current plastic blinds to a pair of cloth roman shades, which should help absorb rather than reflect sound. However, the Auralex panels are already so effective in deadening the room that I have more freedom to rethink the window treatments, instead focusing on absorbing light (to make the room more consistent to record video in during the day and night) rather than sound.

Anyway - I thought I’d share this recent audio adventure before I settled down and got stuck into recording another set of After Effects training videos.

(FTC disclosure: I have no relationships with any of the companies mentioned above, and the only thing I received for free was my labor.)

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I am sorry if I missed the location, but I could not find the referenced audio files.

Interesting article.

Posted by .(JavaScript must be enabled to view this email address)  on  06/07  at  07:56 AM

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The audio files are embedded in the article - look for the QuickTime player bar (those long horizontal strips right after the description of what you’ll be hearing). They’ll take a few seconds to load; you may just see a small icon during loading before the full bar appears.

- Chris

Posted by Chris Meyer  on  06/07  at  09:04 AM

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Nicely done Chris. I immediately noticed the strong character of your room on Apprentice’s guide to AE. By the way, these tutorials are great, for what I need certainly the best,  regardless of sound quality.
The absorbers have removed a significant part of the mid/hi freq flatter echo of your room, and the speach is now more focused, with shorter reverberation time.

One thing however that can still be noticed is room mode, or standing wave between floor and ceiling, probably between 70 and 100 Hz, depending on room height. It is much more difficult to control, and audio studios usually have double ceilings because of this. Nevertheless, your room is now is much more recording friendly than before.

For those who can’t afford absorbers there are inexpensive portable vocal shields available which do a decent job isolating the vocal mic from the room, like this one:
http://www.soundkit.co.uk/acatalog/Acoustic_Solutions.html

Peter

Posted by Peter Gruden  on  06/07  at  03:16 PM

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Hi, Peter -

Thanks for the knowledgeable comments! I too noticed that the EQ of the room changed with the sound treatment. The floor is carpeted, which helps the floor/ceiling resonance a bit, and I was hoping that the volume enclosed by the blanket-covered racks would act as (weak) bass traps, but I may have to look at further touch-ups. I do know that lowering the panel over the computer desk will make it act more like a bass trap; that might be one solution…

However, another more immediate problem I have are my smaller monitors coupling with the computer desk to overly enhance their bass; some sort of pads (like the Soundkit SPK Isolators) may be required.

Speaking of which, the Soundkit vocal shields are interesting; in a rental house many years ago, I attached clips to the ceiling where I could quickly hang a blanket barrier around the mic position, giving a similar result.

thanks again -
Chris

Posted by Chris Meyer  on  06/07  at  05:57 PM

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its also worth noting the acoustic pattern of your microphone can have a dramatic effect on the amount of extraneous sound that gets picked up.

I’ve got a very sensitive Neumann U87 mic which i can change the polarity on, and i found that in my room (which is located inside a noisy warehouse building, and contains plenty of fan cooled kit) the best way to avoid the room sound is to switch to a figure of 8 pattern, with the back side of the mic inside the curve of an SE Reflection shield, the front side pointing at 90degrees to the noisiest fans, I can get some pretty clean sounding voice records.

adam

Posted by lightningad  on  06/08  at  05:24 PM

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Good point, Adam. I’m using an AKG C1000 set to hypercardiod mode in an attempt to focus better on the voice and reject fan noise etc. from the sides.

However, just as helpful in my specific case is that Macs have fortunately been getting quieter with subsequent revisions. Mine is also semi-boxed in the lower part of the rack to the left of the computer chair, with Sonex foam further damping and absorbing its sound.

Annoying is that I got a new LaCie “black cube” RAID to act as my Time Machine backup, but its fan is far too audible to leave on. That’s why I prefer LaCie’s tall aluminum fan-less case design.

- Chris

Posted by Chris Meyer  on  06/11  at  09:54 AM

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i have my macs in the room next door, but like you say they are really quiet these days.
My two noisiest gadgets are my time machine backup (which is just a single drive on the desktop), and my broadcast legalizer slotted into the front of my desk…i really dont know if they could have fitted a noisier fan to such a diminutive piece of kit!!

adam

Posted by lightningad  on  06/11  at  04:23 PM

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I know a friend who got QuietRock soundproofing drywall for his home studio, and it has worked out great. It’s cutting out more than 90% of the noise, and was a reasonable buy too! That’s another ‘free’ recommendation!

Posted by .(JavaScript must be enabled to view this email address)  on  06/24  at  12:23 AM

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