The Standing Wave

Hey, there!

Where in your home you choose to record your auditions (and record actual work, like when you get booked and you use your home studio and equipment) can have very different acoustics depending upon how that space’s walls, floors and ceilings are treated.

But none of those treatments will soundproof the room. So why use foam at all?

Why all that foam on the walls?

Countless times, a student or client has come to me, proud of the fact that he or she has finally outfitted that second bedroom with acoustic foam, egg crates, carpet or some other treatment.

And sooner or later, they come back to me, trying to figure out why they still hear street noise, airplanes and helicopters overhead, or their neighbors having loud sex, all of which ruins their auditions and production.

Why?

Because wall, floor and/or ceiling treatments don’t keep sound out. They just minimize the repetitive, wacky bouncing of sound around the room.

[tweet_box]Acoustic foam doesn’t keep sound out. It just lessens reverberance in the room.[/tweet_box]

Exercise: Go in any bathroom, with its hard surfaces, tile, mirrors and tubs and showers, and say, loudly, “Ah HAH!” and listen to how long it takes for the sound to decay back to silence.

Then, mosey over to your walk-in closet, with its hanging clothes, irregular surfaces, shoes, ties and so on, and do the same thing. Your shout dissipates pretty quickly compared to the bathroom.

Yet, in both rooms, you can hear planes and air conditioning and those neighbors from outside the room.

(Not that I’ve been in your closet or bathroom.)

When you speak, those repeating “standing waves” of sound are heard by your mic, then absorbed in your recording space by putting treatments on the interior surfaces of rooms, but that treatment does not keep exterior sounds out of that treated space.

That requires isolation from exterior sounds – a barrier of air or water surrounding the room is best. That’s why radio stations and recording studios are built as rooms-within-rooms, and why WhisperRoom and Studiobricks installs work – it uses the air that surrounds it in the room in which you place it as that barrier.

Hope this helps.

David

Responses

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  1. Great distinction, thank you. Question – if I were to build a recording studio within an existing room, how much air space would be ideal between the walls?

  2. Excellent reality check about acoustics, and it can be even worse. I’ve had no success dampening sound in current digs – a closet “studio” I’ve placed within TWO sets of interior walls. My apartment is in a very old building with some (beautiful) stain-glass windows that let in heat in summer, cold in winter, and noise all year. Problem is compounded by rock-hard plaster-on-lath walls that bounce sound more readily than wallboard. My small-town retirement site is much, much noisier than even my former LA neighborhood; another move is in order as soon as affordable. Granted my experience is extreme, but people should understand the folly attempting to completely eliminate noise from their general living space. David, as always, a great, relevant post.

  3. You make the science of things so easy to understand. And I confess I love the little chuckles you insert so randomly. My WhisperRoom does a pretty good job of minimizing outside noise like my fridge or overhead footsteps, but it’s no match for garbage truck drive-bys or my neighbor’s driving bass-heavy speakers. Is there anything I can do about those facts of life?

    1. Switch to a Studiobricks room. It is much quieter – other than that, it depends on where in your house you have your room, and what you can do to add airspace between you and the noise.

    2. Those low frequency sounds are very difficult to control and block out. Fortunately with those sound you can usually filter them out with a “low cut” or “high pass” filter. Either with your software or directly on your mic if there is that feature. With my voice I can generally roll off everything lower than 100 hz. For the female voice you may be able to push that a bit further up and get rid of all that rumble that the booth can’t stop.

  4. Rain drumming on the felted flat timber roof was my issue here in western UK. Pretty much cured, along with other random noises, by loose-laying very heavy rubber playground tiles up above, outside.

  5. My understanding has always been that you need to get something in the way of the noise vibration…something to disrupt the flow. Obviously the air and water solutions work the best. Barring the Studiobrick…materials like Mass Loaded Vinyl (MLV) a dense rubber like material, can also work. My foam is glued to foam core panels and hung in my space. I’ve thought that the MLV could be attached to the other side. It could work.

  6. Yeah, it took me a while to get my booth’s interior acoustics to sound right. I got a commercial isolation booth, which is pretty good (not perfect) at keeping outside noises out. Rumbles are toughest, but those often are below voice frequency, so if I high-pass above around 40-50 Hz, I’m fine.) The trick was the corners; until I addressed that, it still sounded “roomy.” Not an actual echo, but a rise at around 120 Hz in my case, that gave a boxy sound to my baritone voice. Nice, big panels of Owens-Corning 703 wrapped in acoustic fabric covered most of the walls, which took me probably 80 percent of the way. But it wasn’t until I put proper 1’x1’x2′ bass traps in the wall and ceiling corners that I finally had the sound I needed. If you can’t seem to get rid of that boxy sound, try standing with your mouth 12-18″ from the corner, and hum a low note or two. If you hear a boxy reflection, you need bass traps! Have fun!