Build Your Own Anechoic Chamber

For professional-level sound recording, you’ll need professional-level equipment. Microphones and mixing gear are the obvious necessities, as well as a good computer with the right software on it. But once you have those things covered, you’ll also need a place to record. Without a good acoustic space, you’ll have all kinds of reflections and artefacts in your sound recordings, and if you can’t rent a studio you can always build your anechoic chamber.

While it is possible to carpet the walls of a room or randomly glue egg crate foam to your walls, [Tech Ingredients] tests some homemade panels of various shapes, sizes, and materials against commercially available solutions. To do this he uses a special enclosed speaker pointed at the material, and a microphone to measure the sound reflections. The tests show promising results for the homemade acoustic-absorbing panels, at a fraction of the cost of ready-made panels.

From there, we are shown how to make and assemble these panels in order to get the best performance from them. When dealing with acoustics, even the glue used to hold everything together can change the properties of the materials. We also see a few other cost saving methods in construction that can help when building the panels themselves as well. And, while this build focuses on acoustic anechoic chambers, don’t forget that there are anechoic chambers for electromagnetic radiation that use the same principles as well.

Thanks to [jafinch78] for the tip!

15 thoughts on “Build Your Own Anechoic Chamber

  1. Which would you rather hear music performed in? A an anechoic chamber or B the Royal Concertgebouw or Symphony Hall Boston? Two of the worlds greatest sound spaces with fantastic reflections and ambiance. It’s Steely Dan versus live sound. Having been in one of A, the strangest thing I heard is when two speakers were in opposite corners and I stood in the center. The speakers went from being in the corners to sounding like they were on my ears like headphones.

    If I had binaural recordings to play through that it would sound great, but then I couldn’t move my head. Binaural beats the pants off of everything to come out of a studio. Now there are ways of doing HTRF on mono tracks and making them sound like they are live in 3D. Otherwise any number of mono tracks unless mixed this way aren’t stereo (solid). Pan pots don’t make stereo. I grew up up in the days of tri-phonic, LCR. Before then they had nothing at all in the center, just a big hole.

    I couldn’t get past the recorder solo on a merry go round (needs A-B comparison) much, but this testing seems to be for treble only. I know that foam is expensive and turns to dust or goo. If I heard that same solo in binaural in a live space there would be a lot of reflections and it would be obvious what I was hearing. Instead I heard a boring track of recorder sound isolated from reality space. Try using a Leslie in an anechoic chamber, it just doesn’t work.

    Earl Wild hauled a piano into one to record Liszt, many others went to Carnegie Hall.

    1. I like to think of the needs of an Anechoic Chamber like that of a Faraday Cage for lower frequencies. Depends on the system user requirements for the application.

      I guess the history of the performances with acoustic considerations goes back to Greek or pre-Greek theaters and Roman amphitheaters. Like the recordings themselves… they’re going after and for producing an effect:
      https://www.youtube.com/watch?v=LxksRFZacJI

      I learned recently of “Room Tone” in recording. https://en.wikipedia.org/wiki/Presence_(sound_recording)

      Interesting the characteristics of resonance in different applications:
      https://en.wikipedia.org/wiki/Resonance_(disambiguation)

      What you note reminds me of an answer to a Quora question last week I made in a comment to my answer:
      https://www.quora.com/What-are-the-disadvantages-of-resonance?

    2. The spare bedroom in our house isn’t anywhere near as big as Carnegie Hall, and we don’t use a Leslie…

      It’s easy to add reverberation after the fact (noting synthetic reverb is less satisfying than good venues), but it’s virtually impossible to reduce or remove.

      As the presenter mentioned, many scenarios would do with a small portion of wallspace covered. In a small room, phasing effects from primary reflection can be a real problem, though I agree that’s mostly about specific listening positions.

      In our case the problem was two facing walls. If you clap, you’d hear half a dozen (very rapid but distinct) echoes. Certain instruments sounded horrible. I bought some tiles of acoustic foam (on special), fitted 2 sets of 3 to thin plywood, and hung on the facing walls. Placing close to the centre of the wall was most effective, and the room much better to practise or record in. The floor was already carpeted. One other wall has a window with a curtain, and its opposite is irregular.

      I like the tips about the stiffness vs warping, the felt pads, and especially the observation that you may not need a completely lined anechoic chamber.

      1. Just in case I’ll not also that for those that didn’t read through the comments on the Youtube video post… there is great information in the comments section also for quick budget ways too. Figured I’d note to clarify just in case. Great video.

        I’ve also commented else where about potential spray coating materials to increase performance. What those materials are… am not certain at the moment. However… thinking pike popcorn ceiling… though a more foam material with the highest surface area. Seems the material coating could also have, or have layers with, electric/magnetic/electromagnetic characteristics to improve performance capabilities also for more of a Faraday Cage effect.

  2. “The neighbors really like this.”

    Classic!

    This is really thorough. One of the few videos I think I’m gonna watch all the way through. There’s lots of interesting advice in here, including the reflection-identification at the 25-minute mark.

    One of the problems with acoustic materials, both commercial and DIY, is that you really want them to be fire-retardant. Both for your own safety, and because in some environments, your local fire AHJ might take quite an interest in anything attached to the structure.

    Take a match to a piece of cheap unrated foam, and take a match to a piece of proper fire-retardant foam, and compare the results. It’s dramatic — the unrated stuff goes up like it’s made of flash-paper. The expensive stuff self-extinguishes:

    https://www.youtube.com/watch?v=NEkDLTV0ZHs

    Which room would you rather have an accident happen in?

    1. I haven’t yet watched the video… but I can tell you from experience that rigid fiberglass sheets make great “deadening” sheets and are orders of magnitude more fire resistant than any foam product. Frame the sheet with some 2×2 lumber, wrap with fire-retardant architectural cloth and you have good-looking fire-resistant panels that look good and will last years.

      Also… ain’t nobody going to be making an anechoic chamber in their mom’s basement. Panels won’t make an acoustically poor room into an acoustically good room. The best that can be achieved is to reduce early reflections and resonances. For occasional vocal recording, make a tent out of some quilts and moving blankets.

    2. +Nate B Good point. Tech Ingredients did make and test anechoic panels of polystyrene. I wonder if they are flame retardant? (runs off and googles “polystyrene flame retardant”) Yes, and as a matter of fact, just in the last few years dow and owens corning changed from one toxic type to another less toxic type. Since 1980 apparently, polystyrene insulation has been produced with a flame retardant.

      Fire is just plain toxic. Notice the billowy smoke from the one treated with a fire retardant. Which building would you rather be in? JUST KIDDING I’m not trolling. The idea of fire retardant is to get the fire to self extinguish or at least burn slower till the FD can get there to put it out, not produce healthier smoke. Borrowing from building materials to get cheaper soundproofing is pretty clever — much of it already has fire retardant questions answered. Packaging materials are another story.

        1. “People heal and if you need a new one they are fun to make”

          My guess based on some of the 70’s-80’s lyrics wasn’t so dangerous:
          Golden Earing: “…She sends a cable comin’ in from above
          Don’t need no phone at all
          We’ve got a thing that’s called radar love
          We’ve got a wave in the air, radar love…”

          Def Lepard: “…Livin’ like a lover with a radar phone…”

          Now we get Gwar with Salaminizer lyrics that eludes we need more Anechoic Chamber and Faraday Cage safe shelter areas seems to have fun to make.

  3. There is a parking garage close by and I’m always amazed at the little amount of sound reflected from the wall when I’m walking down there.
    They used bricks with holes, but instead of placing the holes vertically as you would normally do, they are placed to face out of the wall. It’s similar to what you see in this picture, but with bricks that have much smaller holes and of course cemented together: https://commons.wikimedia.org/wiki/File:Tijolos_%3D_Bricks.JPG
    I guess, if you build something like that indoors, you’ll soon have lots of insects living in your room.

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