Shape of portable vocal booth matters?

I’m going to construct a simple portable vocal booth shortly, and I figured I could just use a cube-like structure to put the acoustic foam in. But in this video, it mentions (around the 0:25 mark) that such a shape (with 90-degree angles) probably isn’t the best for voiceover work because it’ll create a sound that’s too boxy. So now I’m thinking that I’ll have to devise something totally different from many/most of the various DIY portable vocal booth videos I’ve been seeing on YouTube. Have any of you heard something like that before? If so, what shape is optimal?

DO NOT make a square box. My old office was surgically square and I could clap my hands, go for coffee and when I got back, the clap was still wapping back and forth between the walls.

We had a sound room two building ago whose major feature was non-parallel, non-square walls and ceiling. It had very little soundproofing other than that. Maybe thin industrial carpeting and some acoustic ceiling. I pushed a number of successful recordings through that room.

It doesn’t have to be much. People would go in there for a conference or talk and never pick up on the wacky wall alignment. For some reason it just sounded better and clearer than the other rooms.

Flynwill knows the spells to do that. I’ll ping him.


Thanks for the info. Definitely a new direction I need to take then. Glad I asked before I got started.

I don’t think there were any particular special spells – just keep the walls and ceiling not parallel. The room Koz is referring to was a fairly large room probably 20’x15’ so not sure how much the design is apropos a home recording booth. I would guess that the walls were 10-20 degrees off square, and the ceiling was perhaps 6" lower at one end vs the other. Some effort was made to soundproof the room (as in keep outside sounds out). 3 walls were “double stud” construction (one set of studs support the outside sheet rock, one set supports the inside sheetrock) with fiberglass insulation, the forth wall was against the concrete exterior wall of the building, I don’t remember if we did anything to cover the concrete.

To get ideas about small booth design I’d recommend checking out this company’s gallery:!

You’ll note that many of their small voice-over booths are quite square, but have acoustic treatment on all of the interior surfaces.

Thanks for that. Most of my voiceover work is in a small stand-up space under some stairs with a moving blanket attached to the ceiling and hanging down to form a U shape in the area; while a small portion of the ceiling is parallel to the floor, part of it is slanted and not parallel to either the floor or the opposite wall. I wanted to create a portable vocal booth to cut down even more on the “white noise” room sound (and also to use on the go if I needed to). I’m guessing that the shape of a plastic bin (which is not a perfect square or rectangle shape) would be preferable to a cube-style box?

Something like this?

Or maybe just construct something in a V shape (with an angled top) out of light material such as cardboard or coroplast?

This is how I did it. The pictures are too big for in-line presentation. You have to click.

The ropes on the ends are to connect the walls to each other. Each wall is double moving blanket. I can turn any room into a studio in about 40 minutes.

Here it is on a voice shoot for a movie sound track.

I couldn’t do the ceiling, but note I soundproofed the floor. Kill off any reflective opposing surfaces.

That wacky thing on the right is my home-built vibration isolator with a rock-band microphone in it.

All parts either from the hardware store, or the US Postal Service (except the microphone).

No glue. Natural stresses keep everything together.


The main problem with “box” type portable booths is that they invariably sound “boxy”. There are thousands of articles on the Internet that say how easy it is to make a portable acoustic booth by putting the mic in a box and stuffing it with fluff, and go on to say how great it works, but in my experience that is just not true.

Even the best sound absorbent materials work only on a limited range of audio frequencies, and are never totally absorbent in any frequency range. Placing sound absorbent materials directly in contact with reflective materials (the box) reduces their effectiveness substantially, and any kind of rigid box will have resonant frequencies according to its size and shape.

Other types of acoustic shields are available that do work. They still won’t give good results in a room with terrible acoustics, but they can make a substantial improvement in a room with “reasonable but not great” acoustics. When used in conjunction with some heavy blankets, they can provide pretty good results in most quiet spaces, but they can’t do miracles - a bathroom will still sound like a bathroom.

Here’s an example of the type of acoustic shield that actually works and does not add significant amounts of colouration to the recorded sound:

The construction differs substantially from the box full of fluff in several ways:

  1. The outer skin is substantially “open” so that it does not bounce sound back into the mic
  2. Multi-layer construction to absorb a wide range of frequencies
  3. Combination of absorbers and diffusers to minimize sound reflections
  4. Highly quality materials greatly out-perform cheaper alternatives (and better durability).
  5. Carefully calculated proportions, thickness and spaces to “trap” lower frequencies.
  6. Sufficient distance from the mic to allow the mic to “breath”. Studio microphones are either open at the back, or “ported” to allow the diaphragm to move freely in response to the sound. Overly restricting the space around a microphone, even with sound absorbing materials, can produce detrimental changes to the microphone’s frequency response.

Placing sound absorbent materials directly in contact with reflective materials (the box) reduces their effectiveness substantially

That’s why the semi-standalone booth works so well. Separated from the room’s walls, reflected sound has to go through four layers of moving blanket. Two going out and two coming back.

The Se unit looks like a very good deal, but you should also remember that the microphone, given a gentle cardioid directional pattern, is aimed at you…and the wall behind you.

When used in conjunction with some heavy blankets

What he said.


I had purchased a SE-RFX face shield for around $139.00 and it works great. 6 days later, I saw a Woman that spent $27.00 for a piece of Acoustic Foam. She tied a string to the top and bottom, making about a 300 degree circle, with her Snowball mic sitting in the center. She sounds like she is sitting in a million dollar studio. :astonished:

If the room already has pretty good acoustics, that may be all that is necessary (and it’s likely to be a lot better than a box stuffed with fluff).
I used to record in a small bedroom. It was carpeted and had fairly heavy curtains and a spare mattress stood up against one wall. My microphone was “shock mounted” on a sturdy floor stand. The acoustics were pretty good with no additional acoustic treatment. One of the plus points of this room was that it was an irregular shape, which helped to reduce room resonance.

I would want to hear the room without the $27.

With the microphone on the desk, I guarantee they had no noise coming up from the apartment below. Do you have a sound clip? If not, you only have their word on it.

My “studio” is soundproofed, but if you’re not paying attention, you would miss it.

Acoustics is not black magic, but it’s seriously dark gray.


Somehow I missed all these posts - now I need to go back and read all this good information. I know I’ll have more questions about various other things, since I’m still learning, so thank you in advance for your help and patience.

OK. Back in front of a real keyboard. There are simple ways of eliminating noises coming up from the desk or floor below. There’s the towel and book method.

And the spider method.

That’s a home-built one. You don’t have to do that. That’s me being obsessive.

And that’s just the stuff coming up through the floor.

You can eliminate slap and odd comb effects (wine glass voice) by putting thick padding on the desk. That blue thing under the book and towel is a moving blanket.

Then you put a moving blanket or several regular blankets or a large, full bookcase behind you.

Then you use that horseshoe thing or the semi-round of sound-proofing material around the microphone. No, you can’t use packing foam. Packing foam is designed to take up space and not be dense. That’s the precise opposite of the requirement.


I don’t really have a problem with desk vibration (mic’s not on a desk), vibration from the floor below (I record in the basement), or even with reverb. The room has a carpeted floor and I have a moving blanket hanging from the ceiling. I figured all I’d need would be just a little extra help to tone down the white noise room silence. Just today I found out about something called the Kaotica Eyeball; looks intriguing, but I’m not about to shell out $200 for a piece of foam. I like the circular-shaped $27 fix with the Blue Yeti sitting in the middle - something like that would probably work perfectly - but shouldn’t it have something on top too?

We had someone on the forum that used one of those. In the end they got rid of it because it coloured the sound (made the mic sound like it was inside a football).

White noise is likely to be more from the mic and pre-amp than from the room.
I know that ACX refer to “room tone” to refer to the background noise of a recording in a quiet room, but really they are just describing the “noise floor” of the recording and are trying to do so in a way that suggests that it is better to have a “little” noise in the background than to have dead silence. dead silence is unnerving and does not occur on Earth, other than in a few acoustic research centres (Experience: I've been to the quietest place on Earth | Life and style | The Guardian).

A short recording in WAV format would help us to know what we are dealing with. A simple, totally unprocessed recording, of you counting “…1…2…3…4…” The dots are pauses. How to post and audio sample to the forum:

That’s the other reason I doubt the $27 solution works just like a studio. That’s a Blue Yeti USB microphone famous for producing low volume, slightly hissy work.

Another variation on the test clip:


OK, I just recorded a sample - I hope I did it right. The mic I use is an Audio-Technica ATR-2100USB plugged into a Scarlett Solo. I do have the gain knob on the Solo turned all the way up because it’s a dynamic mic. But perhaps that’s too high. I played with the gain a few times (before I even came to this forum for suggestions/assistance) and when I put it in the middle it seemed very low (of course, this was before I understood how to run the compressor and then normalize, which boosts the volume quite a bit).

The good news is your voice is perfect and clear and the background sound (room tone) is undetectable.

The not so great news is the voice volume is super low. Audacity has sound meters and time line graphics (blue waves) to aid you in setting voice volume.

This is roughly what your Audacity is supposed to look like during a normal recording.

The knobs and adjustments on your sound devices should be wherever they need to be to make the Audacity sound meters do that. I understand many modern systems force you to work with low volume because Too Low is preferable to Too High. Too Low can be an inconvenience. Too High can destroy your show.

Too Low is not without its own problems. The Scarlett Solo has its own noise. That’s a gentle ffffffffff sound I call “rain in the trees.” This is frequently lumped in with Room Tone. It’s not the same. Room Tone you can fix by unplugging the refrigerator (as one of our posters does). You’re stuck with ffffffff.

It’s possible to record so low a volume that your voice and the Scarlett noise are too close together. That’s what happened in your posting.

See Attached. I boosted your voice to normal performance volume and the ffffff noise also boosted. Turn your speaker or headphone volume up in the first three seconds of the clip. That ffffff noise will not pass ACX standards. It’s too loud.

Yes, it is possible to fix that in post production with Noise Reduction, but you are warned against accumulating a laundry list of patches and fixes that you have to apply to each and every chapter of each and every book. Much better to make a clean recording right at the top and see how few corrections you have to make.

As a test, and because we keep telling people you can do this, I made a voice recording in my third bedroom that passed ACX tecnical standards by just making it a little louder. No patching

Also, waiting in the wings is an ACX failure they call Too Much Processing. If you mess with the sound enough, you cause other sound damage and ACX has been known to bounce submissions because of that. This is the same problem as medicine side-effects. Aspirin will eventually start eating holes in your stomach.


See how close you can get to the ideal blue waves and bouncing sound meter. Another thing I like to do as a practicing obsessive is see, as a test only, if I can overload the microphone. I turn everything up and speak louder and louder as I watch the Audacity sound meters. As a fuzzy rule, it should be possible to overload Audacity (bouncing meters turn red and the blue waves fill up) without screaming into the microphone from a half-inch away.


In case I wasn’t clear, it’s not a bad idea to watch the Audacity sound meters out the corner of your eye while you perform. That’s why we changed the sound meters to be much larger than earlier versions and designed a color scheme that starts getting angry (yellow, orange and then red) as you approach overload.

I’m not making that up. That’s what the sound engineer would be doing in a studio.

You are the sound engineer.


Exactly. I cleaned up the noise in my first recording session with Noise Reduction (and used compression and normalization) and it sounded decent to me (it also passed the ACX Check tool and ACX’s initial checkpoint when I uploaded the first 15 minutes). But after the second session, I had trouble recreating that decent sound (of course it’s entirely possible that what I thought was decent isn’t really all that decent). I want to make the recording clean from the start so I don’t have to tinker with the audio too much. I don’t think I can boost my microphone recording volume any higher than it already is - as far as I know that’s as high as it goes (in my original file). Today I purchased an Audio-Technica AT2035. If that gets here in time, I’ll switch over to that and just start the book all over again. It’s a small book that should be under 2 or 3 hours and I have until the last day of February to get it in but I want to be done much sooner than that.

I just remembered that in my first recording session the computer with the Solo was outside the small room I was sitting in. For the second recording session (as well as the test one I did tonight for upload here), it was inside with me … so that’s probably why the ffffff sound is so much more pronounced. Do you think if I moved the computer far out of the room that this would eliminate the problem entirely? What if I hooked the Scarlett up through an external USB hub before connecting it to the computer? Would that help too?