I’ve recently started experimenting with a new microphone, a Lawson L47MP condenser mic I purchased some time ago. Among the differences I’ve noticed, compared to the Electrovoice RE-27 N/D dynamic mic that’s been my mainstay since 1992, is the Lawson condenser’s much greater sensitivity to ambient room noise.
My home office and recording studio share the same space, a large recreation room re-purposed and reconfigured for the business. On the other side of the long interior wall is the gas forced-air furnace, which doubles as the blower for central AC during the summer months. As you might imagine, between the HVAC noise in the next room and the constant whirring of fans and disk drives of the several computers in the room, noise control can be a challenge.
Acoustic foam on that interior wall and a few other places, carpeting on the floor, soft tiles on the ceiling, and special multi-layer insulating shades on the windows have all helped to mitigate the room noise, but have not eliminated it completely.
I entertained the thought of purchasing a Gretch-Ken sound isolation booth but eventually decided against it. Its footprint would take up too much valuable office space, and I couldn’t justify the expense, given the type of production work that is my bread-and-butter.
Reading a back issue of Radio and Production Magazine recently, I noticed a post by someone who’d built a makeshift sound booth, using a PVC pipe framework, mover’s blankets, and acoustic foam. It wasn’t pretty, but it seemed to do the job for him.
This led to an online search, which ultimately took me to Harlan Hogan’s article on how he came to build his own portable voiceover booth or “Porta-Booth.” He wrote:
[E]ven a very quiet room – and this applies to homes and apartments, too — can sound like a “big, boomy box” to your microphone, instead of the tight sound booth quality we are used to in purpose-built studios. That’s because in addition to picking up the sound of your voice directly, the microphone also “hears” the ambient sound of the entire space.
Until last year, I’d build myself a tiny little fort out of every pillow and comforter I could scrounge from housekeeping when on the road, even though my wife found my constructions less than pleasing esthetically. Then I remembered the brilliant idea of audio and video guru, Douglas Spotted Eagle, that Jeffrey P. Fisher and I described in our book, A Voice Actors Guide to Home Recording.
Douglas realized that for a microphone to sound good and tight you didn’t need to be inside a sound box – only the microphone did. So, he built a simple two foot by two foot five-sided box out of foam core, lined it with acoustic foam (often available 24″ X 24″ tiles), stuck his microphone inside, and spoke and sang into it.
Dubbed the VO Box, the results were amazing. The sound of the recorded voice was warm, full, and resonant no matter what room it was in.
So I decided to construct a road warrior’s version a.k.a. The Harlan Hogan “Porta-Booth”
The more I read, the more I realized that this small iso-booth, built to accommodate only the microphone and not the performer, might be the ideal solution to my problem.
In his excellent article, Mr. Hogan provides instructions for the DIYer who’d like to build his own version of the Porta-Booth. Since I already had some 2′ x 2′ squares of pyramidal acoustic foam, all I needed was a Whitmor Collapsible Cube. A quick visit to WalMart’s website led to the purchase of a two-pack in coffee-brown, on sale for $13 or so, delivered free to our local store.
It took me literally just a couple minutes this evening to cut the necessary three pieces of foam, using an electric carving knife I picked up at Goodwill many years ago specifically for cutting and shaping sheets of acoustic foam. (It’s by far the quickest and neatest way to cut this material.)
Here’s the result…
Right away I ran into a glitch: the L47MP stands 18.5″ tall fully extended. I had to reposition it on the mic stand, bending it down as you see on the left in order to fit it into the 12″ enclosure, so I could still side-address the mic. (I can’t imagine how this in any way would compromise the function of the capsule, but I just might call Gene Lawson to double-check and be on the safe side. Can you tell I’m not an engineer?)
The only other adjustment I had to make was to come up with some sort of platform on which to rest the enclosure, to bring the mic up to a comfortable height for reading. Two 12″ x 12″ acoustic foam bass traps nested together formed a perfect base, providing the additional benefit of isolating vibrations that might emanate from the hard desktop surface.
So far, so good.
I know that many radio station production rooms suffer from similar noise pollution problems, whether it’s bleed-through from adjacent studios, sales office conversations, people talking in the hallway, whatever. So, I wanted to share this nifty and inexpensive solution with you.
One other radio application: for salespeople who record clients at their place of business, carrying one of these might be just the ticket for improving the quality of those on-location recordings. That’s what I’m going to do with the other Whitmor Collapsible Cube and sheet of acoustic foam I have on-hand—make a second Porta-Booth to carry in my vehicle.
Thanks to Harlan Hogan for coming up with this inventive solution for taming room noise when recording voiceovers.