Acoustic neutrality …

The subject:- A small private recording studio’ vocal booth

Small rooms/spaces are notoriously difficult to acoustically treat :  Calculating reverberation time is tricky as Sabine’s formula falls apart at the seams due to small rooms having insufficient reflections to guarantee statistical accuracy, and, the standing wave frequencies are much higher than for larger spaces, dumping the resonance peaks right in the middle the lower vocal region.

However ….

The room:

A small vocal booth, measuring just 2.4 long, 1.1 wide & 2.26 in height, connected by a door and communication’ window to the control room.


Both rooms originally constructed on quite a serious budget, with all available cash going into
construction rather than acoustic treatment. Which is fine, working to a tight budget somethings got to give, and cutting back on acoustic treatment makes sense as it can be retro fitted, where as of course, real construction issues cannot.

After learning that the vocal booth had a “character” which wasn’t really liked or wanted, the owner tried several unsuccessful routes to a cure:
* Engaging an “acoustic designer” on a “hourly/daily” consultation basis.
* 2 or 3 different self treatment scenarios involving various foam panel/tile products.
* And finally, engaging us.

Our service:

As we quite normally do, time after time, we took the rooms physical details from the owner and computer modeled it’s “current” acoustics.
We then modify the room’s surfaces in the model to arrive at a treatment scheme, and ball park “cost implication” for either:
1) Us to design/supply & fit, or, for
2) Us to design & supply just any “special materials” required, along with instructions guides for the owner to complete on a “DIY” basis.
3) Us to just conduct the design stage only.
(Options 2 & 3 obviously reducing costs).

It should be stressed, that at this point of the owner/customer is charged a very nominal fee for our:
A) “before/after” graphical evidence

B)  WAV audio file “before/after” demo.  And,

C) Likely cost implication guide.

The theory being, we think the customer deserves enough information to make an
informed decision. And since we conduct the design, remote (“by wire”) there are no expenses for us to account for, like site visits Etc.

Actual reverberation time plot, supplied at the time: Red trace = before treatment model, Green = treated model (& recommendation), Blue = Measured verification after treatment.

Reverberation time graph.jpg

The job:

With the scheme accepted we arranged a time over the phone, where the owner is in the room with a tape measure, and we are in front of the computer. Another costly site visit is now saved as we verify all detail measurements required to “factory make” a bespoke treatment system.
Finally, the first and only time we see, or need to see the room, is the day we fit the treatment.

The result:

After treatment the owner checks the acoustic with a snippet of sung vocal, and eureka, the
“sound” of the room itself has gone, leaving a pure, accurate, uncolored vocal sound.
Realize, all this happened in under 2 weeks, with minimal upheaval on site, no need for expensive and time consuming site visits, and produced a trustworthy outcome with confidence.
Something which, will virtually never happen with “off the shelf” treatment products or “out of box” treatment kits, as the one vital element missing from these so called solutions, is that of the design element.
Where proven accurate modelling techniques with targeted and properly balanced treatment
(“how much”, “where fitted” & “materials used”), efficiently achieves desired results.

The funny bit:

Amusingly, the customer (being a part time writer/recordist, with a regular job) was at work during the day of the treatment fitting.
When he returned, and although I couldn’t personally hear a massive difference, I was in the middle of tracking down a strange mid frequency overhang that I could definitely hear !.
Just a hand clap was enough to get this weird little “ziiiing” sound going !.  Absolutely sure it wasn’t the room as such, I finally tracked it down to the aluminium door handle, which was merrily ringing away whenever exposed by a sound stopping suddenly.
After a brief discussion, a discrete hole and a squirt of expanding foam in the rouge handle… all was quiet.  !!

Of course, without the room itself being so “well behaved” this issue would never have come to light, and would have always added to the general cacophony of peaky elevated reverberation time, causing the coloration.