Peter,

Tuck Andress uses a surplus hearing test booth to record his wife Patty right in their own home in San Francisco.

They have made whole albums like that, with her singing in the test booth and Tuck playing his guitar outside the booth. One can also place the guitar amp inside the booth with mic to overdub in effective isolation, as well.

Here's a bit of quick basic info on how to measure the ambient noise levels in your closet space.

http://www.ehow.com/list_7628211_specifications-audiometric-booths.html

A Sound Level Meter can be purchased from Radio Shack.

Fifty bucks, someone in your business should have one anyway and you might have one of the good older original models, still a workhorse within the industry.

http://www.radioshack.com/product/index.jsp?productId=12680845

Find out where you stand empirically as regards background noise before purchasing anything in the way of panels.

Depending on what your background noise survey tells you, the situation could be done any number of ways, for example, if the area already has chiefly a low background noise level to begin with, the type of panels to incorporate would have to do mostly with the actual acoustic in your booth rather than having to deal with both the acoustics plus ambient noise abatement.


--Mac