Re: "silence chamber" (nested enclosures)

["jpbeale" jpbeale]

Posted by: "Eric Benjamin"
> Commercially available sound booths usually give about 40 dB of 
> attenuation in the mid-band (500Hz)...

If performance is critical, and you have the space and the money, then
you can built a second larger isolation booth entirely enclosing the
first booth. To enter you would pass through two separate doors. That
would double the attenuation from 40 dB to 80 dB, which is enough
attenuation to push the large majority of background noises completely
below the threshold of hearing.