On Aug 1, 4:38*pm, "Bob M." wrote:
"windcrest" wrote in message
news:49c5075e-d1ce-4302-8530-

That all depends on one's tolerance level. *I have a house full of
musicians living here (me, kids, wife, and my oldest ones band)...
Try recording sound with a furnace runing, you would be very surprised
at how easily it finds its way onto the recording, microphones are
very sensitive. *I'll never get it to 0db but nonetheless the ductwork
is usually the biggest source for transmitting the fan noise.

Do you have physical shock mounts for the mics? *Best to start there.

http://www.heilsound.com/pro/products/shock.php

Of course. The noise is in the air, the air sound alone is picked up,
the additional duct sound is aded on top of that. Shock mounts for
mics keep the mics themselves isolated from their stand and the floor
vibration, they do nothing for actual noise in the air.