On Thu, 21 Apr 2005 22:19:11 GMT, "Hi Ho Silver"
wrote:

The rush of return air flow through my plenum cover and air filter is very
noisy and I am wondering if the builder left out some noise reduction
feature. This is not 'mechanical' noise, but the 'wind rush' noise.
The return filter opening is at floor level and the air makes an
upward turn to enter the fan suction which is about 30-33 inches
above the floor inside the return plenum. The filter size is 20"x25". The
actual entrance to the fan is smaller, looks to be about 18"x18" (perhaps
that hole is too small?). There is nothing between the filter and the fan
suction; should there be some kind of 'noise reduction baffle' in that
location? Any hints appreciated. Thanks,

step 1) take the filter out of the return filter opening
and see if that makes a difference.

step 2) with the filter in place, prop open the return air
grill. see if that makes a difference. Is the return air
grill of the "stamped face" variety, or is it of the "bar
type" variety.

Builder model homes typically have cheap, stamped face
supply and return air grills. These impose too great of a
restriction on the air flow. Change them out to commercial
grade bar type supply & return grills, and your air noise
problems may go away.