Martin:

If you really want to accurately test sound, and/ or accurately record sound you will need to build a "quiet room". See this for an idea of what I mean: http://www.tweakheadz.com/home_studio_construction.htm [this guy's idea about building a quiet room in a closet is a bit kooky, but not half bad.]

Remember sounds in a room combine to make noise louder. See this n00bish guide to sound for a refresher on adding logs: http://www.epd.gov.hk/epd/noise_educ...1/intro_5.html

If you have never seen a real quiet room, it's hard to describe in words, but I'll try. First you can think about the inside of a professional recording studio, where the musicians sit. Such a room will usually have black foam rubber sound insulation that looks like 1/2 of an egg-carton covering the walls. This is good for noise reduction, but is not really quiet. To get really quiet you need to do what stereo speaker manufacturers build to test sound and noise, which is a room covered with foam insulation in the shape of 16 inch isosceles triangles, with the triangles varied in orientation. To do it right you also have to cover the floor and the ceiling as well, and you therefore have to create a suspended "floor" made of chicken wire that allows you stand above the foam insulation. I have been in one of these rooms and it's freakin' QUIET in there. You have never heard quiet, until you go into a room like that, it is actually unsettling, if you stay in there long enough without making any sound you can start to hear the air pressure on your ear drums.

This is not a very good description of what a quiet room looks like, but maybe somebody who works in one of these places can give you some pictures, or better yet, a tour.

Keep up the good work, your posts are truly legendary.