Ceiling Exhaust Fan -How loud is .5 sones?

From the HGTV website: One sone is about equal to a refrigerator running, while four is equivalent to normal conversation.

OK, I'm risking your wrath because what I am going to suggest is not rated in sones....but, FanTech inline exhaust fans allow you to locate the fan itself far from the listening room, so that you don't hear the fan motor at all. You only hear the air moving through the grate. In my BR with the 100 cfm fan on full, you can hear the air quite easily through the 6" grate. At half speed it is totally silent. I'd guess that an oversized grate would make it quieter, perhaps even silent, at the highest setting. Unfortunately on their site FanTech doesn't list sound ratings, because they say that there are no testing standards for remote mounted fans.

Panasonic has a very nice poop fan extractor rated at 3 sones and then they have the very same fan listed as a retro model thats 4 sones. Depends how and on what material the same fan is mounted. Yours for only 399,95. The same fan will have a different sound in a different room depending on size and material build out. Tom

Thanks Aby,
Since I wanted to avoid ANY unwanted sound in my HT room, the design that you mentioned (relocate the fan futher away) was first on my drawing board. But if .5 sones is an exeptional number, then I can live with it. Problem is, what is .5 sones equivalent to realife example?
This is what you are talking: http://www.youtube.com/watch?v=B-qWg60xFtY

Forget Sones those are all WAY to loud - sound like jet engines. You need something with DbA of around 10 at one meter (a big very slow moving fan if you want to move a lot of air). You can hear about 15 to 30 db below the noise floor and this means you will hear any and I mean any bathroom type evacuation fan.

You will need to go custom, IMHO.

Here is a Calculator

Here's some info....

http://www.sengpielaudio.com/calculatorSonephon.htm

I run a whisper fan that is rated at about 30db,too lound. So I have reduced the fan speed in half and sitting 4ft away i can barely hear it.

If I read the graphs right .5 sone = 30 phons which in db level would be about 30db. I think you need to put a potentionmeter on this fan and reduce the speed in half.