Good well at least I know now that its a inline fan 
Any idea about the sound ?
Any idea about the sound ?
Most likely pretty loud, they are not really made to be quiet on this types of fan's.
You will more commonly find them used in duct work, and places where noise is not a issue.
They're actually surprisingly quiet and move a lot of air...
http://www.ebay.ca/itm/4-6-8-10-12-Inline-Duct-Fan-Air-Blower-Hydroponic-Grow-/121108274609?pt=LH_DefaultDomain_0&var=&hash=item1c329d9db1
12" moves just over 1200 cfm @ 55dB