In article lgate.org,
says...

This sounds very much like you have misunderstood the sales patter.
Would this be a sandwich of two panes with a IMM plastic safety bonding
layer?

I think that the OP has discussed noise reduction with the sales person
at some time.

A sealed unit composed of different glass thicknesses on either side of
the air gap is a common method of noise reduction.

See:-

http://www.pilkington.com/Asia+and+A...English/Buildi
ng+Products/Householder/SmartGlass+Solutions/Reduced+Noise/Reduced+Noise+
Facts+and+Figures.htm

Sorry about the long link - Tiny URL does not work for this page.

--
Ziggur

"S'ils te mordent, mords-les"