In article ,
Remco wrote:
Most of my annoyances are in the low frequency spectrum. How many dB's
will this be reduced? And what is this insulation in real-life? (I'm not
a sound engineer). Any ways I can improve it any more?

I measured a reduction of 13dB (wideband) with sliding secondary glazing
spaced about 9" away from single glazed steel framed windows. This in
'subjective' units more than halves the noise, and is well worth it.

--
*If at first you don't succeed, destroy all evidence that you tried *

Dave Plowman London SW 12
RIP Acorn