mellowsouls wrote:do any of you fine folk have experience or knowledge of glass
Yes, 30 years working for a leading glass manufacturer, starting out in R&D and becoming Global Product Manager along the way. This was all in the Automotive side of the business but I do know a bit about Building Products as well as glass in general.
When it comes to sound transmission glass is pretty poor. As well as letting sound through monolithic glass (single sheet) also suffers from having a coincident dip which is dependant upon thickness. For 6mm glass (the common thickness in a lot of windows) that's at about 2kHz which is bang slap in the middle of the voice intelligibility range (and also the range for wind and diesel combustion noise in the Automotive realm). Having a double glazed unit improves things, increasing the gap improves it more as does filling the gap with a dense gas. A lot of sealed units would use Argon for thermal benefits but this won’t do anything for the acoustic performance.
If you use two different thicknesses of glass you improve things by having different coincident dips. If one of those glasses is a laminate (two thin sheets of glass sandwiched together with a plastic interlayer, typically Polyvinyl butyral or PVB for short) then you get further improvement. Acoustic laminates use a special interlayer where the PVB sheet itself is a tri-layer with a softer inner core.
Design and installation of the sealed unit, I imagine, would have a big impact. I’m afraid that I can’t help you there but if you want to design a new vehicle with a complexed shaped, high tech, glass – then I’m your man.