interior storm windows for sound insulation?
I live close to the "L" (elevated train) in Chicago and I'm considering interior storm windows with laminated glass to help dissipate the noise coming from the passing L trains 100 feet from my home.
Specifically, the ones I'm considering are made by Mon-Ray and they can fit 1/4" thick laminated glass. However, based on the "impact noise" coming from the passing trains, one contractor recommended 1/2" laminated glass instead which would require a different, thicker, window all together. The other contractor disagreed. He believed that the 1/2" would result in a net loss due to the loss of airspace between the existing window and the interior storm window. The 1/2" would require a different frame all together. I have pretty deep window sills (6.5"), but obviously, but I want to spare an inch or so for shades so they're still within the window opening for aesthetic reasons.
So, who's right here? I want to get this right the first time since these windows will set me back a nice chunk of change.