If old windows were wood or vinyl frame that would account for transferring less noise. Another possible contribution would be if there was more airspace between 1940s and storms. If storms had caulk cord between frame and mounting surface that would lessen noise transfer.

The old windows were wood and yes, there were several inches between the old ones and the storms. The storms were pretty mediocre quality though. So it sounds like we did make a mistake. Besides reinstalling the storms, any ideas on what we can do now?

Sadly the replacement window industry is great at marketing itself, the old windows have no marketing budget. Yes you had a much larger cushion of air between the storms and the window than you do between the two panes of glass now. Hopefully reinstalling the storms over your new windows will help.

"" So it sounds like we did make a mistake."

Todays energy codes require insulated glass (double pane). Many companies do not even offer single pane glass, including ALL vinyl or fiberglass manufacturers.

Interesting - when I replaced my old, wood, single-paned windows and triple-track storms with Andersen 400 double-paned windows I thought there was less noise from outside.

What windows did you install? You might want to check - installing storms over them may void the warranty?

Dennisgli - this gives me hope! We installed LePage wood windows. But like I said above they haven’t done the caulk or trim yet so hopefully once that’s done, it better or at least the same.