Acoustical treatment to minimize exterior noises?

ATS is now building custom plugs for windows….

OH, yeah, acoustic treatment such as sold by GIK and others is not what you need.  Here's an example of noise blocking for windows:

There are in fact acoustical covers for windows and they are IMHO very expensive, around $700 per average window

@whart 

Great suggestions. Thank you

Never knew tone arms had compressors. 

You may find more results in researching soundproofing rather than acoustic treatment. I have soundproofed for a couple situations. One was a large walk in closet where I kept the compressor for my tone arm (plus a whole lotta records that were mostly 2nd tier). I sound proofed the room using mass loaded vinyl (like lead and almost as heavy but it’s plastic). Covered that with an acoustic blanket or two and dead quiet- but, even the small cable pass-through (the size of a duplex outlet) had to be soundproofed. (For that I used Melamine a/k/a Magic Eraser- yes, before it was used as a "magic" cleaning material, including for phono styli, it was designed for soundproofing).

When I moved, I decided the compressor would go into a custom made sound proof box. I found an online facility that had a ready to use product- it was large 2 x 4 ft sheets of melamine with a layer of mass loaded vinyl in the middle. The box was designed by me, build by some local carpenters and lined with those specialty melamine/mass loaded vinyl "sheets." The sheets aren’t cheap but could be used for windows or for other custom applications. That stuff works. The acoustic blankets, alone, were insufficient in my first application.

Here’s what the box looks like:

And here’s a site that sells such material, although not the one I dealt with. You will see that they offer a variety of soundproofing materials. This may not be what you are after, but this could help you get started in your research:

Move.

Just some interesting reading.  I don't have the expertise to comment.  Cheers.