In theory, one way to make a window that blocks most exterior sound is to take two plates of glass, thoroughly seal the space between them, and pump all the air out. Sound can't travel through a vacuum, so only the edges of the window would transmit sound from the exterior to the interior.
the fly in that ointment is "air pressure". At 14.7 pounds of pressure per square inch or 101.3 kiloPascals, a decent-sized evacuated window will be crushed. Not good.
On another hand, there happens to exist some very interesting stuff known as "aerogel". Sometimes called "solid smoke", at the molecular level it is basically a sponge-like 3-dimensional polymer. Air molecules fit in the sponge, of course; there may be 10-100 times as many air molecules in an aerogel, than there are molecules of the actual substance of the aerogel.
It happens that a chunk of aerogel has a moderate amount of stiffness. I'm sure you can crush it with your bare hand, but not without SOME effort. So how about we fill the space between the window panes with aerogel, before evacuating it?
An aerogel is not perfectly transparent, so this notion will not be useful for a window where you want to see a great view. But the average ordinary window over the back yard will not be hugely affected because we are talking about a fairly thin aerogel here; you can still see things with a bluish tinge, and maybe a little fuzzy.
Now I'm not certain just how much an aerogel can help an evacuated window resist air pressure, but in one respect that's not super-important. See, aerogel all by itself is the second-best sound-insulator known (second only to vacuum)! You might not need to evacuate the window at all! But I'm figuring that a LITTLE evacuation, say to 1/2 ordinary air pressure, would offer the best of both.
I see, after writing this, that there is another Idea here about aerogel and windows. Fortunately, the thrust of that one is different than this one. Also, it is my understanding that aerogel is not very water-resistant (RAIN resistant). So that idea must await further development, while this can be implemented immediately.