How can I reduce the amount of noise transferred through my exterior walls?
There are soundproofing curtains and soundproofing panels that can be found through an internet search for soundproofing curtains. 

They are not cheap, window curtains starting in the $300 range for an average size window (and yours are much larger). Panels start at about $200 for a 4x8 foot unit and they still need to be hung on some sort of frame. Preframed versions are a good bit more.

Many people swear by white noise machines, but not all people find them effective.