It is not easy to do. Try control and f to do a search on this site for soundproofing and similar words. We have discussed it before.
Declare war, when they are out there, turn on your 78 rpm record player and blast em out with your favorite Slim Whitman record. Also, if you can't beat them, then join them. Sounds like it might be fun in the hot tub at midnight.
And about everyone I know that bought a hot tub and put it outside, used it for a while, after the novelty of it got tired of it and the chlorine, pretty much quit using it, and then finally sold it. That is why i recommend bathtub replacements.