Personally, I don't think it's proper to approach a couple of people who have a history of loud noise. At least, not when they're making that loud noise.
It is possible to approach them, next time you see them mowing lawn etc. and mention, "hey, Joe? Some nights I can hear you two yelling. Is everything ok?" and if Joe gets bristly, you could say "Well, sorry you guys aren't getting along all that well, but I'd appreciate it if you could keep it down at night, since we're early risers and work an early shift. Oh and hey, have you seen the Green Bay Packers this year?"
So, if you do this, give it at least one more chance. One more "rawr rawr noise..oh we need to shush....library voice" is ok. If it's going "RAWR RAWR BLARGEL YELL HOLLER YOU @#$#$%$#" then call the cops as a noise complaint.
It's the cops job to figure out what's happening, if the noise complaint is actually a DV in progress, or even a robbery in progress....just because it gets dispatched as X does not mean the activity is X.
And you could get earplugs, just sayin'.