Chase, a good solution to try is get a baby monitor, the kind that will have a loudness guage feature. Plug it in and whenever you're speaking, keeping an eye on the monitor every so often will register just how loudly you may be, seeing that, you can be encouraged to go lower, seeing the guage not going up like before...doing so, might set you up to start a habit of speaking more softly. This is only just a suggestion-- 
Now, unless you're in the can and there's no toilet tissue available....welllllll, that's a different story! 
~RR
