Is it the volume or the TPMS alert settings that have the problem? Sounds more like the low pressure point needs adjustment, or more importantly that the RV tire pressure needs to be increased.
To determine, weigh the rig and get the right pressure for that weight from the tire company and make sure the TPMS system is set for the correct pressures.
The problem with lowering the volume is that if there truly is a tire pressure issue - you won't hear it. And that defeats this important safety device.
2002 Newmar Mountain Aire Limited 4370 w/ Spartan K2 and Cummins 500hp
ASE Master Certified (a long.....time ago...)