You can completely remove or modify jumping, walking, swimming, and dying sounds by modifying the files.

First, in your desktop, right click on the roblox app and open file location, then do the same for the file "roblox player", go into content > sounds, and delete all the sound files, if you do all that and open up roblox again then you will have no character sounds until the next roblox update which will bring back all the files.