Quoted from sohchx:Went through the menu and adjusted the background volume, didn't help at all. The background volume isn't the issue, the sound effect volume is. Even with the main volume turned down to 2 the plunge sound is still entirely to loud.
There is an old service bulletin regarding sound volume levels, mainly relating to home use volume. I'd start by checking which resistor values are installed in your machine. You don't know what might have been altered, done right or wrong, by a previous owner.
http://mirror2.ipdb.org/files/4505/Stern_2001_Monopoly_Service_Bulletin_133.pdf