mail.app sounds quit working

Mail.app sounds require the Audio Midi Settings to be set at 2ch - 32bit Float for the sounds to work. The Audio Midi Settings always go back to 2ch - 24bit Integer when the Mac is rebooted. Sounds come back after the Audio Midi Settings are reset to 2ch - 32bit Float.

How can I fix it so the Audio Midi Settings don't change back to 2ch-24bit Integer thereby breaking mail.app sounds?