Basically, checking off the two mute buttons for BGM/SFX in the options does not actually mute it, instead it merely makes it very, very faint, but still hearable.
Additionally, some things within the option menu don't make sense at first glance, such as "hap Control Guide", and "Identification".
I can only assume the latter basically allows whether or not a player can view my info, but the former makes no sense to me at all.