I'm not 100% positive these will help you but there are two things that MIGHT help.
In Android Auto there is a setting on your phone called "Play conversation chime" and you could turn that off.
Alternatively if that's not it, then there's a chance that lowering the volume at the moment that the "incoming text noise" is playing will reduce that particular sound.
In Android Auto there is a setting on your phone called "Play conversation chime" and you could turn that off.
Alternatively if that's not it, then there's a chance that lowering the volume at the moment that the "incoming text noise" is playing will reduce that particular sound.