my mio audio is very quiet?

As you couldn’t be bothered to add the model number if you follow these instructions from the user manual for Moov M410/m610 Series my guess is all models are the same with volume control.
If you already know how this is done then explain clearer that there is a sound fault and the buttons aren’t responding.


instructions.
from the map options screen tap the speaker symbol. The volume buttons will appear on the map screen in translucent mode that means fairly light and see through.
Hard cheese if wrong one you should have put the model.

BB
September 2011