The same as speedcameras. Uncheck all speedcameras, check Your own pois and change 100, 500 or 1000 .wav files to voice. Better or worse, but it works.
I have .wav files for each of my pois, how can I activate them so that a specific wav files plays for a specific poi. For example, when nearing a tunnel it will say "tunnel in 1km" and so on