For my old Tom Tom there was a voices called Silent Voice which would allow all other sounds but disable the directions.
I use my GPS daily and know the route, the directions are unnecessary, but for the traffic to function I need a destination.
Just use the Garmin programe and record nothing in each field required.
In doing this you get a hiss every time the device wants to give directions.
To fix this crop the sound to a small flat spot on the recording and bingo you are done.
Save to the device and you get visual directions without the annoying voices.
Garmin no voice
