The beep tones on my Garmin Edge 830 are extremely quiet with turn-by-turn instructions.Unfortunately you can adjust the volume.I hope Garmin implements the function to adjust the beep tone volume.
Agreed the volume is pathetic. Obviously G have never tested the device in a real world situation; wind in your ears, cars rumbling by etc etc.
The same goes for the bike alarm. Your bike will not be stolen because the thief laughs himself to death at the beep.