wauww - 10 years, and problem has not been solved.
I was searching for a solution to this exact same problem, january-2022, and saw this forum-question (written 10 years before, in 2012!).
What is happening? Are Garmin not using their own stand-alone navigation units?
Because, it is an obvious "challenge", that one cannot hear the "warning signal" ... and as another customer has written, this can lead to speeding-tickets ... simply because of "Overlooking gentle low-volume" Warnings.
As a contrast and forepicture, the TomTom Go's have a LOUD alert-signal, tthat DRAWS IMMEDIATE ATTENTION, in time for us as drivers, to check / lower our speed!!!
Dear Garmin: 10 years. Why?
This is the Express forum. Please contact Product Support to discuss this issue as speed camera warnings are normally loud enough.