Ours has a button on the far right to adjust chime volume. I assume you have tried that if you have the same option.

This is farout I know, but if it were critical for me to hear it I would put one of my wireless intercoms near the dryer and lock the mike on.
Or a baby minotor.
Or a dog that doesn't like chime/buzzer noises and barks to let you know it (kidding-sorta)
Note: Don't forget to unlock the mike. That can be a scary situation under the wrong circumstances.

Set a timer on your computer like this one: Online Minute Timer (http://timer.onlineclock.net/)

Or get a louder buzzer put in, but we just bought one of those type dryers and they look fairly difficult to get into.