Garmin does not include the audible alert. I have always been a Garmin user so I bought 2-3490's assuming they did. I am returning them and buying 2-Tom Tom's. The Tom Tom do have an audible alert. GARMIN needs to (excuse the pun) get up to speed.
If you change locale to a country in Europe like Belgium, the settings will show up audible alerts option that's hidden normally. Having said so, it will not work with all streets, only few areas. Langauge and voices must be in American-Jill. Goodluck,
Choose which ones to alert for, then back up one and select Audio to set the alert. There is just a single tone though and it alarms only for POI, not speed.
I have owned 3 different models of Garmin. None have audible speed alert related to the speed limit included in the map file. The current speed turns red if greater than the speed limit on newer models. My 255W didn't even do that. There's almost no way to respond to this without coming off as flippant, but does no one look at the instrument panel on the dash of the car? Even a glance once in a while? Should a driver get pulled over for speeding, lack of an audible on the GPS unit is not a valid defense. Most speedometers on cars are 2-3% faster than actual anyway, and that variance increases ever so slightly as the tire tread wears down.