How can I have Calendar use an audible alarm for alerts? Today I missed an event alert because I stepped away from my desk for a few minutes. What settings would affect whether Calendar Alerts have an audible alarm?  Is there a way to force an audible alarm sound for specific items?
If you go to Settings -> Notifications, then under In Notification Center, select Calendar and scroll down to Calendar Alerts and choose it.

This will give you the screen to select an alert tone for your calendar alerts. You could select a ringtone for it even. To my knowledge there is no option to select a different tone for specific calendar items.