Calendar alerts vibrate but. No noise
I've had this problem on my iphone 5 from day 1. Sat on the phone with Apple for over an hour & didn't solve the problem so they sent me a new phone coz mine was only a few days old & guess what..... It's still doesn't work. It's something I used all the time with my previous iPhones with no problems so I've had to start using the reminders app. Can't understand what the issue is & why it's still not sorted even after all the updates.
Make sure the basics are covered:
1. Settings-Notifications Scroll down to "Calendar Alerts" and then select the Alert Tone you want to use OR
2. Settings-Sounds Scroll down to "Calendar Alerts" and then select the Alert Tone you want to use.
3. Check the "Do Not Disturbed" times. Settings-Notifications-Do Not Disturb.
4. Settings-Notifications-Calendar and make sure that the "Alerts" feature is enabled under the "Alert Style" option.