1. From the home screen, swipe down from the Notification bar.
   
2. Tap the Settings icon.
   
3. Under the 'Sound' tab, tap Default notification sound.
   
4. Select the desired sound, then tap OK.
   
5. Messaging alert settings can be changed from within the Messaging app.
   Note: From the home screen, tap the Messaging icon > Menu icon > Settings > Notification settings