How often have you been in a public place and heard a phone notification ding nearby, and reached for your own pocket, only to find out that it wasn't from your phone? Spare yourself the unnecessary confusion and change your default ringtone and notification tone to something different.
To start, navigate to your phone's Settings app and tap its icon to open it. Next, Tap Sound under the Device heading: Here you can change your phone's ringtone and default notification sound, and toggle various other sound effects on and off.
Tap either the Phone ringtone or Default notification sound headings to change either of those two alert sounds: Pick one from the list—you'll get a preview of whichever alert sound you chose—and once you find the one you like, tap OK. You're done in the Settings app at this point, so go ahead and press the Home button.
The default notification sound you set in the Settings app will apply to all notifications, but if you want a different notification sound for when you receive text messages, you have to change that through your text messaging app.
If you use the default Messaging app, tap its icon to open it, tap the Menu button in the lower right corner (denoted by three dots), then tap Settings. Scroll down to the Notifications section and tap Sound. Select a new notification sound from the list, then tap OK. Once you're done, tap the back-arrow button in the upper left to leave the Settings screen. Other apps may have their notifications sound options in their own settings menus.