IPhone/No Incoming Ring Tone and Text Message Alerts sounds?

Hi there, My iPhone 4s 16gb is running iOS 5.0 and is not jailbroken. Suddenly I don't have sounds for the Incoming Ringtone and Text Message Alerts sounds, such as Unlocked sound, incoming call ringtone and dial pad sounds. I have tried to reset all settings but still I have no sound.

Try these suggestions first: go to settings, then sound, then check to see if All sounds are set to on. If yes then press your volume button up and check to see if your sound is all the way up. If yes the last thing you want to do is check to see if your vibrate switch (on the side of the phone above the volume rocker) is set to vibrate. If you see the orange on the switch it is set to vibrate and will make no noise.

Can you play music through your music app? If not then you may have a defective device and you must call apple or go to an apple store to get a free replacement device.