Are you having no sound when typing problem on your iPhone 4S / Iphone? In my case, the no sound when typing a message issue on iPhone suddenly occurs and I have no idea why it happens. Tried checking on Settings but all sounds alert are turned on, after several times of exploring the iPhone 4 iOS5 unit I manage to found the solution about the issue. I will post how I solve this no sound problem on iPhone 4s, or you may also refer to this post if you are having the same problems with you iPhone or iPad.
Enable Sounds When Typing in iPhone
1. Check your Loud/Silent switch located on left side of you iPhone above + and - button (see image above). Switching the button on will display a bell icon on your iPhone screen. Try typing hope the sound is now back.
2. Restart your iPhone by holding the power button and home button together for 10 seconds. After restarting check if the sound and other alerts are now working.
3. Go to Settings and check if all the alerts you want to enable are on. If it is turned off try to tap the On button. After turning on check if it solves your problem.
You may also read this post about IPhone 4 Auto Rotate Not Working With Circle Icon On Top Screen for your reference.
Steps above are the basic troubleshooting when your iPhone/iPad is sound when typing is not working.