This is a short tutorial on the steps required to turn off the lock sounds and keyboard clicks on iPhone 4S
Step 1: Press the menu button on iPhone 4S then tap the settings icon on the Home Screen.
Step 2: In the Settings screen, tap the Sounds option
Step 3: This should display the following sound options which can be used for configuring iPhone 4S.
Step 4: Turn off the Lock Sounds and Keyboard Clicks by sliding ON/OFF switch available next to the option.
Now your iPhone 4S will not make sounds while locking or using keyboards on the iPhone.