If you’re in a place where your phone sounds may disturb others, you can quickly silence your phone from the Home screen.
Press and hold the Power/Lock Key until the Phone options
menu appears.
Touch Silent mode.
OR
Press the down Volume Key on the side of the phone until all sounds are
turned off.
You can also use these keys to quickly turn
the phone sounds back on. Press and hold the Power/Lock
Key , then touch
Silent mode to toggle between on and off. While in Silent mode, unlock
the screen, then press the up Volume Key once to activate Vibration
mode and twice to turn on phone sounds (continue pressing to increase
volume).