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).