To turn the phone sounds off
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.Tap Silent mode
.OR
Press the down Volume Key
on the side of the phone until all sounds are turned off.
NOTE
You can also use these keys to quickly turn the phone sounds back on. Press and hold the Power/Lock Key 
, then tap 
and 
. While in Silent mode, press the up Volume Key once to activate Vibration mode and twice to turn on phone sounds (continue pressing to increase volume).