Turning Lg900g on vibrate?? HELP?

Either my phone is messed up, or I'm plain stupid. I can't seem to get it to go on vibrate for texts and calls..like when I don't want to hear a tone..I've tried the side button..nope just volume changes..tried the actual vibrate button on the keypad..hell no, that turns it to silent!! am I stupid or can someone help me?