How to Take the iPhone 4 Off Vibrate
Vibrate does more than just offer a discrete notification of incoming calls. It also alerts you when a ringer cannot be heard, such as in a concert or noisy club. To address both concerns, the iPhone 4 lets you use vibrate while the phone is in silent or ring mode. This option is enabled by default, but you can turn vibrate off through the phone settings.
Tap "Settings" from the home screen on your iPhone 4.
Tap "On" next to the "Vibrate" field of the "Ring" section to turn off vibrate mode when the ringer is on. Although, this seems counter-intuitive, the "On" listing shows its current status, so tapping it turns it to the "Off" status.
Tap "On" next to the "Vibrate" field of the "Silent" section to turn off vibrate mode when the iPhone is set to silent mode. If you already see "Off" displayed, you do not need to tap it.