In iPad 2 you can quickly turn off the sound by the following ways
Using Volume Control
iPad 2 has the volume control at the side of the device and one can increase and decrease volume using this control. But you can also use this volume control to quickly turn off the sound in iPad 2. This can be done by pressing and holding the reduce volume control. The following sound icon with no volume would appear on the iPad screen.
Using Side Switch
iPad Side Switch can also be used to quickly mute the sound in iPad. But to use the side switch for mute you need to enable this using the general settings. This can be done by navigating to General Settings and then to Use Side Switch to section and then by selecting Mute option.