There are several reasons why you cannot hear sound on your iPad 2. Here are most common reasons why people cannot hear some applications, but they can listen to a TV show, movie, music or a podcast: 
- There seem to be certain apps, or combination of apps, that disable sound. Try doing a system re-set. Press the Home button and the on-off button on top of the iPad at the same time and hold until you see the Apple logo appear. DISREGARD any interim screens that appear, including the welcome screen, and just wait until the apple logo appears. This will “re-set” the iPad, but no data or settings will be lost. This should restore sound.
- You may be able to hear audio playback, such as music, podcasts, movies, and TV shows but NOT notifications, sound effects and some apps. The SIDE SWITCH might be set to SILENT. The solution is to un-mute the SIDE SWITCH button.
- It may happen that you do not get sound even after moving the SIDE SWITCH button that is because in the mean time you have the SLIDE SWITCH set to control rotation lock. To turn it back to being SOUND control again go to Settings, to General > Use Side Switch to, then tap Mute. After you have done this, open the app you wish to play and switch SLIDE SWITCH to un-mute.
In case you ran into difficulties with sound on your iPad, you might have read the following suggestions in Apple’s iPad 2 Manual:
