Do you have the sound turned on the settings for the game? Most games have music and sound effects volume controls in the settings.
Do you have other sounds? Can you play music in the Music App or can you hear the soundtrack from a video in the Videos App? Do you have keyboard clicks and other system sounds?
Did you check the side switch to see if system sounds are muted or double the home button and swipe to the right at the bottom of the iPad to get to the software switch for system sounds in the task bar?