Using audio in a considered approach is a great way to enhance a users experience but you must also be accommodating to users that cannot hear or have hearing problems.
It is something rarely done but a little thought into including these types of demographics will make for a much greater experience.
Museum of Liverpool are one of the few museums that I have come across that have found a way to solve this issue. In addition to the push buttons to begin the audio experiences there are also buttons to show sign language and subtitles on the screen.
It is not intrusive or forced upon for those who do not wish to see subtitles or sign language but always easily available for those who require it.
For exhibits where the audio playback is on a constant loop and non-user started, the screen show subtitles at the bottom of the screen as a “best-of-both-worlds” compromise.
Audio enhancement can bring a great level of detail and immersement for guests but it is always worth considering the other users and how you can also increase their experience.
It needn't be an expensive addition. For example, the user-interaction buttons at the Museum of Liverpool seem to simply trigger a different video for playback on the screen. A task most computer and media playback systems see as trivial.
Check out the Museum of Liverpool - http://www.liverpoolmuseums.org.uk/mol/