Are you using headphones or speakers? Does this only happen in FFXIV? Do you have an integrated sound card or a real one? Are you running any programs in the background? Has this always been a problem for you, or did it just start happening?

You should provide us with a lot more information if you want help in diagnosing the problem. Refer to the following thread for a template:

http://forum.square-enix.com/ffxiv/t...hnical-Support!

Also, open your FFXIV config utility, go to SYSTEM, then use the copy to clipboard button to post that information here.