Thanks for your question!
Inspect your device for any physical or water damage that may be causing this then check your audio settings to make sure they have not changed.
If that does not work you may want to try resetting your device. You can find instructions on page 11 here http://bit.ly/VRGG7Z
. Be sure you backup any data you don't wish to lose prior to resetting.
If you need additional assistance or information, please just write us again on this forum or you can also try calling Samsung Customer Support at our toll free number 1-888-987-4357 between the hours 7:00 a.m. to 9:00 p.m. Monday through Friday, and 9:00 a.m. to 6:00 p.m. Saturday, CST. From there, a representative can assist you further!
You can also chat live with a support agent by following the link below and clicking on Mobile Phones under Live Chat Support, or feel free to ask us on Twitter @SamsungSupport for speedy responses in the U.S.
Chat Support: http://goo.gl/ZALJm
Thanks and have a great day!