Sorry to hear you are having this issue. Are you using a home theater or just the TV speakers for audio?
I own a samsung smart TV model UN55F6350AFXZA. It is 3 months old. Turn TV on and begin to watch a HD station (I have AT&T Uverse as cable provider). After about 5-10 minutes I loss the audio, video is fine. I shut the TV off, turn it back on but I now have a non-hd channel on, no problems with the audio or video, works great until I swith it to a HD station then after several minutes I loss the audio again. My cable provider changed the cable box and HDMI cable and still experience the same issue. Anyone experience the same thing, if so how was it resolved. HELP!!