Hi CraigV,
If you are having issues with the sound on your DU7200 TV, please try the following steps:
1) Set Sound Output to the TV Speaker by going to Settings > All Settings> Sound > Sound Output.
2) Ensure you are running the latest Firmware. Go to Settings> Support> Software Update.
3) Run a cold boot. To do so, hold down the Power button on the Samsung TV remote until the TV turns off and then on again. This should take about 5 seconds.
If you continue to have issues, please reach out to us so we can further troubleshoot or schedule warranty service. Thanks for being a Samsung customer!
To contact us, please call us at 1-800-SAMSUNG, 8 AM - 12 AM EST, seven days a week.
~Samsung Advisor