Hi Dave,
To turn off the sound on your Samsung TV, Please know that many buttons on your remote have multiple functions. For example, the Volume button is moved UP/DOWN to adjust volume, and to MUTE the sound, you need to PRESS it in. Pressing it a second time will unmute.
If you are looking to use external speakers, it will depend on how you connect your device. Head to Settings>Sound>Sound Output and select the appropriate speaker.
If you need more assistance, please feel free to contact us at 1-800-SAMSUNG, 8 AM - 12 AM EST, seven days a week. Our LiveChat agents are also available by clicking on the ‘Support’ link on our website.
~ Samsung Advisor