When muted, either through the remote, or through a button on the TV itself, your Samsung TV should go completely silent. Problems with the TV failing to mute, sticking on mute or only lowering the volume slightly could come from the device itself, the remote control or other attached hardware.
Many Samsung TV models have an internal mute setting. This setting permanently mutes the volume on the TV itself so you can listen to the audio through an external sound system. If the internal mute sets to "On," you will not hear sound through the TV. Your TV could have errors within the motherboard, a piece of hardware that essentially tells your TV what to do by sending actions to different components, such as the speakers. Your TV could also have faulty internal speakers.
If you use a remote control to mute your TV, the problem could stem from the remote and not the TV itself. Old batteries can cause the remote to malfunction. Even newly installed batteries can be faulty and not work right. Beyond the batteries, the TV must receive transmissions from the remote and your remote must be synced to the TV itself. Third party remotes may have sync issues and will need to be re-calibrated.
If you use other devices with your TV, such as a DVD player or surround sound system, those devices can conflict with the TV itself, causing the mute feature to work incorrectly. For example, if you mute while watching a DVD, the remote may only mute the DVD player and not the TV. Check your remote and device manuals for specific instructions.
Repairs and Warranties
Samsung may offer a limited warranty for your TV as well as a refund period. If the mute feature fails to work within the return time frame given, you can send the set back. If the mute feature stops working past the return deadline, you may qualify for the warranty. Samsung also offers service repairs for a fee. You can schedule a repair or read about any warranties that come with your specific device on the Samsung Service Request website.