You can hear a slight noise from the TV speakers (only models with TV centre speaker mode).
Models with TV centre speaker mode have a CENTER SPEAKER IN terminal or S-CENTER SPEAKER IN terminal in the back.
If an AV receiver is not connected to the CENTER SPEAKER IN terminal on the TV, or if an audio system that supports the S-CENTER SPEAKER IN terminal is not connected, you may hear a slight noise from the TV speakers when [Speakers] is set to [Audio system].
If you are concerned about the noise, disable the following setting:
Press the HOME button, then select:
[Settings] — [TV centre speaker mode] in [Display & Sound] — [Audio output].