This could be caused by any of several reasons; some potential candidates are listed below. The only way to investigate most of them is to open up the television, turn it on, and inspect the interior. This is extremely danerous if you are not familiar with servicing electrical devices. Don't do it if you have no experience, because a shock can be a life-altering experience (i.e., altering a live body into a comatose or dead body). - If the noise is coming from the speakers built into the television, it may becaused by excessive noise in the audio system or 60 cycle hum. Hum is usually caused by poor shielding around the power transformer(s), audio circuits that are located too close to power circuits, and/or inadequate grounding. Hum appears as a 60Hz background noise, with some higher-order harmonics at multiples of 60 (e.g., 120Hz, 180Hz). Higher-pitched random noise from the speakers, higher than the normal 'muted' volume level, may be caused by a fault in the audio circuit. Some components generate more noise when they fail, rather than simply failing outright. - Noise may be produced by mechanical vibration in certain electrical components. If the television power supply uses a standard transformer (e.g., square or rectangular plates with windings on opposite sides), the plates can vibrate and produce noise if the transformer was not assembled properly. Other components and sub-assemblies inside the television may also vibrate, producing noise. Sometimes these can be reduced or eliminated by moving the television slightly, which may bend the case in a slightly different way. - Noise may be produced by any high-voltage components in the television. The most likely candidate is the flourescent light source, if your LCD television uses one to provide illumination. Any transformers or coils used in the power supply to the flourescent light may produce hum and noise. This noise level may drop once the tube has warmed. CRTs (cathode-ray tubes) would sometimes produce a high-pitched buzz from the windings on the tube. While these are not present in an LCD display, any higher-voltage components may still produce noise.

Hmmmmm, ALL TVs i have ever come in contact with do that o.O. I usually hear this humming or buzzing sound the second the TV is pluged into the electricity plug and no one else has been able to hear it apart from me, so even if there is a loud noise or something in the room i will never be able to overhear the TVs buzzing. I have also always asked myself what it is O.O. but i guess it's normal and its the voltage or something