Liquid crystal display televisions like those LG Electronics manufactures may come in different styles and formats, but ultimately the technology is similar regardless of the make or model. A whistling noise is a sign that something is faulty inside of the unit. Troubleshooting some common issues may pinpoint the problem and help you determine if your television needs repair or replacement.
There may be a problem with the speakers or audio processing on the television. A quick way to test this theory is to mute or lower the volume. A noise related directly to the speaker or audio system will disappear when you turn the sound off. If you continue to hear the whistling noise once you turn down the volume, you can rule out the audio as the source. If the noise is gone, then you will need to take the TV in for service. A technician can test the board that controls the audio processing and examine the speakers for defects.
LCD televisions have a cooling fan to help prevent the system from overheating. The television requires a lot of energy, which produces heat. Like a computer, these systems have an interior fan that helps dissipate the heat and reduce incidents of overheating. If the blade is loose, sticking or broken, it may be noisy when active. The fan will run at intervals, so if the whistling sound is intermittent, the fan is probably the culprit. To check this, unplug the set and remove the back to look inside the TV. The fan will be to one side. You can try tightening the screws that hold the fan in place. If the connections seem secure, check to see if the blade is loose or broken.
A more serious possibility is that one or more of the capacitors on the circuit board of your LG LCD TV is leaking or faulty. When capacitors fail, the tops pop and they leak. A faulty capacitor may produce a noise that sounds like a buzz or a high-pitched whistle. There may be other performance problems with the TV, as well; the set may keep shutting off or the picture may flicker. If you rule out the audio and fan as causes, then the capacitors are probably to blame. When you take the back off of the TV to check the fan, you can look at the capacitors at the same time. They look like tubes or batteries attached to the circuit board. It is easy to spot a bad capacitor, as the top will tent upward; this is a sign that the TV needs service.
A new LCD TV from LG should not make a whistling noise; the sound is a symptom of a problem. If your television is still under warranty, do not take the back off or try to fix it yourself. This may void your service contract. Call LG to determine how to exchange or repair the set. If the TV comes out of the box making that noise, return to the store for a replacement.