If it is a buzzing or whining sound it is most likely the cooling fan or the color wheel. You should have your TV diagnosed by a technician as one of these parts is likely failing or has failed.
Hope this helps,
Last night I was watching TV and heard a pop. The screen dimmed considerably and there was a loud noise coming from the back. I initially thought it must be the lamp but then I pulled it out and it was still making the noise. It now does not come on.