I agree that the panel buzz is variable. I think if you can hear it with TV volume set to about 10-15 sitting about 10 feet away, it is abnormal.
In my case, the buzzing appeared, was quite bad, then slowly over several hours and days of viewing, it decreased to a much less notable level. I think this happens to be a common defect that is difficult to quantify, unlike a dead pixel or other defects. Since it is difficult to objectively measure the intensity of buzzing, many people are left to wonder if perhaps they are just being too anal.
I think I have a guess to determine which panels are defective in buzzing. If powermode save 2 significantly reduces buzz volume (from very loud to hardly there), then it is defective, if it reduces buzz but not by much, then this is the normal amount of buzzing.