Ok, this may be an indication that something else might be wrong then. Is the buzz coming mostly the front (the flat panel screen itself), or is it coming from the back of the panel? If it's the later, then it might be from the transformer/drive circuitry and I seem to recall that some previous Pioneer owners had success in calling a tech that swapped a board and the buzz was reduced.
I have listened to a few 60" Pioneer screens and they all buzzed pretty similar, including my 141FD (except for one 6020 in a store which seemed much louder). With no sound, sitting at about 9' distance, powersave mode "standard" (off) and with bright images on screen (TV menu, PC image, snow...), I can hear it clearly, but I never "noticed" it during a movie. My set is currently at 236 hours and I have not noticed any change in buzz volume.
In my opinion, if you're watching a movie and you start to notice the buzz when you're NOT looking for it, then either you have a set that is defective in some way, or you have very sensitive hearing. To check which one, have you tried to listen to other 151 panels?
I believe no one who hears the buzz has ever found a buzzless Pio. I don't think anyone who says their Pio is "dead silent" has ever reported hearing the buzz on another Pio display. Other plasma brands may be quieter because they have an additional layer of glass which probably reduces the buzz sound but lowers the picture quality a little. What I believe we should expect from these sets is that they do produce a light buzzing sound that can be heard in a silent room, but that sound should not interfere with your viewing. It is a tradeoff for the better picture quality. Looks like currently, no amount of $$$ can buy the "perfect" set.
For new readers who are considering a Pioneer and wondering about the buzz, here is a link to my previous post on the subject: http://www.avsforum.com/avs-vb/showt...6#post15270526