Plasma's buzz/humm?

Not all, but some do. Like mine does usually, depending how you run it or what it's displaying. This model is known as having a propensity for it. If it was running the way they set them up in stores, I imagine the buzz would be quite "loud", whereas I can hardly hear it and probably mostly do because I listen for it. Certainly can't hear it when any sound is turned on, which I guess is the way most people use their displays...

I don't think I've ever heard a plasma in the 42-46" size buzz though, it tends to be the larger ones IME. Also the ones with thinner glass tend to do it more IME, but I don't know if that's a fact or coincidence. A web search should tell if the buzz is "normal" for your model or is an anomaly of the example. If the buzz on a store display bothers you a lot, I'd completely stay away from that model. In my case, I knew about it in advance, and obviously decided I could live with it (which is surprising, because I'm usually picky about stuff like that). Another thing is my buzz is MUCH less in the summer (especially during this "heatwave") compared to during the winter months, something I haven't quite got an explanation for except to say somehow humidity might affect it...so that means if a buzz on a model you're looking at is "loud" now, I'm suggesting it might get louder in the winter.

Many of the older CRTs and some newer plasmas seem to buzz as they are "stressed". For example as an all-white screen comes up, or something else really bright.

I have a Watt Meter and you can see the Watts rise on those sorts of scenes on Plasmas and CRTs. (LCDs are not affected in the same way). This would seem to indicate that the buzz relates to more stress on the power supply, or perhaps other electronics. For example, on my Panasonic plasma, the Wattage used for an all-black screen is almost 1/10th the usage for all white, with most programming about 1/2 way.

With TVs, the power consumption can be brought down with a proper optimization which may help to minimize buzz, while also providing better picture quality.

http://www.digitalhome.ca/forum/showthread.php?t=76161

You can tell if this is the case by switching away from the default picture mode to something more "appropriate" like cinema or custom, or similar, or by reducing contrast somewhat.

^ Yes, the volume definitely depends on the amount of "stress" on the power supplies. For instance, I use an "energy saving" mode largely because the buzz is very noticeably less. (Besides the proper viewing mode/calibration.) Frankly, I couldn't see any PQ diff in that mode, keep meaning to go back and compare now that the TV is older and I'm more used to it... And "energy saving" mode with a largish plasma is very relative. Likewise the buzz is almost absent when the display is black.

But what I was getting at was many plasmas of similar screen size use roughly the same amount of power. Some buzz to an extent depending on what's displayed, and some don't at all, ever. It seemed to be the more expensive thin-glassed ones that did it more, and that's what led to my hypothesis: We know that if we take a small vibrating source, and couple it to a large thinnish "unsupported" diaphragm, the vibration source will be largely amplified. Like in a speaker. So that's what I guessed might be happening with some displays: the PSs' vibration is getting amplified by the thin glass = (poor) construction method. PSs and glass could have been isolated better. I think it's a possible explanation, or at least a major contributing factor...

Edit: My Pio 151 manual says buzzing is "appropriate for plasma technology". Of course that's nonsense, it's not "appropriate" at all.