Thanks, Roman. In my case, I'm fairly certain it's not the environment. For over 3 years, my Panny TH-50PX50U sat exactly where the 151/141 is today. The Panny was/is completely silent.
Lam, I do have hardwood floors. However, I also have a huge wool rug that runs from the base of the entertainment center/plasma all the way to my sitting area. There are two windows (with curtains) on the right wall; while, the left wall is essentially bare with a couple hanging paintings. The key is, I could not hear any buzzing from my panny, with the exact same set-up and conditions.
I'm still running the break-in DVD. Therefore, I have not tried it with normal content. However, if my 141 is buzzing a little louder than my 151 did with the break-in DVD, then there's no reason to expect it to behave any differently than my 151 did with normal content.
And, yes, I noticed the buzzing on my previous 151 during scenes with low sound effects and/or low dialogue. This is even over the other ambient noises in my room (a/c vents on the floor, cooling fans from my two Middle Atlantic racks located below the plasma, fan from the refrigerator located about 20 ft behind my sitting area, etc...).
No worries. I'm not giving up yet!