....stuff deleted

I tried both string & foam without luck. I still got a constant pitch
howl
that became louder with speed. Then a banged a bar while carrying it &
realized that it's ring was the same pitch as the howl. It was a bell &
that was it's resonant frequency. So I filled the bars with sand. They
are
heavy, but the noise is gone.


You probably don't need to fill the entire bar. I'd probably try caulking
the ends first and see if that works. Jam some paper in about 3-4 inches and
fill the end of the bar with caulk. Over the years, I've lost end caps and
rather than replace them, this worked pretty nicely (and there is always
extra caulk around).

If the noise persists, I would think that the bar/mount attachment isn't
tight enough. It it is, there should be no vibration along the length of the
bar (hence, no noise).

Rick