[sdiy] oscillating a plate

[cris at music-service.nl]

Hi all,
i don't think this is the best forum for this question, but i have to try...
i have a 1,52m long metal plate and i want to bring this plate in 
selfoscillation with sound, this sounds crasy but some people do 
things like that....
I hang this plate vertically and i put a frequency of 60 Hz in the front 
nothing happened. I think you need 1/4 of the wavelengt in frequency 
to make this plate to oscillate, but nothing happened, only my ears 
and my speakers are almost damaged.....
If somebody knows something about this, just some links or 
something like that, please please help me, because i get more and 
more frustrate with this problem....
thanks in advance
cris