Subject: How can you break glass by simply singing?

I have seen T.V. shows where people break glass by simply singing so high 
it breaks the glass. However I believe it is when the people sing at the 
glass's natural resonation level is when the glass breaks. Please stop be 
if I am wrong. Well is it possible for me to construct a device i.e: A 
parbolic dish that emmits these resonation frequencies and crack/break the 
glass? Any links or any info, books would be greatly appreciated. I have 
looked through a lot of search engines and your archives but the only 
thing I found close to this was the saser. Thank You onces again. And the 
quicker the response the better please I have approximately 2 month before 
my science project is due.

Re: How can you break glass by simply singing?