Advantages of beryllium?

I read a recent story about the diplomats that were stationed in Cuba and lost their hearing, apparently due to some very high frequency sounds. Apparently those frequencies were generated by metal dome tweeters. The highs break up above what most consider the upper limits of human hearing so they just produced sounds about that frequency and let that " break up " do the rest.
Crazy

Now boys........behave...it is just a hobby.......just go on tweeter and let loose....that has become trendy now..