Audio as a weapon

I would like to deviate a bit from the normal audio equipment conversation and delve into the phenomenon of the recent audio "weapon" that appears to have been deployed in Cuba upon State Department employees and now, it appears, in China. I know that very low frequency can be dreadful to listen to but anyone out there have any ideas with regard to how audio could be used as a weapon? It is not my intention to draw speculation of a political nature, I am only interested in the technical aspect of audio as a "weapon". Anyone have any thoughts?