How about subsonic sound? Travels very well.
Sound below the range of hearing is not as directional and does not carry the energy I need in my application. I understand it has some effect on nerves by creating tension and a sense of fear. It seems to me that it has been used in theaters and haunted houses to create a hair-standing-on-edge sensation. That’s not what is happening at the embassies where staff has suffered brain damage. That sounds like microwaves. The Russians used to beam microwaves at embassy windows because glass acts like a speaker and you can convert the microwaves back into audible sound to hear what is said in the room. I thought all embassies were equipped with microwave sensors for that reason. But, apparently not.