I’ve worked with audio my whole life, and am a member of the Audio Engineering Society.
I’m not saying this isn’t possible, but it’s difficult to understand how it would be done.
It would have to be very powerful to cause hearing loss, but at high frequencies the signal would be attenuated by the physics of the eardrum, carpet and furniture in the room, and even the air itself, which, being fluid and compressible, is a poor medium for ultrasound.
On the other hand, to make powerful low-frequency sound would require physically big equipment. Maybe you could make a large fake painting into a secret giant woofer, or vibrate an entire apartment wall? The gig would be up as soon as people walked through a doorway and felt the air moving back and forth, or saw papers or small items moving in the room with the speaker.
A very puzzling story.