In both cases, people experienced symptoms resembling types of "traumatic brain injury," according to multiple sources. 01:27Can sound really cause brain injury? Experts whom CNN spoke to described how sounds could be weaponized, but none of them is known to cause the symptoms seen in Cuba and China. In addition, a majority of the patients reported problems with memory, concentration, balance, eyesight, hearing, sleeping or headaches that lasted more than three months. Some of the patients' symptoms are not typically seen in a concussion, such as pain and ringing in only one ear, the study noted.

Source: CNN May 23, 2018 16:41 UTC