The bizarre hearing loss experienced by U.S. diplomats in Cuba was likely caused by a covert sonic device, the Associated Press reports. The Americans experienced a sudden and unexplained loss of hearing in fall 2016, leading them to cut their assignments short. Some of the affected Americans have since had to start using hearing aids. An investigation has determined that envoys were exposed to a secret device outside of their residences, but it is still unclear if the technology was intended to be a weapon or to serve some other purpose, U.S. officials said. In reported retaliation, the United States has expelled two Cuban diplomats.