A recording of the noise that some US diplomats were subjected to during a suspected sonic weapon attack in Cuba has been made public.
The audio, released by the Associated Press, sounds similar to the noise that a mass of crickets might make, but has an electronic basis.
At least 22 US government personnel are “medically confirmed” to have been affected by the attacks, with some suffering permanent hearing loss and traumatic brain injury.
The recordings themselves are not believed to be dangerous to listeners.
The origin of the device thought to have produced the original sounds remains unknown.
Those affected in Havana reported the sounds hit them at extreme volumes, with the attacks causing hearing, cognitive, visual, balance, sleep and other problems.
Victims were targeted in hotels and official residences, not in the US Embassy itself.
The recordings have been sent for analysis to the US Navy, which has advanced capabilities for analysing acoustic signals, and intelligence services.
Cuba has denied any involvement or knowledge of the attacks.
The US has not blamed Havana, but has faulted President Raul Castro’s government for failing to protect American personnel.
White House chief of staff John Kelly said: “We believe that the Cuban government could stop the attacks on our diplomats.”
The recording has been digitally enhanced to increase volume and reduce background noise, but is otherwise unaltered.
It includes pulses of varying lengths and some sustained periods of several minutes or more.
Last month, the US pulled 60% of its staff out of Cuba and urged Americans not to visit the country following the attacks, putting recently improved relations between the two countries at risk.
All non-essential staff and their families at the embassy were ordered to leave, with only “emergency personnel” allowed to remain.