A US Navy sailor uses a long-range acoustic device in a drill David Wa/Alamy
The US Navy has developed a non-lethal device that can be used to secretly render someone unable to talk.
This device is called a handheld audio hailing and disruption system (AHAD). It records the speech of the target and plays it back to them after a small delay. Anyone who has ever had their voice echoed back to them on an internet or phone call will be familiar with the disruptive effects of delayed auditory feedback.
