The US Navy is working on a non-lethal weapon that would render a person unable to communicate.

The handheld Acoustic Hailing And Disruption (AHAD) system records a subject's voice with a long-range microphone then amplifies it and plays it back on two distinct tracks, one nearly simultaneous with the original and another on a slight delay, perhaps a few hundred milliseconds.

Using a parametric speaker, it directs the sound back at the person speaking, with the resulting echo theoretically disorienting the person and impeding their attempts to continue talking.

'Due to the delayed auditory feedback effect, the target speaker's concentration will be disrupted, making it difficult for them to continue speaking,' according to the weapon's patent application, approved in early August.

The chatter would be inaudible to anyone else, New Scientist reports, 'so, as far as any bystanders can tell, the target will seem to have trouble speaking for no obvious reason.'

The AHAD patent was granted to Christopher Brown, an engineer at the Naval Surface Warfare Center near Bloomington, Indiana.

It's not clear if the device has been constructed or tested, though the Navy filed the patent in 2019.

Researchers at Japan's National Institute of Advanced Industrial Science and Technology in Tokyo tested a similar device, called a 'SpeechJammer,' in 2012, saying it was useful for 'controlling discussions.'