SIGINT

A document entitled “Bioeffects of Selected Nonlethal Weapons“ was recently declassified by the US Army in response to a FOIA request by Donald Friedman for information relating to “… the microwave hearing effect, the Frey effect, artificial telepathy and any device/weapon which uses and or causes such effect”. The document returned is part of a 1998 National Ground Intelligence Center study on nonlethal weapons technology the rest of which has not yet been declassified. It discusses in broad terms the effects of microwave radiation,  laser light and sound on the human body and their potential for use in nonlethal weapons. 

Microwave heating is discussed, citing a study conducted on Rhesus monkeys at 225MHz. The report dismisses microwave heating as being of limited suitability due to the long ramp up time to have an effect on the target (15-30 minutes). Contrast this with the Active Denial System that works at 95GHz and heats up the water molecules in the skin much more rapidly.

Microwave hearing is covered next discussing how the effect had been known for some time and indicating that the mechanism is probably due to pulsed RF frequencies causing thermoelastic expansion of the brain region around the cochlea. It goes on to discuss that it is quite possible to cause a voice to be heard in the skull due to this effect referencing a Walter Reed Army Institute of Research experiment which was able to send the words one to ten using this technique. The report suggests it as a possible way of communicating with hostages that their captors would not be able to detect.

The next technique discussed is disruption of motor control using a very fast pulse (nanasecond) at around the brain alpha frequency (15Hz). This causes disruption of the corticospinal pathways leading to muscle weakness, intense muscle spasms and loss of consciousness depending on the exact frequency. Also discussed is the effect of intense levels of sound (140-155dB) which cabn be used to cause spasmodic motion of the eyes and nausea. Finally the report covers the effects of exposure to high intensity laser radiation.

In all the report shows that considerable work has been done to understand the potential of electromagnetic radiation as a nonlethal weapon however no mention is made as to the deployment of these techniques in real weapons.