You Should Know

Why YSK: Because if you are planning to attend a protest, you might want to be prepared for the possibility that these technologies are used against you.

I know, this sounds like some conspiracy nutjob's imagination, but it's real. Here are some wikipedia links:

Directed-energy weapon

A directed-energy weapon (DEW) is a ranged weapon that damages its target with highly focused energy without a solid projectile, including lasers, microwaves, particle beams, and sound beams. Potential applications of this technology include weapons that target personnel, missiles, vehicles, and optical devices.

Examples of such weapons include:

Long-range acoustic device

A long-range acoustic device (LRAD), acoustic hailing device (AHD) or sound cannon is a specialized loudspeaker that produces sound at high power for communicating at a distance. It has been used as a method of crowd control, which has caused permanent hearing damage, having an extremely high decibel capacity (up to 160 dB measured at one meter from the device). Other uses have included for negotiations in siege situations; to deal with piracy at sea; for mass notification during natural disasters or other emergencies; and by defense forces, including several navies.

The Washington, D.C. Metropolitan Police Department used a LRAD at the January 21, 2017 Women's March. Protesters at the June 1, 2020 Washington, D.C. George Floyd protests said police gave little or no warning before employing aggressive tactics against them. A 2015 settlement requires federal police to give large crowds several loud dispersal orders before deploying chemical irritants and other dispersion tools. Using an LRAD to issue loud protest dispersal orders would have complied with the 2015 settlement requirement. In September 2020, it was revealed that federal officials had explored the use of the device and the Active Denial System ("heat ray") to disperse civilians protesting outside the White House in June of that year, but had been advised that the National Guard was not currently in possession of either device.

LRAD was reportedly used by the Oakland Police Department during the clearance of the Occupy Oakland encampment on the morning of 25 October 2011. Police in San Diego, California, used an LRAD on May 27, 2016, to order anti-Trump protesters to disperse.

Active Denial System

The Active Denial System (ADS) is a directed-energy weapon developed by the U.S. military, designed for area denial, perimeter security and crowd control. Informally, the weapon is also called the heat ray since it works by heating the surface of targets, such as the skin of targeted human beings.

The ADS was deployed in 2010 with the United States military in the Afghanistan War, but was withdrawn without seeing combat.

In 2014, there were reports that Russia and China were developing their own versions of the Active Denial System.