For years kits were available for focused sound wave weapons basically the frequencies are in the higher ranges that are above the threshold of pain rather than just irritation (check a basic physics text for this common graph). This is function of both amplitude and frequency. Possible consider ear protection as part of basic protestor survival kit? Not sure what type is adequate.

The techology is described at the American Technologies website at:
http://www.atcsd.com/tl_hss.html

although other focused sonic weapons are likely available.

Breaking News and Commentary from Citizens for Legitimate Government
July 10, 2004
http://www.legitgov.org/
All links to articles as summarized below are available here:
http://legitgov.org/index.html#breaking_news

Sonic Weapons to be Deployed at Political Conventions? Master Blaster: A New Weapon for Homeland Security --American Technology Corporation has designed a Long Range Acoustic Device—a megaphone with unprecedented clarity and aim that can shoot compact sound waves across several hundred yards at up to 150 decibels. Miami, Los Angeles, the Port Authority of New York and New Jersey, and the Department of Homeland Security are considering purchases. With protesters coming to New York and Boston for the conventions, might we see the first domestic use this summer? American Technology's Carl Gruenler hints: "All I can say is there are cities you would recognize."


Informant: hydratwo