This clip from a feature produced by Alex Jones, Austin, Texas videographer, shows military sound weapons mounted on NYPD trucks. This was filmed during the Republican National Convention in NYC August, 2004. In this instance they were used for crowd control.
A variety of interest groups use similar weapons testing them on unpopular persons in this country. Psychologists, police and FBI informants, organized crime families all use these devices to harass their targets. In some areas for profit corporations run illegal businesses with police protection harassing persons for personal, political and economic purposes.