A bystander who suffered permanent hearing loss after Pittsburgh police deployed a Long Range Acoustic Device (LRAD) against protestors during the 2009 G-20 Summit has filed a federal lawsuit against the city. The device emits pain-inducing sounds to disperse crowds and is also deployed on American warships.

Karen Piper, then a visiting professor at Carnegie Mellon University, tried to observe the G-20 protests in Pittsburgh as research for her book on globalization.

The G-20 represents the leaders of the world's most powerful economies and the group's summits attract a large crowds of anti-globalisation activists and others opposed to what they see as an undemocratic group promoting harmful free market policies.

While Piper was trying to leave the protest, without warning the police activated a LRAD a short distance away from her. She immediately became nauseous and dizzy, and felt fluid flowing from her ear.

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