LRAD Corp., manufacturer of a sonic device deployed against protestors during the 2009 G-20 Summit, has disputed the claims made in an American Civil Liberties Union lawsuit.

Last week, a bystander who suffered permanent hearing loss after Pittsburgh police deployed a Long Range Acoustic Device (LRAD) against protestors during the G-20 Summit filed a federal lawsuit against the city. It was the first time the sound cannon had been used publicly. The device emits loud sounds to disperse crowds and is also deployed on American warships.

She is being represented by the the American Civil Liberties Union.

"LRAD is not a weapon," LRAD spokesman Robert Putnam told the Associated Press. "It is an effective long range communications system used to clearly broadcast critical information, instructions and warnings."

LRAD Corp. is not a defendant in the lawsuit.

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.

"The intensity of being hit at close range by a high-pitched sound blast designed to deter pirate boats and terrorists at least a quarter mile away is indescribable," said Piper, now an English professor at the University of Missouri. "The sound vibrates through you and causes pain throughout your body, not only in the ears. I thought I might die. It is shocking that the LRAD device is being promoted for use on American citizens and the general public."

Putnam said the professor was not close enough to the sonic device to suffer any physical harm, claiming the noise she was exposed to would have been less than sounds created by emergency sirens.

"The LRAD company's self-serving claims that the device could not have caused pain and hearing loss will be news to Professor Piper and her doctors," said Witold Walczak, legal director of the ACLU of Pennsylvania.

Watch brief video of the LRAD being used during the G-20 protest below:

(Warning: Loud.)