The use of firearms to repel the pirates represents something of a failure for the LRAD system, manufactured by American Technology Corporation (ATCO), a San Diego-based company, because one of the key selling points of the sonic cannon is to obviate the need for violence. Two months ago, an LRAD was used to disperse protesters outside the G-20 Summit -- the first time it had ever been used on civilians in the U.S.

In September, American Technology spokesperson Robert Putnam told DailyFinance that heavy-duty ear-phones could render the weapon less effective. It's unclear if the pirates wore them -- or just don't care about their hearing.

This isn't the first time the LRAD hasn't worked as hoped, though this incident had a much better outcome than a previous episode in which the sonic cannon failed. That time, in November 2008, "The pirates fired rocket-propelled grenades and AK-47s at the weapon; the guards jumped off of the ship, and into the Gulf of Aden," Wired.com reported.

"It now seems that the failure of the company's LRADs was a major factor in its seeming inability to prevent the capture of the ship. It is now openly being asked whether or not they are up to the job," wrote Lloyd's List, the influential shipping journal. Anti Piracy Maritime Security Solutions principal Nick Davis told Lloyd's List that "the pirates were basically laughing at our guys while shooting them out. LRADs don't work when they take an AK-47 round through them."

The LRAD's top volume is 150 decibels. Lloyd's pointed out that "1970s rock shows by the likes of Motörhead and the Ramones regularly subjected their tender young ears to blasts measured at around 148 dB for those at the front of the gig, and thoroughly enjoyed it."