Federal Signal Corporation has denied the allegations Charles Mostoller/Reuters

Claiming that the blaring noise produced by sirens on fire trucks has permanently damaged their hearing ability, thousands of firefighters in the US are suing an Illinois-based company called Federal Signal Corporation. The siren maker has, however, denied the allegations.

More than 4,000 former and current firefighters accused the company of not doing enough to ensure those on fire trucks are safe from the noise of the sirens. The firefighters want the noise from the sirens deflected from areas where firefighters position themselves, but the company, said that deflecting the noise would have a negative impact on road safety.

Federal Signal Corporation has also called on firefighters to wear ear protection gear as recommended by fire departments throughout the country. "There's a constant ringing in the background. There's not really anything you can do for it. It's a real annoyance. I just try to have the TV higher than the ringing," chairman of a committee of retired Chicago firefighters, George Beary, 72, was quoted as saying by the Chicago Tribune.

"Clearly, you don't have to have sound going all the way to the rear of the fire engine. If you're driving behind a fire engine and you don't see a 50-foot-long, red engine with lights going on and off, there's really something wrong," Beary told the Associated Press.

"Firefighters have testified that they want a loud siren that projects noise to the front and sides of fire trucks," said David Duffy, attorney for Federal Signal and added, "Accidents often involve vehicles that hit fire trucks from behind, necessitating a loud noise in all directions."

The exposure faced by the firefighters is "intermittent but intense". Rick Neitzel, who studies noise and other exposures at the University of Michigan School of Public Health, said: "A lot of the questions now are: Is the current recommended level appropriate for exposure that a firefighter would have? And I would say we're not entirely sure."

Marc Bern, the attorney representing the firefighters, said that lawsuits against the company surfaced more than a decade ago. Firefighters have filed cases against the company in places such as New York, Philadelphia, Boston, New Jersey and Chicago. In 2011, the company paid $3.6m (£2.42m) to settle cases of more than 1,000 firefighters in Philadelphia.