But for police officers already on the job, the policy is not so clear-cut.
After years of informally allowing officers to wear hearing aids, and even paying for some, the department in late 2009 began enforcing a ban on the hearing devices, forcing older officers who had them to retire and instructing younger officers to stop wearing them at work.
Two of those forced to retire have filed a complaint with the federal Equal Employment Opportunity Commission, contending that the policy forbidding hearing aids is discriminatory toward those with hearing loss, according to the officers’ lawyer, Colleen M. Meenan.
The former officers, Daniel Carione, 44, and Jim Phillips, 40, also contend that the policy serves as a deterrent to officers who otherwise might report their hearing loss.
“This just forces the ones with hearing impairments to hide,” said Mr. Carione, a former deputy inspector who received a hearing aid in 2009 that was paid for by the department, only to be forced into retirement two years later.
The two men say that because the department does not routinely test officers for hearing, the hearing-aid ban does little to weed out officers with hearing loss.
One officer, who normally wears a hearing aid but removes it while on duty, said he believed that his hearing deficiency left him less equipped to adequately serve.
“I do everything I can to reduce the odds of getting myself hurt, or someone else hurt,” said the officer, who insisted on anonymity because of his condition. He acknowledged that there were times when he could not properly hear communications on the police radio.
“I had to do a warrant check and I couldn’t hear the words,” he said. “I could hear the sound, but I couldn’t hear the words.”
Paul J. Browne, the department’s chief spokesman, said it was “not actively looking to see if people have hearing aids.”
“But presumably if someone came forward and said, ‘I need a hearing aid,’ and it indicates that your hearing is diminished, then that could lead to a disability retirement,” he added.
The department has not publicized its ban on hearing aids for active officers.
In three cases, the Police Department has told officers to stop wearing their hearing aids even though it had previously authorized their use, Ms. Meenan said.
Mr. Browne said those three cases involved “officers who were under the impression they needed hearing aids, but did not.”
Mr. Browne said hearing aids were incompatible with police work because they were vulnerable to “mechanical failure, earwax buildup or any number of things,” and could not completely compensate for hearing deficiencies that might render an officer unable to hear a command properly.
In challenging the department’s policy, Mr. Carione and Mr. Phillips also raise questions about the extent of job-related hearing loss among police officers, who hear some of the loudest noises the city has to offer, in higher doses than ordinary citizens experience.
Over the years, many police officers who had spent their careers working in the subways complained of hearing loss, said Robert Valentino, a former spokesman for the transit police, which was a separate police force until 1995.
“You work in the subway over time, no matter what, you’ll have hearing loss,” said Mr. Valentino, who said his own hearing declined noticeably between 1968 and 1980, the period when he worked underground. “The noise is just incredible.”
A study about noise in the city’s mass transit system that was published in The American Journal of Public Health in 2009 found that “exposures of a few hours to as little as 2 minutes a day” to the noise levels on some subway platforms “would be expected to cause hearing loss for some people given chronic exposure.”
Mr. Carione’s hearing loss dates to July 4, 1996, he said, when he shot and killed a drunken man who was menacing him with a knife. Another officer fired five shots less than two feet from Mr. Carione’s ear.
Mr. Carione pointed out that in 2004, despite his impairment, he could hear well enough to dive off Canarsie Pier while fishing one night and save a drowning autistic man.
“I heard enough to hear that splash, didn’t I?” Mr. Carione said in a recent interview.
He said he sought a hearing aid about three years ago when he was given command of the Queens division of the Internal Affairs Bureau. His new office, in Queens Plaza, was next to the elevated tracks, and the noise compounded his hearing difficulties.
When Mr. Carione asked for a hearing aid, the Police Department obliged, sending him to an audiologist and paying for the $3,000 device. As a result, Mr. Carione could hear again on his right side, he said. But a few months later, at a follow-up visit, a department surgeon told him the hearing aid could mean the end of his career.
When he later learned that the police pension fund’s medical board would retire him, he recalled, “I wept and I begged them to put me back to work.”
Mr. Carione and Mr. Phillips both have at least 20 years on the job, a term of service after which many police officers retire because they are entitled to a pension at half-pay. Both, however, are asking the Equal Employment Opportunity Commission to seek to have them reinstated. Mr. Carione said he always thought of himself as a “lifer” and had planned to stay in the department until he was 63, the mandatory retirement age.
Mr. Phillips, who was a sergeant in the Bronx, said he began to lose his hearing in October 2008, after he was assigned to police a loud, whistle-blowing protest by hundreds of construction workers.
After complaining of hearing problems, he was fitted in October 2009 with two hearing aids, each with a small clear tube that runs along the outside of his ear. Although he was initially sent back out on the streets with the Bronx Task Force, he was forced to retire in March.
“They told me that a perp can knock your hearing aids out,” said Mr. Phillips, using police slang for a criminal. “But eyeglasses can be knocked off, too. I contend that if you draw your weapon, you’re better off not having hearing aids than not having eyeglasses.”
Thomas Graham, a former deputy chief, wore a hearing aid, and he said he knew of no policy forbidding them during his 37 years on the force.
“If you wanted a hearing aid, as long as it’s not pink and dangling out of your ear, nobody is going to bother you over it.” said Mr. Graham, who retired last year at age 63.
It is unclear exactly what prompted the Police Department’s crackdown on the use of hearing aids. After Mr. Carione was told he would be retired, he lobbied top departmental officials unsuccessfully, trying to persuade them to rethink the policy.
Many officials were briefed on his case, Ms. Meenan said, including the police commissioner, Raymond W. Kelly. Mr. Kelly himself wears hearing aids, but as a member of the department’s civilian leadership, he is exempt from its physical and age-related requirements.