Many pilots and controllers are affected by hearing loss, as is the general public. Hearing loss may arise from many causes. Some causes are treatable, while many are permanent and/or progressive. Fortunately for pilots/controllers, the FAA has very liberal hearing standards for all classes of certification. For those not meeting standards, waivers or a Statement of Demonstrated Ability (SODA) are relatively easy to obtain if the pilot/controller is functional in the aviation environment.
Noise Induced Hearing Loss Risks
The most common cause of occupational hearing loss is caused by repeated exposures to noise. Over ten million Americans have noise induced hearing loss and twice that many work in a hazardous noise environment. The Occupational Health and Safety Administration (OSHA) defines hazardous noise on a time weighted scale. Chronic exposure to noise above 85 decibels eight hours a day increases the risk of hearing loss. Louder exposures for shorter periods may have the same effect. Even a single exposure to a very loud noise may cause some permanent effects. OSHA mandates that hearing protection be worn in hazardous noise environments and that employees be trained in the proper use of protective equipment if the noise can not be eliminated. Monitoring of at-risk employees hearing is also required.
Noise in Aviation
Most pilots are at least incidentally exposed to loud noises, even if they fly an aircraft with a very quiet interior. Pre-flighting aircraft on the tarmac or sitting in aircraft with a cabin door open may cause over exposure to hazardous noise. The May 4, 1999 issue of USA Today features a lead article and several others about hearing loss and noise levels in commercial aircraft. Most aviators have plenty of hours in lighter aircraft without significant noise protection. Many aviators also have hobbies or activities that expose them to noise (mowing the lawn, motorboats, power tools, snow mobiles, etc.) As a general rule of thumb, if you need to raise your voice to converse at six feet, you are in a hazardous noise environment.
Protection from noise usually is offered by ear plugs and ear muffs. The foam ear plugs are very effective in reducing noise. Well fitting ear muffs also reduce noise. Together, they offer increased protection, but the effect is not linear. Pilots may preserve their hearing by using protective devices when on the tarmac or anytime they have to raise their voice to communicate. Many headsets used in cockpits offer a great deal of noise reduction passively, such as the David Clark products. Ear pieces are discrete in appearance but offer almost no protection. For smaller aircraft with less noise shielding in the cockpit or with engines closer to the cockpit, the Active Noise Reduction (ANR) headsets may offer a greater degree of protection that conventional headsets.
Noise Induced Hearing Loss Symptoms
The anatomy of the ear serves as a very efficient amplification system. The efficiency of the system is measured by several tests, the most common being the audiogram. The audiogram measures the hearing threshold in decibels (dB) at different frequencies measured in Hertz (Hz). When noise induced hearing loss (NIHL) occurs, the microscopic hair cells in the cochlea of the ear begin to lose function. The first frequencies to drop off are near 4000 Hz. Next, the surrounding frequencies of 3000 Hz and 6000 Hz are affected. This change is very subtle. It may manifest as decreased discrimination, or the ability to understand spoken words clearly, particularly in a noisy environment.
The classic examples include a man watching TV not being able to hear his spouse speak behind him or difficulty understanding a higher pitched woman?s voice at a cocktail party with many surrounding conversations and music. Because background noise in a quiet environment is reduced, many people with hearing loss may note a background noise or hissing (like listening to a seashell or soft static), particularly when sleeping. This is sound perception is called tinnitus. These changes are frequently permanent and may be progressive if hearing is not protected.
Fortunately for pilots, as their noise exposure increases with their hours of flight time, they become more skilled and familiar with radio communications and subtle aircraft sounds. Although their hearing may not be as acute as younger pilots, their knowledge of expected standard radio transmissions allows them to function very well in the cockpit. This is one basis for a FAA SODA for those with marked hearing loss.
Another cause of hearing loss is otosclerosis. Otosclerosis involves a stiffening of the eardrum (tympanic membrane) and the three tiny bones responsible for amplifying sound pressure waves, the "hammer, anvil and stirrup." This usually occurs as individuals age and may have a familial predilection. Hearing aids may improve hearing in both otosclerosis and NIHL.
Hearing Aids in Pilots and Controllers
Note that a pilot/controller may take an FAA PE while using a hearing aid. If they take a hearing test with a hearing aid in place, the medical certificate usually will bear the restriction "Must use hearing amplification." This means the pilot/controller has the option of using a hearing aid while flying or controlling, using a headset, using an earpiece or an overhead speaker system.
However, there are differences between airmen and controller standards. The concern for controllers is that an ear piece is in one ear and the other ear is used for communications within the tower cab. For this reason, the FAA will not allow unilateral deafness in controllers. There are some regional variations in this policy. If a controller doesn't meet audiogram standards, then they are required to pass with 70% for speech discrimination. They also require supervisory statements and then can be given Special Consideration for controlling.
Colds, Ear Blocks and Hearing
Colds and ear blocks decrease the ability of the ear drum to move fully with sound pressure waves. This temporarily reduces hearing. Hearing should return to normal when the condition is improved. Decongestants will also improve the hearing. Be cautious of trying to fly with decongestants to "clear the ears." Although this practice may allow a pilot to take off safely, problems are frequently encountered as ambient pressure rises on descent. The risk is an ear block, with possible vertigo or a ruptured ear drum. Both are very unpleasant and potentially compromise flight safety. A pilot may consider having a bottle of Afrin or neosynephrine nasal spray as an emergency "get me down" treatment but should never fly if this medication is required to clear ears prior to flight.
Other Causes of Hearing Loss
Less common causes of hearing loss may be more profound in one ear and may indicate the need for thorough medical evaluation. Two of these conditions have serious implications for a controller or pilot?s medical certificate, but evaluation should not be delayed for fear of "having the medical ticket pulled."
The first condition is an acoustic neuroma. This is a tumor of the eighth cranial nerve that provides hearing and balance inputs to the brain from each ear. This type of tumor is usually slow growing but must be removed. It is detected by a CT or MRI scan, although sometimes may be seen by looking directly in the ear. Surgery is usually curative although hearing may be permanently affected and balance temporarily affected depending on the amount of nerve preserved at surgery. Again, FAA hearing standards allow the use of BOTH ears to pass, not just EACH ear. A pilot/controller could be completely deaf in one ear and still meet FAA standards. This may present problems in the cockpit using an earpiece in one ear for radio communications and spoken voice for crew cockpit communications.
The other serious cause of hearing loss for aviators is Meniere?s syndrome, sometimes known as endolymphatic hydrops. Classically this usually presents as a triad of sudden unilateral hearing loss, roaring tinnitus and episodic vertigo. Not all three components are required for this diagnosis. Obviously, the sudden, unpredictable vertigo associated with this syndrome presents a safety risk to a pilot/controller. The condition is disqualifying for all classes of certification.
Some treatments may allow recertification after the condition is resolved. One treatment involves the use of salt restriction and diuretics (fluid pills) since one theory about the cause involves excess fluid in the components of the inner ear. Another treatment is the surgical construction of a shunt to remove fluid from the inner ear. Surgery should be done at an medical center experienced in this condition. Both treatments have variable results. For favorable review of a medical application in a pilot/controller with a history of this condition, they must be free of vertigo for an extended observation period. Provocative testing of balance (posturography) and vertigo using an ENG (electronystygmogram) may be required. The FAA will require periodic reports from the monitoring physician of an individual with a history of Meniere?s syndrome.
FAA Hearing Standards
The current FAA hearing standards for all classes of certificate (FAR 67.105, .205, .305) require an airman to hear the SPOKEN voice at six feet using BOTH ears with the pilot's back turned to the examiner. Previously the standard was the WHISPERED voice using EACH ear at 20 feet, six feet and three feet for First, Second and Third Class certification, respectively. For those airman who can not pass this test, two other tests are authorized. One is a speech discrimination score of 70%. The other is audiometry (hearing using pure tones in a headset) as below:
The best solution to preserving hearing is to protect yourself from hazardous noise. If you do experience a hearing loss, get it evaluated by experts. Rest assured that the FAA will generally certify or waive most pilots/controllers with significant degrees of hearing loss, assuming the condition is stable and not associated with ongoing vertigo.
An excellent, concise article on this subject was published in the Federal Air Surgeon's Medical Bulletin titled Hearing and Noise in Aviation by Dr. Melchor Antuņano and James Spanyers.
VFS Aeromedical Assistance
For a more specific personal explanation to your questions or those concerning aeromedical certification, contact VFS for a private consultation. For help in reporting treatment for and obtaining clearance from the FAA to fly and control with these conditions, refer to the VFS Confidential Questionnaire. If you are a VFS Corporate Member, these services are FREE to you.