AircraftOwner Online

    How many experienced pilots say “I’m sorry, can you repeat that—I don’t hear very well?” Then they get the sophomoric response from the young pilots “Say what?”

    Hearing loss in pilots is almost universal and especially in pilots who learned to fly without headsets.

    When I first started instruction, the instructor had to shout over the engine noise and I still blame all my current bad habits on those miscommunications!

    Hearing loss, in the far majority of people, is due primarily to exposure to loud noise and to some extent, heredity. Loud concerts, noise from drilling, hammering, riveting, wind noises, engine noises, and supersonic prop tips all contribute to hearing loss.

    What is important for everyone to understand is that noise exposure is cumulative. So even when someone already has hearing loss, they need to be aggressive about protecting what they have left because they will continue to lose more hearing with additional exposure.

    Sound intensity is measured in decibels and the scale is logarithmic so a deference of 3 dB is approximately twice the level of sound. In additions, there is “frequency weighting” because some frequencies, particular the 2,000 to 6,000 Hertz range, cause more hearing loss than other frequencies. (For you audio techies out there, I know this is not as simple as this explanation states but this is not a treatise on sound measurements.) General conversation occurs between 500-3000 Hertz.

    To understand the decibel ratings (know as dB level), OHSA (Occupation Health & Safety Administration) standards state the 85 dB over eight hours is safe but only two hours at 91 dB. However, the EPA (Environmental Protection Agency) has identified the level of 70 dB for 24 hour exposure to protect the public from hearing loss which is significantly lower than OHSA.

    Putting this in perspective, a jet taking off has a 180 dB rating. Riveting creates a 120 db level while a car horn at about 20 feet is a 100db. Pain usually begins at about 125 dB but hearing loss can occur with as little as one minute exposure to 100 dB which is about the sound level of a cement mixer.

    It really is impossible to give a dB level of noise in an aircraft unless measured (a reasonable portable dB meter is available from Radio Shack). Piston aircraft create noise from the engine through the exhaust and vibration, propeller blades beating the air, and airflow around the fuselage. Each aircraft has so many variables with these factors that no average level really is valid but the FAA states the range is between 70 and 90 dB. (Obviously, the FAA has never measured a Stearman!) What is valid is that all most all aircraft in the piston fleet will cause hearing loss over time.

    There are no regulatory criteria for aircraft occupants in general aviation which is good by keeping government out of our lives. Unfortunately, the other side of that coin is there are neither standards nor testing for ear protection in aircraft so buyers beware.

    Everyone should wear hearing protection and the type breaks down into passive and active protection. Passive ear protection includes the classic foam plugs and standard but relatively inexpensive headsets. The foam or wax plugs work very well but must be placed in the ear properly. For the foam plugs, this means that the plug must be rolled small enough to fit into the ear so that it completely seals the canal when it expands. The molded wax or custom plastic plugs work very well and are easier to place properly albeit more expensive.

    Passive headsets do not require any fitting and my recommendation is to buy the highest dB reduction set available. It is important to buy a reputable brand since there are no government standards or testing required when bought in the civilian world.

    Active noise reduction headsets (ANR) are more problematic. Most of the audible noise in an aircraft is lower frequency which is handled very well by the electronic portion of the ANR headset. However, higher frequency, less audible noise, which causes hearing damage, is generally not reduced very well by the ANR headset’s passive attenuation. This leads to a false sense of security with ANR headsets.

    My recommendation is to use foam/wax/molded ear plugs under ANR headsets in the aircraft. This will give you the best of both worlds. When working in the hangar, use the highest passive attenuation passive ear muffs available. I recommend ear muffs in the hangar because they are easy to put on and take off which increases use even for short exposures.

            The most important point is the use of some type of ear protection anytime there is exposure to loud noise. It will help avoid those dumb jokes in the future.  < B.B.