Oi! You! Listen Up! – 30% of Pilots have Hearing Loss
Every morning, afternoon and evening, I shout at John. I yell at him 7 days a week. I repeat myself over and over again when we are somewhere where we have to be quiet. Some would call it nagging, some would think I am being hostile to John, disrespecting him. Instead, I shout at him because I care for him. Sometimes, I just feel like a fog horn.
The truth is, John has severe hearing loss having been a pilot for nearly 50 years and from working in a noisy carpet making factory when he was a teenager as he raised funds for his flight lessons.
Despite wearing state of the art hearing aids, he can’t hear his grandkids talking to him, he can’t understand what strangers say to him and he can’t participate very well in social occasions. Going to plays, the theatre and movies (something that John loves) has become purgatory. Loud environments, like cafes and restauraunts ruin his social life. When we are out on our bikes, I ride behind John as he can’t hear the rush of potentially oncoming death – I call out that there is traffic approaching so he can be ready for it.
Nothing can be done for him.
But what about for you?
Essential Disclaimer: I am not an audiologist, however, I have been a researcher for decades. All data in the below article is drawn from scientific papers which will be referenced at the end of the article.
Eh?
NOISE 101
Noise is measured in units of sound pressure called decibels (dB). Frequency (Hz – the ‘pitch’ of the sound – e.g. a high pitched squeak or a low pitched boom), intensity (volume), duration (how long) and type of noise (constant or impulse like) have different impacts on the ear.
Frequency is the physical property of the sound wave. Humans can hear sounds between 20 and 20,000 Hz.
Intensity can vary between a whisper of wind to the ear destroying sound of a rocket taking off.
Duration is how long the ears are exposed to the noise.
Type of noise can be an unexpected loud sound such as a balloon bursting or background white noise.
HOW THE EAR WORKS
John Hopkins Medicine – a respected institution based in America, educating doctors, has an excellent description of how the ear works.
The Outer Ear
The auricle (pinna) is the visible portion of the outer ear. It collects sound waves and channels them into the ear canal (external auditory meatus), where the sound is amplified.
The sound waves then travel toward a flexible, oval membrane at the end of the ear canal called the eardrum, or tympanic membrane. Sound waves cause the eardrum to vibrate.
The Middle Ear
The vibrations from the eardrum set the ossicles into motion. The ossicles are actually tiny bones — the smallest in the human body. The three bones are named after their shapes: the malleus (hammer), incus (anvil) and stapes (stirrup). The ossicles further amplify the sound.
The tiny stapes bone attaches to the oval window that connects the middle ear to the inner ear. The Eustachian tube, which opens into the middle ear, is responsible for equalizing the pressure between the air outside the ear and that within the middle ear.
The Inner Ear
The sound waves enter the inner ear and then into the cochlea, a snail-shaped organ. The cochlea is filled with a fluid that moves in response to the vibrations from the oval window. As the fluid moves, 25,000 nerve endings are set into motion. These nerve endings transform the vibrations into electrical impulses that then travel along the eighth cranial nerve (auditory nerve) to the brain.
The brain then interprets these signals, and this is how we hear.
To understand the nerve endings in the cochlea, think of them as stalks of corn growing in the field and the fluid that moves over them as the wind that blows across the corn. If the wind is strong the corn begins to move vigorously and if a hurricane comes through the stalks are flattened down to the ground and can no longer move. It is the same with the nerve endings in the cochlea. Once they have been ‘pushed over’ by loud noise, they can no longer operate. The more often loud noise is sending strong vibrations across the cochlea, the more nerve endings stop working. The more nerve endings out of action, the less you hear.
Do you hear what I’m saying?
Sound meters were developed in 1960 and at that point noise sources began to be identified as to which were comfortable, uncomfortable and which were dangerous to the ears.
Quiet human breathing - 10dB - Each 3dB increase, hereafter, is a doubling in the level of noise.
Normal conversation - 60dB
Shouting directly into the ear - 110dB
Listening to music on headphones loudly - 112dB
Rock Concerts and Jet Engines idling on the ramp - 120 dB
Jet taking off – 150dB
Rocket taking off – 189dB
(Data provided by International Noise Awareness Day)
WHAT SOUND LEVELS ARE SAFE?
The National Institute for Occupational Safety and Health (NIOSH) in the States has recommended that all worker exposures to noise should be controlled below a level equivalent to 85 dBA for eight hours to minimize occupational Noise Induced Hearing Loss (NIHL). Every 3dB increase above 85dB is only safe for half the time (eg, 88dB is only safe for 4 hours, 91dB is only safe for 2 hours).
Here in New Zealand, Worksafe agrees with this and goes further by adding that they predict that 95% of people working in this environment for 40 or more years will suffer hearing loss. (Approved Code of Practice for the Management of Noise in the Workplace 2002).
Now, 40 years sounds like a long time, especially when you are young. But if you start learning to fly at 16, or even 25, and intend on being an airline pilot, you will be exposed to noise exceeding safe limits for more than 40 years, especially if you take into account the current retirement age is 65 years.
WHAT SOUND LEVELS ARE FOUND ON COMMERCIAL AIRCRAFT?
Here is where things get tricky. The study of airline pilot hearing loss is minimal with only about a dozen out there. But the studies are damning. FAA and other aviation bodies, as well as airlines, will say that the ambient dB inside an airliner is between 74dB and 80dB. The more modern the aircraft, the less noise (in theory). However, the airlines questioned for the study admitted these were on ground measurements. A little disingenuous considering when pilots are working on board, the aircraft is most often NOT on the ground. Moreover, window seats were found to be 4dB louder than other seats. Now consider the fact that the tech crew sit with windows surrounding them in a 180 degree arc. The noise of airflow across the fuselage is adding to the noise at these locations.
HOWEVER, according to a paper published in the British Medical Journal in 2017, a large German airline actually used readings taken AT the pilot’s ear (as in, inside the headset) and found that the levels there were between 84 and 90dB. At 88dB, this level is only safe for a maximum of four hours. These levels under the headset are up to 11dB higher than the ambient cockpit noise which airlines and manufacturers quote. The reason for the increase in dB between the ambient and headset intensity is that ATC comms need to be heard clearly above the ambient noise of the flightdeck.
The closest comparison I could find for a typical 14 hour longhaul flight from New Zealand to the North American Continent were the recordings taken in a B747 cockpit over 19 hours on a return duty – 9.5 hours flight time per flight. Using these figures and extrapolating out the figures for the 14 hour flight (28 hours return duty), the pilots are exposed to ambient flight deck noise of 80dB for the 14 hour flights and, in addition, ATC transmissions in the headset of 88dB averaging about a third of the flight time (so, about 4.5 hours). This shows that on most flights across the Pacific, pilots are being exposed to noise levels that are unsafe and are damaging their hearing on each duty. Remember that only 8 hours is the guideline for duration of exposure up to 85dB, and 4 hours for 88dB.
The left ear, you say?
Now here’s a twist. Pilots will most likely have a disparity in their hearing loss. Left ear as opposed to right ear. Brazilian, Turkish and German studies have shown that when it comes to Noise Induced Hearing Loss (NIHL), airline pilots have a unique hearing loss profile not experienced by those in ground based industries.
The studies showed that the worst hearing loss is more often in the left ear, for pilots. The damage becomes apparent above 5000 flight hours and/or more than 10 years on flight service. If you fit either of these statistics, it’s time to get your hearing tested.
Discussion around the left ear bias is interesting. Seat positions by flight deck windows are considered, especially for Captains who are generally older. Human physiology may count some way towards this (think about one hand being more proficient than the other – being ‘righthanded’) but significant consideration is given to headset positioning choice.
More than half of pilots use both ears for radio comms, a third use the right ear only. These pilots are First Officers and therefore are most often under the age of 40 where hearing loss is not yet obvious. 10% prefer to use the left ear and these pilots were all captains, the vast majority of them over 40 years old,
The choice to use only a single ear for comms is so the pilot can communicate more easily with the other pilot.
Both or single?
Then we get into a vicious cycle of headset induced hearing loss. As flight times increase, flight hours accrue and length of airline service increases, hearing loss also increases. But it’s a silent saboteur. Permanent hearing loss first occurs in sound frequencies in the vicinity of 4,000 Hz which is outside the conversational range (500 – 3,000 Hz) so affected people are not aware their hearing is damaged until others tell them, or they have a gradual realisation that others can hear better than themselves. By then, it’s too late.
As tech crew start to lose their hearing, they turn up the volume in their headset to hear better. This simply pushes more noise further into the ear, flattening more nerve endings in the process, making the pilot even more deaf and they turn up the volume in the headset….
IS PILOT HEARING PROTECTED BY LEGISLATION?
Unfortunately, that is a big fat ‘NO!’ In 2013, the FAA policy statement required that airlines must protect the hearing of cabin crew but specifically not pilots. Individual pilot hearing integrity has been sacrificed on the alter of public safety.
Sorry Pilots - we ain’t going to protect your hearing
Here in New Zealand, the Key Government in 2015 signed over responsibility for air crew health and safety to CAA, thus removing any regulation for in-flight workplace injury from Worksafe’s jurisdiction. I took a look at the CAA legislation around Health and Safety of aircrew. The document is heavy on safety requirements but is deafeningly silent on aircrew health – such as hearing. I would love to be proven wrong.
AND WHAT ABOUT ACC COVER?
The Tui ad comes to mind – Yeah Right! Or more colloquially – Yeah, Nah!
Ostensibly, workplace NIHL is covered but anecdotally (with our own experience and the stories of many pilots of John’s era), ACC will decline cover.
Long story short, we fought ACC as far as a ‘third party’ dispute hearing (funded by ACC so not quite as independent as you’d hope). They gave us the option to proceed to the District Court but gave us a deadline which the only aviation audiologist in NZ could not meet.
Yeah, Nah…
To keep emotion out of it, I will simply advise that we provided all studies and papers we could find on pilot hearing loss and the environment they work in. No study found that pilots are not in danger of hearing loss. The only argument between the studies was in how much danger for hearing loss?
However, ACC will not accept evidence provided by non-qualified people – even if they are only bringing scientific evidence to the table for ACC experts to read. We felt this was deeply unfair as we found the ACC’s audiologists are not experts in aviation medicine and appear to have zero understanding of the flight deck environment. They did not read the scientific papers or studies that we provided to help them increase their understanding. They only made decisions based on their own knowledge of ground based industries.
ACC’s main expert went so far as to say that John had only a limited history of working in a noisy environment. John worked as an airline pilot for nearly 40 years. He also said that John suffered from accelerated presbycusis rather than NIHL.
The cause of accelerated presbycusis is chronic exposure to loud noises. The cause of NIHL is…. Wait for it… Chronic exposure to loud noises. NIHL is covered by ACC (in theory) but not accelerated presbycusis. Do you see the difference? No, nor do we.
Check out the theories of Occams Razor and the Dunning Krugar Effect to see how unbelievable their actions were and how the idea of ‘Good Faith’ was ignored.
And the basis for no cover? Cover was declined because John’s hearing loss was worse in his left ear which was incompatible with the ‘experts’ understanding of Occupational NIHL (the understanding being that both ears are exposed to the same levels of noise in a workplace environment). This decision was made after we provided the evidence of why a pilot’s left ear is more likely to have worse hearing loss.
ACCs experts also argued that occupation NIHL is caused early in a career – unlike the studies for airline pilots that have found NIHL increases with increase in flight hours. These studies have shown that NIHL starts after about 5000 hours and gets progressively worse. John had more than 25,000 hours by the time he retired.
Shhhh!
WHAT CAN YOU DO TO PROTECT YOUR HEARING?
If you are a young person hoping to be an airline pilot, take care of your hearing now. Reduce the volume in your ear phones when gaming or listening to music. Wear ear plugs to shows and concerts. And if your flight school doesn’t provide noise cancelling headsets, invest in a pair for yourself. Keep the volume of the your TV down.
If you are already flying commercially, make sure the headsets provided are noise cancelling. Take care of your ears when not flying – wear ear plugs to noisy environments and when completing noisy work at home – lawnmowers, chainsaws etc. make sure to wear the headset over both ears when on the flight deck.
Ask your union what they are doing to protect your hearing in the workplace?
Get a hearing test annually for your own peace of mind and work with the test results – are you willing to give up flying if your hearing is showing an intolerable level of decline
Don’t end up like John,
REFERENCES
Noise Levels and Communications on the Flight Decks of Civil Aircraft (PDF) chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://generic.wordpress.soton.ac.uk/isvr-new/wp-content/uploads/sites/422/2022/07/Inter96air.pdf
FAA Hearing and Noise in Aviation (PDF) chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.faa.gov/pilots/safety/pilotsafetybrochures/media/hearing.pdf
Audiometric Profile of Civilian Pilots According to Noise Exposure https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4211569/
Evaluation of Hearing Loss in Pilots https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5782980/
Noise Exposure and Auditory Thresholds of German airline pilots: a cross-sectional study https://bmjopen.bmj.com/content/7/5/e012913
Recent Advances in the Study of Age-Related Hearing Loss https://karger.com/ger/article/58/6/490/149044/Recent-Advances-in-the-Study-of-Age-Related
