Hearing loss caused by noise is a huge problem for all pilots and flight instructors, especially those who fly small aircraft. Think about it: Day after day, flight after flight, pilots are subjected to a constant din from the engines, exhaust, propeller, fuselage and other areas. And unlike other noisy professions, pilots are generally subjected to the same noise frequency and intensity for extended periods of time. Here are some important things to know about noise fatigue, and how you can help prevent long-term hearing loss.
While noise fatigue is a health issue for all pilots, small aircraft, especially turboprop planes, are generally noisier and less insulated than large commercial jet aircraft. Even if you fly a larger aircraft with a quieter interior, you are probably exposed to ambient noise from the tarmac or in the cockpit with the cabin door open. Most noise inside and around the aircraft are from four main areas:
- Noise from the exhaust stacks (especially short stacks) usually located directly beneath the cabin, and the subsequent airflow pushing up against the bottom of the fuselage
- The propeller and airflow off the propeller against the windshield
- Airflow through vents, leaks around doors and turbulence throughout the fuselage
- Engine noise, especially the vibration of air-cooled engines
Average Everyday Decibel Levels
The decibel (dB) is the unit used to measure sound intensity. To give you an idea of the average decibel level of some everyday sounds, consider the following:
- A whisper – 30 dB
- A quiet room – 40 dB
- Normal conversation – 60 dB
- Busy traffic – 70 dB
- Gas lawn mower – 106 dB
- Jackhammer – 130 dB
- Jet engine – 140 dB
Keep in mind that permanent hearing damage can occur from sounds louder than 85 dB, physical pain occurs at around 125 dB, and an eardrum may burst at 140 dB. The Occupational Safety and Health Organization (OSHA) states that the maximum level of "safe" exposure to loud sounds is 90 dB for up to eight hours, or 100 dB for up to two hours. OSHA requires that workers exposed to noise levels higher than 85 dB must use hearing protection equipment.
Study on Aircraft Noise Levels
In 2010, an Occupational Health & Safety study entitled, "Interior Sound Levels in General Aviation Aircraft" sought to determine if prolonged exposure to interior aircraft noise is a health hazard for pilots.
For the study, sound samples were taken in a Cessna 172 and a Piper PA-44 Seminole – two planes with different airframes. While the planes were in flight, two sound-level meters took readings from within an occupant's headset, as well ambient noise from the cabin, to get an idea of true noise levels without any hearing protection.
To simulate a "worst flying day scenario," the researchers tested for eight-hour exposure, and created an eight-hour time weighted average from the sound sample readings. The time-weighted average for all of the aircraft cabin measurements came in at 86.26 dBA. The study's data reinforced that pilots are indeed exposed to sound levels higher than OSHA standards. The study also determined that the use of a headset is adequate hearing protection for a projected eight-hour period. Read the full study . To get an idea of the decibel level inside your aircraft, buy a decibel meter at an electronics store and (safely) take readings during the climb, cruise and descent. Keep in mind the dB level inside your headphones should be lower than the ambient, unprotected noise level in the cockpit and cabin.
Tips for Protecting Your Ears
If the ambient noise level inside your cockpit reaches 90 dBA, you should be using hearing protection equipment. A good set of headsets are essential, especially if in-cockpit noise levels exceed OSHA exposure limits. Active noise reduction headsets are recommended because they improve signal-to-noise ratios and enhance sound quality. Another benefit of a quality headset is that they reduce high-frequency background noise, making speech signals clearer and easier to understand. For maximum protection, combine a good set of active noise reduction headsets with earplugs. Another good tip is to limit your exposure to loud activities before flying, such as mowing the lawn or listening to loud music.
If You Have Symptoms of Hearing Loss …
Some symptoms of hearing loss include difficulty understanding what people are saying, listening to TV and music at loud levels and avoiding social interactions because hearing is frustrating. Prolonged exposure to loud noises and unchecked hearing damage can also cause irritability, lack of focus, high blood pressure, increased stress levels, insomnia and high or abnormal heart rate.
If you suspect you are suffering from hearing loss and its side effects, see your doctor and / or get checked by a qualified otolaryngologist or audiologist to find out the extent of the hearing damage, if any, and what you can do to treat it.