There are things from our collective past that leave me gobsmacked. Homes were tinted (and tainted) with lead paint. Cigarettes were promoted for their health benefits. Baby cribs had widely spaced bars and plastic-covered mattresses poised to suffocate our curious, but weak, offspring. Kids who survived their cribs grew up to throw finned metal spikes into the air for sport. And we flew without hearing protection, which strikes me as shortsighted. Here are the advances I’ve seen in cockpit noise reduction over my 40-year flying career.
Arthritic Finger Communication System
When I recall my flying lessons from 1980, I recall fumbling for a Cessna’s mic while distorting my face to decipher the distorted sounds emitting from the overhead speaker. My 16-year-old ears struggled to hear the tower correctly. Or at all. More than once I defaulted to my instructor’s well-developed interpretations of the speaker’s eruptions. Although he lost most of his hearing navigating B-17s between England and Europe, he was proficient at deciphering the garbled messages or, more likely, he knew what the controller was saying without having to hear her. I’m not sure he was aware he was guiding me into and out of controlled airspace with small gestures from an arthritic finger: Continue, turn left, turn right, climb, descend.
On my solo flight the speaker emitted a lengthy directive as I ascended from my second touch and go. The word count exceeded “Seven, zero, four, November, papa, clear touch and go runway niner.” Without an arthritic finger to guide me, I flew left traffic rather than right traffic on that pattern. The speaker remained silent. My interpretation skills were improving. However, I left the microphone, tethered to the panel by a coiled cable, exploring the floor like a dog on a leash. With my hands full trying to stay alive, I gave up getting the microphone back in its holder. So many unnecessary distractions to the task of learning to fly.
Passive Noise Reduction
By the mid-1990s, general aviation had largely moved beyond hand gesture communication and squinting to hear critical commands issued through a transistor radio speaker. The Cessna I rented was equipped with headsets that placed a speaker by each ear and blocked some of the ambient noise with semi-padded ear cups. An integrated microphone was a bonus; it remained poised by my lips rather than roaming the cockpit floor, and a single finger could activate a transmission—a task that once required a whole hand. The headset aided communication but was so uncomfortable that within 30 minutes of taking flight it felt like I had awoken with my head stuck between the bars of a crib. I suppose that kept the headsets from walking away from the airplane and guaranteed the airplane would be back on the ground on time for the next hourly renter.
What Is Noise?
The noise in a cockpit is generated mostly by the propeller thrashing the air and the airflow interacting with every rivet, bolt head, airframe intersection, the gaps in the cowling and canopy, the flying wires and antenna. In short, noise is turbulence and it is generated by every surface imperfection on the airframe as the propeller wraps its sonic signature around the entire airframe.
In my career in the kit plane industry, I saw many homebuilders try to attenuate cockpit noise by adding sound-deadening insulation to the opaque surfaces of the fuselage’s interior. I’d compare that to insulating the walls of a home that has only screen doors and windows. The hurricane-force wind is also playing against the 1/8” thick windshield, plexiglass windows, or canopy. What the insulation is doing, I’d argue, is adding weight to the airframe, increasing building time and cost, covering items that may need future access, promoting corrosion, and providing nesting material for critters. Rather than insulate the walls of a home that has bad doors and windows, you’d be further ahead giving everyone a blanket. Rather than soundproofing the floor and walls of the cockpit, you’d be better off with good headsets.
Active Noise (and Weight) Reduction
When I began flying my Sonex, Metal Illness, I equipped myself with an expensive pair of passive noise reduction headsets. They were comfortable and performed well, but I replaced them the moment I experienced active noise reduction (ANR) headsets. ANR headsets make the cockpit a far more pleasant place to be, dropping the cockpit sound level below what I experience in the cabin of a commercial airline. I remember the first time I removed my ANR headset in flight, to remove my hat. The explosion of noise was startling, almost frightening.
While ANR headsets block distracting and damaging noise, they can also block sounds you may want to hear. Sound is a valuable troubleshooting tool, and you should know what your airplane sounds like with the active noise canceling turned off. I had a practice of listening to my engine with the ANR off so I’d be familiar with the normal sounds. That could be useful in identifying a new sound that may indicate trouble. Here’s another tip: Carry extra batteries for your headset. While ANR headsets provide passive noise reduction, once you are accustomed to the active noise-canceling properties you won’t want to finish a flight without it, especially if you are unpracticed at distorting your face to interpret radio transmissions.
ANR headsets offer obvious advantages (clear, therefore accurate, communication as well as advanced hearing protection) and not-so-obvious advantages, like reducing pilot fatigue. They also transfer easily to any airplane and eliminate the cost, weight, and labor of attaching ineffective insulation to an airframe. Society has moved beyond lead-based paint, driving without seatbelts, and smoking for its health benefits. We should be beyond the days of flying without good hearing protection. Two things I know I will never do again: Bring lawn darts to a cookout and fly without ANR headsets.
Great article, good read. Thanks for the contributionto avbrief!
My D.C. 13.4’s give adequate sound muffling while also allowing me to hear what’s dear to my heart–the sound of a normally happy Lycoming. Too often I’ve listened to folks talking on wonderously expensive cell phones with dropouts when the technology thinks there’s a quiet moment just to lose track of the gist of the conversation. I’ll stick to my conventional headset, thank you.
Hi Tom,
To be sure, ANR headsets can’t create “silence,” like an interrupted cell phone conversation, and you’ll always hear your engine, you just hear it differently. Conventional headsets, which use only mechanical means for noise suppression, are like driving a car with the windows down. You can hear the radio, you can hear your passengers, you can hear the exhaust and the annoying rattle form somewhere in the back. ANR headsets are like driving that car with the windows up. You can hear all the same things, but better, because there is no wind or road noise. I began my flying career with D.C. 13.4s. My first taste of ANR headsets converted me to LightSpeed 3Gs, but there are plenty of ANR headsets to chose from from all the major manufacturers. I’ve heard the in-ear headsets are wonderful, too, but my ears have never been happy with any type of in-ear device.
Thanks Kerry, all good points. If I were flying a Beaver I might agree with you. Only a Cessna 185 might make me reconsider. As it is my basic Cessna allows me to hear well and communicate knowing nothing worth knowing about has been lost to my aging hearing including doors popping open and exhaust noises indicating a burnt through muffler. Easiest upgrade for me would be upgraded airbag restraints.