I have been completely deaf in my left ear since being hit by a car when I was two years old. Since I’m operating with no backup, I do basic things to protect my one good ear like carrying ear plugs to concerts and plugging my ear when a fire engine drives by.

Flying is always a loud experience, of course, so I travel with high quality earplugs and over the ear noise-canceling headphones that, combined, can reduce the ambient roar of an aircraft cabin to a comfortable hum.

Of late, I’ve been on flights where the sound of the flight attendants over the PA system was loud enough to sound like the attendant was shouting directly into my ear despite having two layers of sound protection. So, I decided to gather some data on my next flight.

On Sunday, I boarded UA697 from LAS to SFO and opened the decibel meter on my iPhone. Before we get to the results, however, I’ll quickly recap how sound volume is measured.

Decibel scale

The decibel (dB) is a base 10 logarithmic scale. That means if I want to increase the volume of a set of speakers from 70 decibels to 80 decibels, I must provide 10 times as much power. To increase from 70 to 90 decibels requires 100 times the power. The point is: a 10dB volume increase is a big jump, indeed.

Here are some interesting benchmarks to calibrate with:

47dB: My office at 42Floors (after everyone has gone home)

65dB: Conversation in office

73dB: Inside my Jeep at 65mph

88dB: Food blender

90dB: OSHA monitoring requirements

96dB: Lawn mower

110dB: Car horn at 1 meter (physical pain threshold)

150dB: Jet take-off at 25 meters (eardrum rupture)

United flight 697

So how loud was my flight? The background noise was a typical 84dB in flight: newer planes like the Boeing 787 are quieter; turboprop planes are louder.

What shocked me was the volume of the PA system. Each time the flight attendant made an announcement, I whipped out my phone and sampled the volume level: peaks of 96dB.

During the obligatory “Please remain seated until the aircraft comes to a complete stop,” announcement while taxiing (engines powered down) the volume reached 99dB.

That’s louder than driving a power lawn mower down the middle of the aisle.

Having no retroactive measurements, I can’t prove it, but I have a hypothesis: aircraft PA systems have been turned up higher and higher in lockstep with the proliferation of iPhones and iPads on flights.

What’s to be done?

First, you could fly a different airline. I’ve noticed Virgin America flights are quieter and I’ll be gathering measurements on future flights to test that observation.

Second, if you’re in the airline industry, you can measure the volume yourself on your next flight and point it out to your OSHA representative. If enough people do that, we’d likely see the airlines self-administer a reasonable volume maximum around 90dB.

Given that background jet engine noise and human speech frequency ranges do not overlap, the PA system does not need to be louder than the engine to be heard clearly.

Protect your stereocilia, people! Stem cell research might not be able grow you new ones in time.