Air pressure and the human ear

By Frederic Friedel

Some years ago I was in California, and our friend Ken Thompson, who owns a small Cessna, offered to fly us over the Sierra mountains, the canyons and the lakes. It was an offer we could not refuse — especially since my wife is a geologist and deeply interested in the Western geographical formations.

There were some problems with the trip. Ken has heart problems, so I insisted he teach me (1) how to operate the radio to make emergency calls; (2) how to basically land a plane; and (3) how to open the door and push out a dead pilot. He showed me the first two but said it was impossible to open the door during flight. We would have to simply leave him slumped in his seat.

When flying over the rugged Sierras I asked him what would happen if the engine of the plane failed. “They don’t fail,” he replied. “But it’s just a souped-up car engine,” I insisted, “and they do fail.” “Well, if it fails you glide for as long as you can, and look for the best place to — crash.” Ken is not a reassuring person.

Everything went well and Ingrid got a thousand aerial pictures of the mountains, Las Vegas, Grand Canyon, Monument Valley, Death Valley, Brice, Sion, the lakes. It was truly amazing, and I will describe it in a later article. Unfortunately there was a problem with my ears.

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The human ear is a badly engineered organ: it is hideously complex, with sound causing a membrane, the eardrum, to vibrate, and the motion conveyed through three tiny bones called the hammer, anvil and stirrup (malleus, incus and stapes), to the cochlea, a snail-shaped organ that registers the movement of the stirrup with the help of hairs in its liquid content. Just for fun the cochlea moonlights as a balance organ: it has three semi-circular canals called the vestibular system, oriented in three dimensions of space. They are filled with liquid and the organ monitors the movement of the liquid due to inertia when the head or body is moved. I kid you not.

Now comes the construction error: the eardrum is a tight seal to the space behind it, so that any increase or decrease in air pressure will cause it to move inward or outward, and actually burst, if the pressure difference is too high. In order to avoid this, evolution installed the Eustachian tubes which allow air from the throat to balance the pressure coming from outside the eardrum. Nice, except that the Eustachian tubes are often blocked, preventing a free flow of air. Which is exactly what happened to me, flying over the Sierra, well over 12,000 feet, with a heavy cold closing my tubes. It was quite painful, and I was basically deaf on one side when we landed in Colorado.

After that, on subsequent flights over the canyons, the ear felt okay when we were high up in the air, but became painful when we landed. Clearly the pressure behind the eardrum was lower than the outside pressure at sea level, which caused considerable discomfort. I asked Ken if we could stay aloft for a few days, but that was apparently impossible. So I continued to have trouble until we got back to our base in San José. Immediately after returning I was on a flight back to Germany. Once again I was okay at cruising levels, but landing caused pain and deafness.

I went to the ear specialist as soon as I arrived. He found that there was possibly infected liquid behind the eardrum, and recommended immediate tympanostomy — the insertion of a small tube into the eardrum in order to drain the middle ear and keep it aerated, and to prevent further accumulation of fluid there. The tube they used on me was made of gold, and it was scheduled to fall out in a couple of months. I carefully checked my pillow every morning, but I never found it. Big disappointment.

The treatment worked fine — instant relief, only a slight degradation of hearing with the tube in place. And no problems since. But I realized that the whole hearing system is simply too volatile: the pressure release through the Eustachian tubes is not reliable, which is why so many children have to undergo tympanostomy to relieve blocked tubes. Researching the subject I also discovered that German pilots during the war intentionally ruptured their eardrums (with nails) to prevent problems during their extreme flights; and that the Bajau people of the Pacific do the same, at an early age, to facilitate diving and hunting at sea. Shiver, shiver.

While we are still feeling queasy, here’s something I have witnessed in India: on the streets there you often see people having their ears cleaned, by professionals whose tools are a sharp steel needle, a wad of cotton and a pair of pincers to remove any loose wax. Below are some images — a full description is available on this Mail Online page.

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Watching scenes like this in towns and villages I was myself tempted to give it a go — but lacked the nerves to do so. Uwe, a fellow tourist, also German, was braver and had his ears cleaned by a roadside ear doctor — and lived to tell the tale. I have a picture somewhere of the procedure which I will add to this report if I ever find it.

I want to end on a positive note: not too long ago I was shopping in a Spanish supermarket and noticed that the owner, who was explaining products to me, had a sort of button attached to his scalp. I can never resist, and so I asked him what that was about. “It’s a cochlea implant,” he said.

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A cochlea implant that restores or makes hearing possible in the deaf (see UNC report)

Apparently this man had lost his hearing in an “antibiotic accident” and had received an electronic implant that sent sound signals to his cochlea, stimulating the auditory nerve hairs directly, within the organ. He spoke normally, which was an indication that he had not been deaf since childhood. I held my hand in front of my mouth and said: “Can you now hear everything I say?” Yes, sure, he answered. So he was not lip-reading. “Were you totally deaf?” I wanted to know. “Oh yes, and I still am,” he said, detaching the button from his head (where it was magnetically held). “Now I can hear absolutely nothing, not a sound.” Again I held my hand in front of my mouth and spoke loudly. This time there was no reaction.

This is a truly marvellous development, and if you want to finish this read on a really high note you should go watch some videos of cochlea implant patients, especially children, hearing for the first time. Here’s one for starter — try holding back your tears while you watch it:

Written by

Frederic Alois Friedel, born in 1945, science journalist, co-founder of ChessBase, studied Philosophy and Linguistics at the University of Hamburg and Oxford.

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