Using Physics To Build a Quieter Airplane Toilet

Everyone uses it, so a team of researchers made the airplane bathroom much more pleasant.

airplane toilet
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Going to the bathroom is one thing that ties all of humanity together—even when we're at cruising altitude. But toilets on planes are often cramp and very loud. While space remains an everlasting issue when traveling 30,000 feet in the air, sound is something science is trying to tackle.

After two years, a team of BYU researchers have developed a a vacuum-assisted toilet approximately half as loud as the regular airplane toilet.

"People have told us they don't want their kids to be scared to use the bathroom on a flight," says lead researcher Kent Gee, BYU professor of physics, speaking in a . "So, we've used good physics to solve the problem."

Commode research has been mostly stagnant for the last quarter of a century. Longtime flyers might know of two eras—the "blue water" period, where chemical pouches known as have kept things clean, or when toilets are powered by vacuum flush technology.

One advantage of a vacuum flush toilet is that it keeps the plane slightly light. But that's come with a negative side effect of a loud noise occurring every time a person flushes. How to keep that advantage while making the airplane less intrusive? It's a challenge. The loud sound from the toilets doesn't come any machinery, but from the fact that the partial vacuum flush is operating at such high altitudes.

According to Gee and her fellow scientist Scott Sommerfeldt, an air-water mix in vacuum-assisted toilets travels at speeds faster than 300 miles per hour. Disturbing a flow at that speed generates a loud of sound. On a crowded flight, that noise can make situations less-than-ideal, and quieter cabins have only exacerbated the issue.

As with any engineering problem, the BYU team broke down the commodes into separate parts. There's the initial noise level peak, which is associated with the flush valve opening. Then the process moves on to an intermediate noise level plateau, when the valve is being fully opened. And finally, there's noise level peak which is associated with the flush valve closing.

Broken down into a process, researchers decided to add additional piping to increase the distance between the toilet bowl and the flush valve. Then, they changed the pipe attachment at the bowl towards a gradual bend, as opposed to a 90-degree angle leading to a harsh cutoff. Tests showed that the newly improved toilets dropped down to 16 decibels during the flush valve opening and in between 5 to 10 decibels with a fully open valve.

"It's a great mix between physics and engineering," says grad student Michael Rose, lead author on the team's most recent vacuum-assisted tech publication in . "The toilet is much quieter and now kids won't think they're going to get sucked out."

The team plans on sticking to toilets for now—they've already acquired three patents on the technology. But looking forward, they could see potential uses in locations as varied as cruise ships to low-income housing.

"At the end of the day, this is about using science to improve a user experience," Gee said. "It's an important part of making flights more comfortable for customers."

We could use all the help we can get.

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