Airplane bathrooms are uncomfortable—they’re cramped, they stink, and the flush is so jolting it feels like you might get sucked out.
But the shrieking airplane toilet might be a relic of the past. Researchers at Brigham Young University have invented the quietest toilet ever, according to a new paper published in the Proceedings of Meetings on Acoustics.
Scott Sommerfeldt, a physics professor at Brigham Young, said that the idea grew from a comment by a major manufacturer of aircraft toilets who noted his child was terrified of the whooshing sound. Adults aren’t exactly big fans either.
“It’s startling and irritating, like you might get sucked down the toilet,” Sommerfeldt told The Daily Beast. “There’s been an increased emphasis and push to get toilets down to quieter noise levels so they’re not as annoying for passengers.”
Two years later, Somerfeldt and his team have registered three patents for a toilet powered by a vacuum that’s about 50 percent quieter than a standard airplane toilet.
The journey to a more hushed flush wasn’t easy. The airplane toilet as we know it is 25 years old and represents the unique aerodynamics of processing human waste in mid-air. Airplane toilets can’t use much water and require a vacuum to help suck out waste.
Somerfeldt said the sucking action contributes to the noise; at 38,000 feet, the vacuum has to pull waste at about half the speed of sound, around 300 miles per hour.
There was another problem: Airplane toilets have a sharp bend in their piping, making an already loud process even louder.
Adding pipe between the bowl and the flushing valve cut the noise by 16 decibels. Another way to muffle the flush was to slope the pipes more to eliminate the sharp bend, saving another 5 to 10 decibels.
“With those things together, we can bring noise down to ambient noise—basically the same as the airplane itself,” Somerfeldt said.
What makes the toilet even more attractive is that it can be retrofit into existing airplane toilets by swapping the old elbow pipe for the new one. “It takes us 10 minutes to do,” Somerfeldt said, adding that an expert plumber could make the switch in even less time. “And if it [the valve] needs cleaning or gets clogged, it’s easy to just snap it.”
A quieter toilet has applications beyond planes: think trains, buses, and even cruise ships.
They might also find a place in green homes. “It’s a smaller market right now, but it’s got potential,” Somerfeldt said.
Somerfeldt said the lower-volume lavatories need approval by Federal Aviation Administration. Once that happens, assuming airlines buy in, passengers could be flushing with abandon within a year.