Airliner toilets can be scary things. When they flush, they sound like they'd like to suck you in along with everything else. Frequent fliers can take heart, however, as scientists have created a commode system that is claimed to reduce flush noise by almost 50 percent.

In order to use as little water as possible, airplane toilets utilize a vacuum to help pull air and liquid down at nearly half the speed of sound – reportedly over 300 mph (483 km/h). It only follows, therefore, that any obstructions to that flow will result in significant noise.

Led by Prof. Kent Gee, physicists at Utah's Brigham Young University set out to design a retrofit system that minimizes those obstructions. This involved adding piping that increases the distance between the toilet bowl and the flush valve, and replacing the sharply-angled pipe attachment at the bowl with one that's more gradually bent.

When installed in an existing airplane toilet, the system is said to have reduced aeroacoustically-generated noise by up to 16 decibels when the flush valve started opening, and by five to 10 decibels once it was fully open. Installation is claimed to be fairly simple, as only the elbow pipe needs to be taken out, with the bowl and valve staying put.

The technology – which is now being commercialized with help from an industry partner – could also find use in cruise ships, trains, or even eco-friendly buildings in which water use is being minimized.

"Airline companies have always had standards for the toilet noise, but they've never met those and there has never been much pressure to do so," says research partner, Prof. Scott Sommerfeldt. "Now with the reduced cabin sound levels, the sound of the toilet flushing is more noticeable and customers are pushing back."

A paper on the study was recently published in the journal Proceedings of Meetings on Acoustics.