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BYU physicists develop quieter airplane toilet

aircraft-airplane-flying-2105A quieter airplane toilet has been developed by a group of Brigham Young University physicists.

Conventional airplane toilets are very loud. For some passengers, the noise that airplane-toilets make when they flush can be unsettling, uncomfortable and even frightening.

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

After two years of trial and error – and three academic publications – researchers have finally invented a vacuum-assisted toilet that makes about half as much noise as a regular airplane commode.

For airplane toilets to flush with little water there needs to be a partial vacuum. At 38,000 feet, the vacuum pulls air at almost half the speed of sound. When things move at such a high speed, any disturbance at all to the flow – like the bend of a pipe – creates a lot of noise.

“Airline companies have always had standards for the toilet noise, but they have never met those and there has never been much pressure to do so,” said Scott Sommerfeldt, professor of mechanical engineering. 

“Now with the reduced cabin sound levels, the sound of the toilet flushing is more noticeable and customers are pushing back,” Sommerfeldt added.

The team added extra piping to increase the distance between the toilet bowl and the flush valve and gave the pipe attachment a more gradual bend rather than a sharp 90 degree angle. Tests of the new contraption show aeroacoustically-generated noise fell by up to 16 decibels during the flush valve opening and about 5 to 10 decibels when the valve is fully opened.

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

“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.”


Citation

  1. Michael T. Rose, Joshua F. Kilts, Kent L. Gee, Scott D. Sommerfeldt, Scott L. Thomson. Noise control of a vacuum-assisted toilet: structural vibration damping. , DOI: http://dx.doi.org/10.1121/2.0000995