"People have told us they don't want their kids to be scared to use the bathroom on a flight," lead researcher Kent Gee recently told Eureka Alert. "So, we've used good physics to solve the problem."
Airplane toilets are extremely loud when flushed as they rely on lots of suction to transfer waste but very little water into a holding tank. The powerful force of suction can very briefly move water at speeds of over 300 miles per hour. Any disturbance in the flow — including a bend in the pipe — increases the dreaded brutal bellow.
In a paper titled "Noise Reduction of a Vacuum-Assisted Toilet," published in December 2018, researchers reduced the flushing scream by simply increasing the distance between the flush valve and the toilet bowl by means of an extra piece of pipe. In addition, the toilet testers — for science! — found that reducing the sharp angles of the plumbing that connects the toilet to the aircraft's holding tank also lowers the spectacular sonic attack.
"Three stages of noise can be correlated with three flush valve conditions during the flush cycle: an initial noise level peak associated with the flush valve opening, an intermediate noise level plateau associated with the valve being fully opened, and a final noise level peak associated with the flush valve closing," the paper's abstract carefully explained.
"It was hypothesized that increasing the distance between the flush valve and the bowl and increasing the bend radius of the attachment at the bowl exit reduces overall noise levels. These modifications resulted in a 13 to 16 decibels reduction in the noise radiated from the bowl during the valve opening and closing in addition to a five to 10 decibels reduction in the noise radiated from the bowl during the open valve condition," the paper adds.
The new science of quiet will be welcomed by almost everybody, although those patiently waiting in the aisle of a plane for their turn to pee will now have to listen more closely for that joyful noise indicating that their painful wait is soon to be over.