Scientists have finally come up with a solution for the world's most annoying household sound
It haunts you when you're trying to eat your dinner in peace. It disturbs you when you're trying to watch TV. It even keeps you awake in the wee small hours.
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It's the insufferable, interminable drip-drip-dripping of a leaky tap. Well, scientists at the University of Cambridge have finally figured out what's causing what is almost certainly the world's most infuriating sound. Not only that, these clever clogs have also come up with a solution that could bring peace to all households.
"A lot of work has been done on the physical mechanics of a dripping tap, but not very much has been done on the sound," Dr Anurag Agarwal — from Cambridge’s Department of Engineering, who led the research — said in a statement. "But thanks to modern video and audio technology, we can finally find out exactly where the sound is coming from, which may help us to stop it."
The idea for conducting the research didn't actually burst forth from a leaky tap, however. It was actually a leaky roof dripping into a bucket that inspired the research.
Agarwal first decided to delve into this predicament after visiting a friend who had a leak in their roof. "While I was being kept awake by the sound of water falling into a bucket placed underneath the leak, I started thinking about this problem," says Agarwal. "The next day I discussed it with my friend and another visiting academic, and we were all surprised that no one had actually answered the question of what causes the sound."
Using an ultra-high-speed camera, a microphone, and hydrophone, Agarwal recorded water droplets falling into a tank of water.
Per the research, the "fluid mechanics of a water droplet hitting a liquid surface" are pretty well established. Basically, when a droplet hits the surface, it prompts the "formation of a cavity which quickly recoils due to the surface tension of the liquid." This then creates a "rising column of liquid." Due to the speed with which the cavity recoils after the droplet hits the surface, a small air bubble gets "trapped underwater."
Previous research has suggested that the "plink" sound could be caused by a number of things, like the impact of the droplet on the surface, the "resonance of the cavity," or the "underwater sound field propagating though the water surface." But, until now, no research has confirmed what the source is "experimentally."
Interestingly, Cambridge researches found that all three of these previously suggested sources are "all effectively silent."
The source of the sound is, in actual fact, the trapped air bubble.
So, how precisely do we put a stop to this truly repulsive noise?
Well, researchers found that by changing the "surface tension of the surface" by adding washing-up liquid, the sound can be stopped. You might get through an awful lot of Fairy Liquid, but at least you'll get some sleep. Either that or you could call a plumber.
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