Why a Dripping Faucet Makes That Maddening 'Plink' Sound

In most cases, calling a professional is the best option when dealing with a stubborn faucet leak. With the right tools and knowledge, the problem isn't that difficult to solve. But when every other thought you have is interrupted by that incessant "plink" noise, even a few hours spent waiting for the plumber can feel like an eternity. A team of scientists recently looked at the mechanics that make that sound so annoying, and they've come up with a quick fix you can use to silence it before tackling the source.

The researchers from the University of Cambridge recently published their findings in the journal Scientific Reports. To get to the bottom of the annoying acoustics, they recorded a leaky faucet using a microphone, a hydrophone, and ultra-high-speed cameras. “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,” lead researcher Anurag Agarwal said in a press release. “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.”

They found that the unmistakable "plink" comes not from the water droplet itself, but from an air bubble trapped beneath it. When a drop of water hits something, a cavity forms inside it. This cavity immediately recoils, creating a water column that splashes away from the surface that was hit. The cavity recoils so quickly that it leaves a small air bubble beneath the water.

Scientists already knew the physics, but until now it was unclear which part of the equation produces the dripping noise. The University of Cambridge team observed that it's not the impact of the droplet, the creation of the cavity, or the upward splash of water that make the sound: It's the air bubble, which vibrates and pushes sound waves through the air in a way that's uniquely grating to the ears.

The researchers were also able to identify a way to neutralize this effect without any fancy equipment. Just add some liquid soap to the bottom of the sink to change the surface tension of the water each time a droplet splashes. This slight adjustment is enough to stop the air bubble from forming and quiet the sound.

The constant noise keeping you up at all hours of the night isn't the only reason leaky taps are a pain. According to the Environmental Protection Agency, Americans lose 1 trillion gallons of water a year to leaks. Every year, the EPA runs Fix a Leak Week, a campaign aimed at getting homeowners to catch all the wasteful leaks on their property—not just the ones within hearing distance.