The sound of dripping water from the faucet
Recently scientists have solved the puzzle behind one of the most recognizable and annoying household sounds: the sound of dripping water. Crucially, they also found an easy solution to stop it, and most of us have found that solution in our kitchens. Dripping faucet scientists have solved the puzzle behind one of the most recognizable and annoying household sounds: the sound of dripping water. Crucially, they also found an easy solution to stop it, and most of us have found that solution in our kitchens. Using ultrafast cameras and modern audio capture techniques, researchers at the University of Cambridge have discovered that the “plink, plink” sound produced when a water drop strikes the surface of a liquid is not caused by the drop itself, but by the vibration of small bubbles trapped beneath the surface of the water. The bubbles force the water surface to vibrate itself, driving the airborne sound like a piston. In addition, the researchers found that changing the surface tension, such as adding dish soap, could block the sound. The findings were published in the journal Scientific Reports. Although people have been awakened for generations to the sound of dripping water from a leaky faucet or roof, the exact source of the sound has never been known. Dr Anurag Agarwal of the University of Cambridge’s Department of Engineering, who led the study, said: “A lot has been done on the physics of dripping taps, but not much has been done on the sound. “But thanks to modern video and audio technology, we are finally able to pinpoint the source of the sound, which may help us stop it. "Agarwal is the head of the acoustics lab and a researcher at Emmanuel College, who first decided to investigate the problem when he visited a friend who had a small leak in his roof. Agarwal’s study investigated the acoustics and aerodynamics of aerospace, household appliances and biomedical applications. He said: When I woke up to the sound of falling water, I started thinking about it. “The next day, I discussed the issue with my friend and another visiting scholar, and we were both surprised that no one really answered the reason for the voice. "Agarwal collaborated with Dr. Peter Jordan from the University of Poitiers (who spent time in Cambridge through an Emmanuel College fellowship) and senior Sam Phillips on an experiment to study the problem. Their device uses an ultra-fast camera, microphone and hydrophone to record water droplets that fall into the tank. Water droplets have been a source of curiosity to the scientific community for more than a century: the earliest photos of water droplets striking were published in 1908, and since then scientists have struggled to find the source of the sound. The hydrodynamics of water droplets striking a liquid surface is well known: when a water drop strikes a surface, it causes the formation of a cavity, which bounces back quickly due to the surface tension of the liquid, causing the liquid column to rise. The cavity rebounded too quickly after the droplet hit, causing small air bubbles to become trapped underwater. Previous studies have hypothesized that the “Prink” sound is caused by the impact itself, cavity resonance or an underwater sound field propagating through the water, but this cannot be confirmed experimentally. Researchers at the University of Cambridge found in their experiments that, somewhat counter-intuitively, the initial splash, the formation of a cavity and the ejection of liquid were all effectively silenced. The source of the sound is the intercepted bubbles. Phillips, now a PhD student in the engineering department, said: “Using high-speed cameras and high-sensitivity microphones, we were able to directly observe the oscillations of bubbles for the first time, showing that bubbles are the main driver of underwater sound and the unique ‘plink’ sound on board. “However, the sound in the air is not just an underwater sound field that propagates to the surface, as previously thought, In order for the “base” to be significant, the trapped air bubbles need to be near the bottom of the cavity caused by the impact of the fall. The bubbles then drive the oscillation of the water surface at the bottom of the cavity, like a piston sending sound waves into the air. This is a more effective mechanism through which underwater bubbles drive the airborne sound field than was previously suggested. According to the researchers, while the study was conducted out of pure curiosity, the results could be used to develop more effective ways to measure rainfall, or to develop convincing synthetic sounds for water droplets in games or movies, which have yet to be realized.