A team of researchers has produced a record-shattering underwater sound with an intensity that eclipses that of a rocket launch. The intensity was equivalent to directing the electrical power of an entire city onto a single square meter, resulting in sound pressures above 270 decibels. The team, which included researchers from the Department of Energy’s SLAC National Accelerator Laboratory, published their findings on April 10 in Physical Review Fluids.
Using the Linac Coherent Light Source (LCLS), SLAC’s X-ray laser, the researchers blasted tiny jets of water with short pulses of powerful X-rays. They learned that when the X-ray laser hit the jet, it vaporized the water around it and produced a shockwave. As this shockwave traveled through the jet, it created copies of itself, which formed a “shockwave train” that alternated between high and low pressures. Once the intensity of underwater sound crosses a certain threshold, the water breaks apart into small vapor-filled bubbles that immediately collapse. The pressure created by the shockwaves was just below this breaking point, suggesting it was at the limit of how loud sound can get underwater.
Image: After blasting tiny jets of water with an X-ray laser, researchers watched left- and right-moving trains of shockwaves travel away from microbubble filled regions.
Credit: Claudiu Stan/Rutgers University Newark