Long-term exposure to low-frequency noise can cause many health problems, but the solution may be found in an unexpected object, a ping-pong ball. Conventionally thought of as the plastic balls that speed through the air during a fast-speed game of table tennis, with a few changes, ping-pong balls can help absorb the city noise.
Low-frequency noise is everywhere in cities, near roads, and by airports. Though potentially heard as background in the acoustic (声学的) landscape, it can lead to earaches, breathing problems and other long-term harmful effects. Because it is produced by a range of sources and is less affected by structures than higher-frequency sound, low-frequency noise can be challenging to avoid.
In Journal of Applied Physics, researchers from the University of Lille and the National Technical University of Athens describe an acoustic metasurface (超表面) that uses ping-pong balls to prevent sound passing through.
“Ping-pong balls are well-known, everyday objects, present in large numbers all over the world,” said author Robine Sabat. “Our motivation was to use these easily accessible objects to create a low-frequency soundproof panel structure. Ping-pong balls therefore present a suitable alternative to sound insulators.”
Acoustic metasurfaces are materials specially engineered to handle sound waves. This metasurface uses ping-pong balls with small holes, acting as Helmholtz resonators (共振器). More resonant frequencies meant the device was able to absorb more sound. At the success of two coupled resonators, the researchers added more, until their device looked like a square sheet of ping-pong balls covered with holes, multiplying the number of resonant frequencies that could be absorbed.
By adjusting the number of balls, number of holes, and hole sizes, the researchers could change the metasurface’s acoustic properties, proving it is possible to design a sound absorption panel without expensive materials.
“The potential of this metasurface extends beyond sound absorption,” said Sabat. “It can be broadened to achieve various functions similar to other metasurfaces. These functionalities include sound focusing, unconventional sound reflection and more.”
12. What makes low-frequency noise hard to avoid?
A.Its dull background. | B.Its covering range. |
C.Its various sources. | D.Its surrounding structures. |
13. What does the underlined word “insulators” in paragraph 4 probably mean?
A.Sources. | B.Levels. | C.Effects. | D.Barriers. |
14. What is an advantage of the newly developed metasurface?
A.It costs little to make. | B.It has light weight. |
C.It is convenient to use. | D.It is environmentally friendly. |
15. What can be the best title for the text?
A.Low-frequency Noise Can Cause Diseases |
B.Ping-pong Balls Function Well as Sound Absorbers |
C.Acoustic Metasurface Can Address Noise Problem |
D.Ping-pong Balls Show Potential in Many Research Fields |