Low-frequency noise, ubiquitous in cities, roadways, and airports, can cause earaches, respiratory impairment, and irritation. Pingpong balls, typically hollow plastic balls, can assist in absorbing this noise, which is difficult to prevent due to its diverse sources and shapes. The researchers describe an acoustic metasurface that uses pingpong balls as Helmholtz resonators to provide low-frequency sound insulation that is affordable but effective.
Pingpong balls, readily available common objects, were utilized to construct a low-frequency insulating panel structure, providing an affordable, low-cost, and recyclable alternative to acoustic insulators specifically built for sound wave manipulation. The Helmholtz resonator is distinguished by its ability to precisely catch ambient sound waves at their natural frequency. It can be represented as cavities connected to their surroundings by a thin neck. The work was unique because it considered the coupling effect between two resonators, resulting in two resonance frequencies.
More resonant frequencies meant that the device could absorb more sound. Following the success of two connected resonators, the researchers added more until their device resembled a square sheet of punctured pingpong balls, thus doubling the number of resonant frequencies that could be absorbed. The researchers were able to vary the acoustic properties of the metasurface by adjusting the number of balls, holes, and hole size, demonstrating that it is possible to construct a sound absorption panel without using expensive materials.
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