Scientists find a great practical use for ping pong balls: ScienceAlert

A new study proves that if you find yourself bothered by low-frequency urban sounds — like traffic, airplanes, and other city sounds — the humble ping-pong ball offers a low-cost way to block them out.

It is known that the noise is low frequency Bad for our health, but it is also difficult to block. It often comes from multiple directions, and is not blocked by walls and structures in the same way that high-frequency noise is.

To combat low-frequency noise, researchers from the University of Lille in France and the National Technical University of Athens in Greece used ping-pong balls. Helmholtz resonators; Enclosures specially designed to accommodate specific sound frequencies.

The team experimented with different arrays of ping pong balls. (Sabat et al., Journal of Applied Physics2023)

Named after the German physicist who made the original Helmholtz resonator, Hermann von Helmholtz, the devices consist of an empty chamber, like a ping-pong ball, with a small opening.

“Ping pong balls are common everyday objects, found in large numbers all over the world,” He says Physicist Robin Sabat from the University of Lille.

“Our motivation was to use these easily accessible objects to create a low-frequency dielectric plate structure. Thus, ping pong balls offer an economical alternative to acoustic insulators in terms of low cost and potential recyclability.”

As the name suggests, Helmholtz resonators work through it echoAnd matching the vibrations of sound waves in order to absorb them. The size of the container and the size of the aperture determine the frequency of sound that the resonator can absorb.

While Helmholtz resonators It has been widely studied Previously, researchers wanted to look at how they work and interact when combined to form an acoustic acoustic surface; Materials specially designed to handle sound waves in different ways.

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This combination or pairing has been shown to increase the number of resonant frequencies absorbed by the acoustic surface of the ping pong ball. In other words, more sound can be blocked by using multiple Helmholtz resonators together.

“The Helmholtz resonator has the unique ability to accurately pick up ambient sound waves at their natural frequency and can be represented as cavities connected to their environment via a narrow neck.” He says Sabat.

“The originality of the work was to consider the coupling effect between two resonators, which gives rise to a resonant frequency.”

Using a combination of mathematical modeling and actual experiment, the researchers demonstrated the way multiple HRs interact with each other to control which sound frequencies are blocked.

Although there has not been any large-scale field testing of ping pong balls that block certain sounds, there is potential for these ubiquitous and affordable objects to be used to protect against noise pollution — and more.

“The potential of this breakthrough surface extends beyond sound insulation.” He says Sabat. “It can be expanded to achieve different functions similar to other metasurfaces.”

“These functions include audio focus, unconventional sound reflection, sound transmission processing, and more.”

The research was published in Journal of Applied Physics.

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