Sound waves can leap across vacuum gaps, physicists find

Contrary to the famous saying from the movie “Alien” that “In space, no one can hear you scream,” researchers Zhuoran Geng and Ilari Maasilta from the University of Jyväskylä, Finland, have recently demonstrated an intriguing phenomenon. They’ve shown that under specific circumstances, sound can actually traverse a vacuum gap between two solid materials.

Their findings, detailed in a recent article in Communications Physics, reveal that when dealing with piezoelectric materials—ones that convert vibrations (sound waves) into an electrical response—sound waves can leap across a vacuum region. This is possible because an electric field is viable within a vacuum, enabling the transmission of sound waves.

For this effect to occur, the size of the gap must be smaller than the wavelength of the sound wave. Astonishingly, this phenomenon extends beyond just audible frequencies (Hz–kHz); it also functions in ultrasound (MHz) and hypersound (GHz) frequencies, provided the vacuum gap scales down as frequencies rise.

Professor Ilari Maasilta, who conducted the study at the Nanoscience Center, emphasizes that while this effect is generally subtle, there are instances where the complete energy of the sound wave can leap across the vacuum gap with utmost efficiency—no reflections. This discovery holds intriguing potential, potentially impacting areas like microelectromechanical components (MEMS) found in smartphone technology, as well as applications related to heat control.

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