Physicists explain how sound can travel through a vacuum

Sound waves pass through a vacuum gap. Credit: Zhuoran Geng and Ilari Maasilta

The iconic movie alien He once claimed: “In space, no one hears you scream.” However, physicists Zhuoran Geng and Ilari Maasilta of the Center for Nanoscience at Jyväskylä University, Finland, disagree. Their recent research indicates that, under certain conditions, sound can indeed be transmitted powerfully through a vacuum.

Their findings, recently published in the journal Communication Physics, revealing that in certain scenarios, sound waves can “pass” through a vacuum gap between two solid bodies, provided these bodies are piezoelectric. These particular materials generate an electrical response when exposed to sound waves or vibrations. Given that an electric field can exist in a vacuum, it can effectively transmit these sound waves.

The condition is that the gap size is smaller than the wavelength of the sound wave. This effect works not only in the range of acoustic frequencies (Hz-kHz), but also in ultrasonic (MHz) and ultrasonic frequencies (GHz), as long as the vacuum gap becomes smaller with increasing frequencies.

In most cases the effect is negligible, but we also found situations, where the full wave energy jumps through the vacuum with 100% efficiency, without any reflections. As such, this phenomenon could find applications in microelectromechanical components (MEMS, smartphone technology) and in heat control, says Professor Ilari Maselta of the Center for Nanoscience at the University of Jyväskylä.

Reference: “Full Tunneling of Acoustic Waves Between Piezoelectric Crystals” By Zhuoran Geng and Ilari J. Maasilta, July 14, 2023, Available here. Communication Physics.
DOI: 10.1038/s42005-023-01293-y

The study was funded by the Academy of Finland and the European Union’s Horizon 2020 programme.