The classic movie “Alien” was once advertised with the slogan “In space no one can hear you scream”. Conversely, physicists Zhuoran Geng and Ilari Maasilta from the Center for Nanoscience at the University of Jyväskylä in Finland have shown that in certain situations sound can be strongly transmitted through the vacuum region.

In a recent article published by Communication PhysicsThey show that in some cases, if the materials in question are piezoelectric, a sound wave can jump through a vacuum gap between two layers or “tunnel” completely. Vibrations (sound waves) in such materials also cause an electrical response and can transmit sound waves as the electric field can exist in vacuum.

The requirement is that the size of the gap is smaller than the wavelength of the sound wave. This effect works not only in the audio frequency range (Hz–kHz), but also in ultrasonic (MHz) and hypersonic (GHz) frequencies, because with increasing frequencies the vacuum gap gets smaller.

“In most cases the effect is small, but we have also found cases where all the energy of the wave bounces in vacuum with 100% efficiency and without any reflections. Thus, this phenomenon may find application in microelectromechanical components (MEMS, smartphone technology) and temperature control,” says Jyväskylä University Nanoscience Center Professor Ilari Maasilta. Source