Sound is a physical phenomenon that requires a medium to propagate. But what happens if sound has to travel through an ideal vacuum where there are no particles capable of vibrating? Two physicists from the University of Jyväskylä in Finland, Juoran Geng and Ilari Maasilta, have found the answer to this question and presented the first rigorous proof of complete acoustic tunneling in a vacuum.
To achieve such tunneling, the scientists needed two piezoelectric materials capable of turning motion into voltage and vice versa. They placed these materials at a certain distance from each other, which was smaller than the wavelength of sound, so that the sound wave could jump through this space.
A perfect vacuum should not support the transmission of sound, as there are no particles in it that can vibrate. However, scientists have found that piezoelectric crystals can vibrate with electric fields, even in a vacuum. These crystals convert mechanical energy into electrical energy and vice versa. Thus, if a sound wave causes mechanical stress in one crystal, it will create an electric field that can be converted back to mechanical energy by another crystal. In this way, sound can tunnel through a vacuum.
This effect also scales with frequency. Even ultrasonic and hypersonic frequencies can tunnel through vacuum if the distance between crystals corresponds to the wavelength of sound.
The discovery of Geng and Maasilta is of great importance not only for the study of the physics of sound, but also for other fields of science. This phenomenon is similar to the quantum mechanical tunneling effect and can help scientists in the study of quantum informatics and other quantum phenomena.
Geng and Maasilta’s study was published in the journal Communications Physics, and they believe their discovery could find applications in microelectromechanical components and heat control.