Sound radiation pressure

Sound radiation pressure (also: Acoustic radiation pressure ) is a physical phenomenon that has been known since the 1850s and was first described theoretically by Rayleigh . As early as the late 1830s and early 1840s, Herz and Mende discussed the sound radiation pressure in liquids.

The sound radiation pressure describes the pressure difference averaged over time compared to the normal pressure of the medium when the sound field hits other media (obstacles). Since a measurable force is exerted on the obstacle due to the pressure, it is also referred to as a sound radiation force .

Development of the sound radiation pressure

The cause of the resulting force is the different behavior of the air particles when they are pushed off and sucked into the vibration generator in the course of a period, which occurs at a high frequency, depending on the medium. If the medium cannot expand sufficiently quickly when it is sucked back, additional particles flow in laterally. The repulsion moves the individual air particle in the sound beam a little further away than it can be sucked back, creating a flow directed away from the ultrasound source (so-called quartz wind ). When it hits an obstacle, this results in a force known as sound radiation pressure.

Another approach explains the sound radiation force theoretically with the help of a sound radiation voltage tensor . This method makes it possible to draw conclusions about the power emitted by the sound source from the measurable sound radiation force using theoretical formulas.

Current research

By superimposing the sound radiation pressure of several ultrasonic sources, zones with increased pressure can be generated in three-dimensional space, which can be felt like a real object. Currently (around 2016), research can generate a total force of 16 mN (0.0016 kp ) over a region of 20 mm in diameter  .

Applications

• Ultrasonic fogger. A liquid medium is atomized by the turbulence arising from the sound radiation pressure at the interface.

literature

• F. Borgnis, On the physics of sound radiation pressure in: Zeitschrift für Physik, Volume 134, Number 3, June 1953 Berlin / Heidelberg Volume 134, Number 3 / June 1953, pages 363-376
• Acoustic radiation pressure produced by a beam of sound J. Acoust. Soc. At the. Volume 72, Issue 6, pp. 1673-1687 (December 1982)
• A general theory of Rayleigh and Langevin radiation pressures. J Acoust Soc Jpn E (2000)

Individual evidence

1. ^ RT Beyer: Radiation pressure — the history of a mislabeled tensor. In: The Journal of the Acoustical Society of America, 1978
2. ↑ The sound radiation pressure in liquids . Hertz, G. and Mende, H. in: Zeitschrift für Physik 05/1939, Volume 114, Issue 5-6, pp. 354-367
3. ↑ Dr. Torsten Hehl, Jan Bärtle: Ultrasound . Experiment instructions, Physikalisches Institut der Universität Tübingen 2003, p. 138.
4. ↑ Sound radiation pressure in air ( Memento of the original from February 20, 2011 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. , Experimental set-up Faculty of Physics, Univ. Regensburg. 
5. ↑ Ultrasonic power measurement . Physikalisch-Technische Bundesanstalt, Working Group 1.62 - Ultrasound.
6. ↑ "Airborne Ultrasound Tactile Display" in "Pervasive Haptics", Springer, 2016
7. ↑ Experimental arrangement for the ultrasonic whirlpool, Physikalisches Institut, Univ. Stuttgart ( Memento from November 17, 2008 in the Internet Archive )