Professor - Department of Physics

University of North Texas

Title: "Nonreciprocal acoustics"

Abstract:

Communication via wave signals assumes that at the point of reception the level of signal is sufficiently strong. The signal does not necessarily come directly from the emitter; it may suffer from multiple reflections and diffraction, forming a pattern of the signal intensity in space. This pattern, being quite complicated in presence of scatterers, nevertheless, satisfies a general principle of reciprocity. According to this principle if the emitter and receiver switch their positions, the signal coming to the new position of the receiver remains the same. This originates from the time-reversal symmetry of the wave equation, thus, reciprocity is equally valid for electromagnetic and sound waves. However, it is easy to get one-directional transmission of electric current by including a diode into electrical circuit, thus, violating the reciprocity. It is much more difficult to break time-reversion symmetry for sound. In this talk the current progress toward nonreciprocal acoustics and the perspectives of having an acoustic diode will be discussed.

*Refreshments will be served before the colloquium*