First Nonreciprocal Acoustic Circulator (image) University of Texas at Austin Caption A circulator for sound. The arrows represent acoustic signals flowing through the device (diameter: ~20 centimeters), which circulates sound in a nonreciprocal fashion: Signals can flow from left to top, from top to right, and from right to left, but not in the opposite directions. This creates one-way communication channels for sound, allowing listeners to hear but not be heard in return. Credit Erik Zumalt, Cockrell School of Engineering, UT Austin. Usage Restrictions Science requires that this cover image is used intact and with the accompanying caption and credit. Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.