Acoustic Diode (image) American Institute of Physics Caption This is a schematic illustration of "acoustic diode" made of a zero refractive-index medium (ZIM) prism, which only allows the acoustic waves comes from the left ("positive incidence") to pass but blocks the waves from right ("negative incidence"). Credit Urbana/ B. Liang Usage Restrictions This image may be used only with appropriate caption or 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.