>"The researchers designed a device made of an array of circular piezoelectric resonators arranged in repeating hexagons, like a honeycomb lattice, and bonded t

>"The researchers designed a device made of an array of circular piezoelectric resonators arranged in repeating hexagons, like a honeycomb lattice, and bonded to a thin disk of polylactic acid. They then connected this to external circuits, which provide a time-modulated signal that breaks time-reversal symmetry." [...] >"In a breakthrough for physics and engineering, researchers from the Photonics Initiative at the Advanced Science Research Center at The Graduate Center, CUNY (CUNY ASRC) and from Georgia Tech have presented the first demonstration of topological order based on time modulations. This advancement allows the researchers to propagate sound waves along the boundaries of topological metamaterials without the risk of waves traveling backwards or being thwarted by material defects." My interpretation of this is that these researchers may have invented the analogue of an electrical diode -- but for sound, that is, a sound diode. This sound diode then, may pave the way to a greater understanding of diodes (both electrical and sound) in general, and possibly pave the way towards a future sound transistor, that is, a transistor where a little bit of sound (as pitch, analogue of electrical voltage) acts as either a switch or a regulator for a whole spectrum of sound (analogue of electrical current). Of course, all of that is highly speculative, and I'll settle for a sound diode -- for now! I applaud the work of these researchers!