
Time modulation-based propogation of sound waves on topological metamaterials - bookofjoe
https://phys.org/news/2020-07-scientists-major-breakthrough.html
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peter_d_sherman
>"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!

