Observations: Physics tricks could make for one-way soundproofing

Observations: Physics tricks could make for one-way soundproofing: "By stacking layers of nonlinear materials along with ordinary linear layers in an asymmetric fashion, the researchers have calculated, a wave would be able to pass through in one direction but would almost completely bounce off when it arrives from the other direction. The one-way bias isn't universal, however—the researchers note that each particular implementation would have a sweet spot of wave amplitudes and frequencies for which it would work best."