The ability to steer electromagnetic waves around regions of space has revolutionised optics and sparked a global interest in Harry Potter-style invisibility cloaks. But it isn't only photons that are the target of these devices.
Various engineers and physicists have also begun work on acoustic versions that steer sound. In particular, a few groups have begun to think about how this technology might be used to steer seismic waves round buildings. The idea would be to protect high value buildings such as nuclear power stations or airports. We examined just such a proposal last year.