I can't find it now, but there was a youtube video of a guy building a fence to block road noise by building interlocking pottery 'bricks' with cavities that would absorb certain frequencies
helmholtz resonators, well known in acoustical engineering, also known as beer bottles and people, enough of which can significantly alter an acoustical signal.
the idea of useing specific shapes to redirect sound is new to me, but parralels how reflected coulor can work in birds and insects, where two mechanisms are employed, pigments that simply absorb(heat up) with some frequencys and reflect others, and then mechanical structures that are tuned to capture some frequencys and reflect others, producing the iridesent effects that are so attractive.
recent work has revealed that silk and artificial cloth's, can convert sound into heat quite effectivly, and other work where transparent plastic is put as an extra sound absorbing layer in windows
