3. Art meets science
This kinematic sculpture by Eusebio Sempere consists of a periodic array of hollow stainless-steel cylinders, each 2.9 cm in diameter, arranged on a square 10 × 10 cm lattice. In 1995 researchers at the Materials Science Institute of Madrid showed that the sculpture strongly attenuated sound waves at certain frequencies, thus providing the first experimental evidence for the existence of phononic band gaps in periodic structures.