An ancient theatre filters out low-frequency background noise. The ancient Greek theatre of the Asklepieion of Epidaurus, built mostly during the 4th century B.C. and now a World Heritage Site, is renowned for its extraordinary acoustics. Researchers have figured out that the arrangement of the stepped rows of seats are perfectly shaped to act as an acoustic filter, suppressing low-frequency background noise while passing on the high frequencies of performers' voices.
"This is a story of how the impossible became possible. How, for centuries, scientists were absolutely sure that solids (as well as decorative patterns like tiling and quilts) could only have certain symmetries - such as square, hexagonal and triangular - and that most symmetries, including five-fold symmetry in the plane and icosahedral symmetry in three dimensions (the symmetry of a soccer ball), were strictly forbidden. Then, about twenty years ago, a new kind of pattern, known as a "quasicrystal," was envisaged that shatters the symmetry restrictions and allows for an infinite number of new patterns and structures that had never been seen before, suggesting a whole new class of materials...."
Now only if I can get a pair of headphones with good base!
