A structure for absorbing wave energy, particularly acoustic wave energy, which includes a first essentially planar surface against which wave energy is directed and a second essentially planar surface generally parallel to and spaced from the first surface. Wedge-shaped elements of sound-absorbing material...http://www.google.com.au/patents/US4477505?utm_source=gb-gplus-sharePatent US4477505 - Structure for absorbing acoustic and other wave energy
