A unit of sound absorption used in acoustical engineering. One sabin is the sound absorption of one square foot (or one square meter — a metric sabin) of a perfectly absorbing surface–such as an open window. Typical non-perfect absorbers are thus have values in the tenths of a Sabin range. The sound absorption of a wall or some other surface is the area of the surface, in square feet, multiplied by a coefficient that depends on the material of the surface and on the frequency of the sound. These coefficients are carefully measured and tabulated. The unit honors Wallace Sabine, an American physicist and Harvard University professor who founded the systematic study of acoustics around 1895. Regarded as the father of the science of architectural acoustics, Sabine used this unit, which he called the open window unit (owu), as early as 1911.