Sabin (unit)

In acoustics, the sabin (or more precisely the square foot sabin) is a unit of sound absorption, used for expressing the total effective absorption for the interior of a room. Sound absorption can be expressed in terms of the percentage of energy absorbed compared with the percentage reflected. It can also be expressed as a coefficient, with a value of 1.00 representing a material which absorbs 100% of the energy, and a value of 0.00 meaning all the sound is reflected.^[1]

The concept of a unit for absorption was first suggested by American physicist Wallace Clement Sabine, the founder of the field of architectural acoustics. He defined the "open-window unit" as the absorption of 1 square foot (0.093 m²) of open window.^[1] The unit was renamed the sabin after Sabine, and it is now defined as "the absorption due to unit area of a totally absorbent surface".^[1]

Sabins may be calculated with either imperial or metric units. One square foot of 100% absorbing material has a value of one imperial sabin, and 1 square metre of 100% absorbing material has a value of one metric sabin.

The total absorption A in metric sabins for a room containing many types of surface is given by $${\displaystyle A=S_{1}\alpha _{1}+S_{2}\alpha _{2}+\ldots +S_{n}\alpha _{n}=\sum S_{i}\alpha _{i},}$$ where S₁, S₂, ..., S_n are the areas of the surfaces in the room (in m²), and α₁, α₂, ..., α_n are the absorption coefficients of the surfaces.

Sabins are used in calculating the reverberation time of concert halls, lecture theatres, and recording studios.^[2]