A square chain is a unit of area measurement that is now considered obsolete and not commonly used. It was historically used in some English-speaking countries, including the United States and the United Kingdom, as part of the older system of land measurement.
One square chain is equal to an area of 10 square rods, or 484 square yards. In terms of square meters, one square chain is approximately equal to 404.68564224 square meters (m²).
The square chain was often used in land surveys and property descriptions in the past, but it has been largely replaced by the more standardized metric and imperial systems of measurement. In modern times, square meters and square feet are the more commonly used units for measuring land area.
A "sabin" is a unit used to measure the sound absorption of a material or surface. It quantifies the effectiveness of a material in reducing sound reflections within a room or space. The sabin is named after Wallace Clement Sabine, an American physicist who made significant contributions to the study of architectural acoustics.
One sabin is equivalent to one square foot (approximately 0.0929 square meters) of perfectly sound-absorbing material. In other words, if a material has a sound absorption of 1 sabin per square foot, it means that it absorbs all sound energy that strikes it, and none is reflected.
Architects, acoustical engineers, and designers use the sabin as a measurement to assess and improve the acoustic properties of rooms, such as concert halls, theaters, recording studios, and offices. By selecting materials with known sound absorption coefficients and calculating the total sabin value for a space, they can optimize the acoustic environment to reduce unwanted echoes and noise.