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Impact Noise Rating (INR)

Obsolete rating system for floor-ceiling construction in isolating impact noise. INR ratings can be converted to approximate IIC ratings by adding 51 points; however, a variation of 1 or 2 points may occur.

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Impact Strength

The energy required to fracture a specimen when struck with a rapidly applied load.

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Impact Noise

Sound generated by impact on the floor or other parts of a building that is carried through the building.

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Impact Insulation Class (IIC)

Single-number rating used to compare and evaluate the performance of floor-ceiling constructions in isolating impact noise. The advantages of this rating system are positive values and the correlation with Sound Transmission Class (STC) values -- both providing approximately equal isolation at a particular value. The IIC rating is used by building agencies for specifying minimum sound-control performance of assemblies in residential construction.

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Impact Insulation Class

An index of the extent to which a floor assembly transmits impact noise from a room above to the room below.

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Illuminance

The density of luminous power in lumens per a specified area.

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Impurity

An unintended substance present in a material/mixture as manufactured that was not an intentionally used substance in the production of the material/mixture. It may originate from the starting materials or be the result of secondary or incomplete reactions during the manufacturing process. For example, a chemical substance as supplied in commerce that is 99.0% pure is a mixture of the pure chemical substance and 1.0% of impurities. https://healthymaterialslab.org/tool-guides/hml-resources

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Impact Test

A test for determining the resistance of a specimen fracture from a high-velocity blow.

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In Situ

Undisturbed soil.

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Incandescence

The emission of visible light produced by heating.

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Index

The interest rate or adjustment standard that determines the changes in monthly payments for an adjustable rate loan.

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Independent Footings

Footings supporting a single structural element, such as a column.

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Infiltration

The passage of air from indoors to outdoors and vice versa; term is usually associated with drafts from cracks, seams or holes in buildings. The process by which water soaks into the ground. Also called Percolation.