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What do NIC, RW and STC mean in decibel units?
The United States (according to the American material testing standard ASTWE-90, E-4 13) adopts the sound insulation grade, that is, STC (sound transmission grade) grade. STC is a simple numerical scale. It is equal to Rw in most cases. Can be used interchangeably.

STC is measured for a single component under laboratory conditions. For the actual field sound insulation performance, it is more accurate to use noise isolation NIC. NIC measures the total attenuation of sound from one room to another, regardless of the sound propagation path.

STC and NIC systems have the same experimental process and method, which are used to evaluate the ability of sound insulation components to block people's speech. The evaluation and measurement methods are not accurate for the isolation between rooms and bedrooms, which may be annoying sources of machine noise, aircraft noise and non-verbal noise. However, STC and NIC provide good guidance for comparing different components of airborne acoustic noise in multi-family houses.

For example, the STC of a laminated insulating glass (specification: 3mm glass +0.76PVB film +3mm glass+12mm air layer +6mm glass) is 39, and the STC is 42 when the air layer thickness is multiplied by 25 mm.