ABCs of Noise Control Materials

Noise Absorption

Sound absorbers are soft, porous, open-celled materials such as foam sheets or fiberglass blankets and baffles that reduce the reflection of sound waves. Their sound absorption efficiency is rated by a "NRC" number - Noice Reduction Coefficient*. The HIGHER the NRC rating, the more EFFICIENT the product is at absorbing noise.

*NRC is a sound absorption rating. It measures a percentage of how much sound will not be reflected back from where it came. Based on a range from .05 to 1.0, where a NRC of 1.0 means that all the sound energy that hits that product passes through it and does not "bounce" back to its source. A NRC of .60 would reflect 40% of the sound back to the source and let 60% of the noise pass through it.

Noise Barrier

Noise Barriers combine mass, flexibility and limpness to block noise from transmitting from one area to another. Flexible mass-loaded vinyl sheeting has replaced thin lead sheets as the noise barrier of choice. Noise Barriers are rated by a "STC" number - Sound Transmission Classification. The HIGHER the STC rating**, the more EFFICIENT the product is at blocking noise.

**STC Sound Transmission Class : Single-number rating of airborne sound insulation of a partition, derived by fitting a reference rating curve to the sound transmission loss values measured for the 16 contiguous 1/3 octave frequency bands with nominal mid-band frequencies of 125 Hz to 4000 Hz inclusive, by a standard method. The standard method typically used is ASTM Standard E90. This test is valid for single homogenous layers, multiple layers, or complete assemblies. A higher STC rating typically represents a better ability to stop noise, frequency notwithstanding.

Noise Composites

Acoustical Composites are products that combine both Noise Barrier & Sound Absorber materials. Typically, they olffer the most significant overall noice reduction. Acoustical Composites are rated in both "NRC"* and "STC"** numbers. Sound Seal uses composite materials as Panels, Acoustical pipe & duct Lagging or in Acoustical Curtain Systems.

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