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What are STC Ratings and Why Are They Important?

What is an STC Rating?

Sound Transmission Class ratings, commonly referred to as an STC rating, is an integer rating that details how well a building partition reduces airborne sound waves. In the US, it is widely used to rate interior partitions, such as demountable walls and/or glass walls, ceilings/floors, doors, windows and exterior wall configurations.

Why are STC Ratings Important?

Both noise distractions and privacy are two of the most common complaints that are made against a multitude of workplace layouts, especially in an open office. And there are many factors that contribute to the noise problem.

For example, having exposed ceilings and concrete floors (which is what IR Group has) may provide a specific type of design aesthetic, but it may also pose a problem since there are limited barriers to soften the sound waves.

Have you ever walked past an enclosed office or room and were still able to hear the conversation(s) that were taking place in that specific space? Sure, the sound may have been mildly muted but the key point to take away here is the fact that you (an individual on the outside of the space) could clearly make out the conversation taking place on the inside of that space. Now factor in privacy concerns. Maybe that conversation was meant to be confidential? Or factor in the sound happening outside of that enclosed space. Are you able to conduct a meeting or focus without being distracted by what’s going outside your door?

Oddly, this situation seems to be common among many of our clients, which is exactly why the STC ratings are an important influence on workplace design.

Choosing a product with a higher STC rating, in most cases will result in better sound control. Products with STC ratings that are lower will most likely be less “sound controlling.” Check out the chart below to get an idea of what each rating may sound like.

STC partition ratings taken from: "Noise Control in Buildings: A Practical Guide for Architects and Engineers"; Cyril M. Harris, 1994

What is the ideal STC rating?

The ideal STC rating depends on the application and outside factors that may contribute any interference. For private offices, an STC rating in the 40’s may be more common. Conference rooms and other meeting spaces may be ok with an STC rating in the high 30’s, but again the outside factors such as an open floor plan may require a higher STC rating.

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