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History of the Sound Transmission Class

Sound Transmission Class (STC) is a concrete way of measuring how well something reduces sound. When selecting windows and doors, understanding STC values is the best way to determine the best products for your soundproof studio.

What Is a Sound Transmission Class?

Sound Transmission Class (STC) is a system of rating how well a material reduces airborne sound and represents the approximate decibel reduction in noise. The system is commonly used in the United States to measure doors, windows and walls. In the STC rating system, the higher the rating, the greater the material’s ability to reduce sound.

Why Were Sound Transmission Classes Invented?

Increased problems with noise control in multi-family dwellings and a trend in lightweight structures spurred an interest in sound insulation in the 1960’s. Other single-value ratings were previously used, until they were replaced by the STC value system. The concept for the STC system was based on other sound rating systems in Europe.

How Do We Currently Measure STC?

STC rating is measured through a test in accordance with ASTM E90 (Standard Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions). The test is performed by testing sound reduction at a set number of standard frequencies from 125 Hz to 4000 Hz. After plotting the values on a graph, the data is analyzed using ASTM E413 (Classification for Rating Sound Insulation).

What Are Desirable STC Values for a Soundproof Studio?

STC rating for a standard dual pane window is 26 – 32, depending on the glass thickness and the amount of air space between the glass, while most walls have an STC of 43-48. For significant noise reduction, the STC rating needs to be greater than 40.

At Soundproof Studios, our products make it possible to achieve STC ratings in the 60’s. All of our StudioMax™ Window and Door products hold world records for their high STC values. Check out our line of soundproof studio products or download the lab test results to see the STC values for our recording studio windows and recording studio doors.

Call Soundproof Studios at 877-438-7843 to request your free estimate!

sound transmission class in a soundproof studio

Sidney Levy, Construction Calculations Manual 2012
Raymond D. Berendt and George £. Winzer, Sound Insulation of Wall, Floor, and Door Constructions 1964
Acoustical Assembly Guide, National Gypsum