Sound transmission loss studies help to determine the amount of noise reduction that is achieved by an object, material or construction assembly as sound travels through it. The result of a Sound Transmission loss test is represented with an STC number. The STC rating is and average of the decibel loss for frequencies 125 Hz to 4000 Hz. The higher the STC number, the better the material or assembly is at blocking sound.
When a product or construction assembly is installed in a specific location, the STC may be influenced by other variables. Measurements from an in-field test may be required to validate whether the object or construction is providing its intended acoustical performance. The main test standard for in-field measurements of STC is the E336, a standard test method for measurement of airborne sound attenuation between rooms in building.
The results of testing for sound transmission loss may be used to qualify building assemblies to meet building code requirements or meet other standards for safety and privacy like OSHA and HIPAA.