Recently the name of the field sound transmission class rating system which was known as FSTC has been changed to apparent sound transmission class (ASTC).
What does this mean, to you, the end user?
The simple answer is: not very much!
The test is still conducted using the same basic methodology, meaning that the equipment and testing process is largely the same.
So be aware that test results that used to say FSTC now say ASTC.
ASTM E336 – 14
Standard Test Method for Measurement of Airborne Sound Attenuation between Rooms in Buildings