FIELD SOUND TRANSMISSION CLASS (FSTC) OVERVIEW
The FSTC is a single number rating for walls and floor-ceiling structures installed in a building. The rating is derived from values of field transmission loss in accordance with ASTM E-413. Typical values of FSTC range from 45 - 55.
To calculate FSTC:
Background measurements are taken in the source and receiving room.
A speaker is set up in a corner of the source room away from the wall to be tested. Pointing the speaker toward the corner reduces the direct field from the speaker in the source room.
Sound levels measurements are taken at several positions in the source and receiving room.
Depending on size and geometry of the source room, the speaker may need to be moved the the sound level measurements repeated.
Reverberation times are measured in the receiving room.
The FSTC is calculated per ASTM E-413.