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STC Doors

Sound Transmission Doors are becoming more prevalent in today’s world. We are putting more people in smaller spaces which causes a need for Sound doors.  The chart below gives out the STC ratings for common doors.  I noted on this chart where a typical hollow core metal door & a typical particleboard core wood door would give without any extra gasketing.
Sound Transmission Class
STC
Performance
Description
50-60
Excellent
Loud sounds heard faintly or not at all
40-50
Very Good
Loud speech heard faintly
35-40
Good
Loud speech heard but hardly intelligible
30-35
Fair
Loud speech understood fairly well
Typical wood door
25-30
Poor
Normal speech understood easily and distinctly
Typical hollow core door
20-25
Very Poor
Low speech audible
  Typical applications for STC doors: Schools (Band or Music Rooms; perhaps cafeteria doors), performance venues, conference rooms, lecture halls, auditoriums  and consulting rooms.  As with fire rated doors, these doors are tested as an assembly (door, frame, hardware including gasketing), so if that particular configuration has not been tested then the STC rating would not be available.  It is important to note that sound doors are only as good as the gasketing surrounding it.  Automatic door bottoms are important.  These come in 3 types surface, full mortise and half mortise. The most effective is the surface applied as this leaves the most mass to stop the sound.
The figure below demonstrates a typical STC 39 door.  You see the decimal level of noise coming to the door and the amount leaving the door.
As a general rule things to know about STC doors when specifying:
1.            Stay away from glass in the doors if you can.  If you cannot; stick with 3 x 33 narrow lites.
2.            Sidelights are also very limited and most likely will not meet the STC requirement.
3.            As with sidelights, pairs are limited in what will meet the STC requirement.
4.            Fire ratings can be a conflict – it is very possible that a fire rated door cannot meet the STC requirements.  In all of the cases I have seen of this the fire rating has taken precedence.
5.            Make sure that the gasketing and automatic door bottoms are properly installed. These will give the greatest insurance that the door performs as desired.
As always call us if you need us.
debbie
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