How Good Is An Acoustical STC Rating?

HOW GOOD IS AN STC RATING?

Use the following chart to get a rough idea what various STC levels mean in terms of privacy afforded. Note that this is only a very rough guide

STC PRIVACY AFFORDED
25 Normal speech easily understood
30 Normal speech audible, but unintelligible
35 Loud speech understood
40 Loud speech audible, but unintelligible
45 Loud speech barely audible
50 Shouting barely audible
55 Shouting not audible

Source: U.S. Dept. of Commerce / National Bureau of Standards. Handbook 119, July, 1976: Quieting: A Practical Guide to Noise Control; Page 61.
STC’s OF FAMILIAR CONSTRUCTIONS

Listed below are some typical building items and materials, to give you an idea how the typical operable or accordion partition compares.

STC CONSTRUCTION
18 Hollow-metal door without seals
22 Solid wood door without seals
26 1/4" plate glass
32 1/2" plate glass
38 1/2" drywall on wood studs, both sides
41 4" painted concrete block wall
42 5/8" drywall on steel studs, both sides
46 8" hollow concrete block
48 12" painted concrete block wall
50 Double 5/8" drywall on steel studs, insulated
53 12" poured solid concrete wall

Acoustical Field Testing of Operable Walls

Preparation for Acoustical Field Testing


The following guidelines are to insure an operable partition system is ready for field testing.


Things to look for prior to a test;

After you set up the operable partition, look for the obvious leaks first. This can be accomplished by turning out the lights in the room you are in and visually inspecting all of the panel joints (vertical and horizontal).

If light leaks are detected, reset or repair the operable partition and repeat the step above.

Turn on a radio or any electronic equipment which can generate a lot of noise. This noise level should be high enough to drown out any outside noise such as air conditioning, high intensity lighting or kitchen noise, etc.


Check the following areas:

· Plenum barrier, visually inspect that the barrier is present and complete. By complete, I mean, that the barrier is constructed from the top of the track to the bottom of the roof deck above.
· Vertical joints of all panels
· Top seals, the full length of the opening.
· Bottom seals, the full length of the opening.
· Joint at the dual bulb seal.
· Joint at the lever closure jamb.
· Area above the sweep seal of the lever closure jamb assembly.
· Area below the sweep seal of the lever closure jamb assembly.
· Area at any special condition; Pocket door top header, wall jamb, multiple meeting post, inset pass door perimeter, etc.


Correct any deficiencies and repeat the steps above until no leaks are detected.



Now, the operable partition system is ready for testing.