Case Study: Commercial Office Space

In order to show just how effective SoundTITE Windows are, Buddy Rousell contracted HFP Acoustical Consultants Inc. to test SoundTITE Windows in a commercial office space. Here are their results:

 

We estimated the Sound Transmission Class (STC) and Outdoor-Indoor Transmission Class (OITC) performance of the various assemblies. Please note that this testing is not in accordance with ASTM standards. However, I believe the results are close to what would be measured in the lab. Here is the methodology used to estimate STC and OITC:

1. We began by looking up the sound transmission loss (TL) values for ¼-inch plate glass (test results are widely available). Quarter-inch glass is the existing glazing system.
2. The exterior levels were estimated by adding the TL values to the measured interior sound levels.
3. In a room with SoundTITE treatment, the measured interior level is subtracted from the estimated exterior sound level. This gives the estimated TL values for the SoundTITE treated system.
4. Using the estimated TL values the STC and OITC are calculated in the standard way.

To summarize our testing procedure:

1. Two adjacent rooms of the same size, same interior finishes, same exterior glass area, and (assumed) same exterior noise exposure were selected. The multi-lane Beltway 8 (North Belt) runs east-west north of the building and the exposed wall faces north. The two rooms are labeled West and East.
2. Two sound level meters measured the sound levels simultaneously in the two rooms. The sound level meters were set up to record the average sound level every 10 seconds for a time length of five minutes.
3. The possible window configurations:
   1. Existing ¼-inch glass only.
   2. Existing glass + one SoundTITE ¼-inch pane spaced 2 inches from the existing glass.
   3. Existing glass + one SoundTITE ¼-inch pane spaced 4 inches from the existing glass.

Here is a summary of the tests (ST = SoundTITE ¼” optical grade acrylic pane):

West East
Test #1 no ST no ST
Test #2 no ST one ST at 2”
Test #3 no ST one ST at 4”
Test #4 no ST no ST
Test #5 one ST at 2” no ST
Test #6 one ST at 4” no ST

Here are our estimates of the STC and OITC values of the tested assemblies:
STC OITC
Existing + ST at 2” 39 28
Existing + ST at 4” 40 31

The following shows the calculations to estimate the STC and OITC. NOTE: Normally in STC testing, room acoustics should be accounted for and factored out. However, since the acoustics of the rooms really did not change from test to test, only the differences were recorded and compared to the laboratory tested ¼-inch glass values. In that way, errors due to room acoustics were avoided. In the other six pages, graphs of the received sound levels in the two rooms are presented. Note that they are not in numerical order, but arranged so that like pairs of tests are together:

Test #1 and Test #4 – both rooms existing glass only
Test #2 and Test #5 – compare ST @ 2” with existing glass
Test #3 and Test #6 – compare ST @ 4” with existing glass