Many designers and architects of modern offices choose glass office environments for their beauty, daylighting abilities and the way they foster teamwork. Such office spaces are typically partitioned by a mix of glass sliding doors and fixed glass panels. Threfore, one issue that often arises in such environments is architectural acoustics or sound control.
Glass does not control sound in the same manner as drywall, wood, brick, etc., allowing voices and other sounds to carry. Moreover, this can create a lack of privacy for those working in the space. For this reason, the American Institute of Architects (AIA) has created noise standards for commercial and residential spaces, including one called Sound Transmission Class (STC).
This post will discuss how the STC ratings are performed and how they are typically manipulated, as well as Klein’s approach to veracity and transparency in their in-house STC ratings.
Sound Transmission Class (STC)
The American Institute of Architects sets standards for sound control and architectural acoustics for residential and commercial spaces. One of their ratings is the Sound Transmission Class (STC), which measures a material’s ability to block airborne sound.
In office buildings, they require an STC rating of anywhere from 37 to 60. To put this into context, these are the STC levels at which a sound is audible through a partition:
| 25 | Normal speech is clearly audible and understandable |
| 30 | Normal speech is hard to understand, loud speech is clearly audible |
| 35 | Loud speech is audible, but not clear |
| 40 | Loud speech can be heard, but is not understandable |
| 45 | Loud speech is barely audible |
| 50 | Very loud sounds, like musical instruments, are audible |
| 60 | Very Loud music is barely audible; power tools are audible |
| 70 | Power tools are faintly heard |
| 75+ | Most sounds are completely inaudible |
Common partitions are materials like drywall, insulation, wood, sound dampeners, and glass. Each material has different ratings – but the ratings cannot be added to achieve a higher STC.
In performing its own in-house tests, Klein USA has learned that different types of fixed and sliding glass panels test different for noise ratings. For example, double-glazed panels will obtain a better result than single-glazed, and both of these will test higher than a sliding door, which has gaps that noise can pass through. Below is an example of how Klein’s Panoramic Sliding Glass Door System helps control sound.
Is a Higher STC Rating Really Better for Architectural Acoustics?
The general rule of thumb is that higher STC ratings are better. However, a product with a higher STC rating does not necessarily mean it is more soundproof for all types of noise, especially noises that are very common around the work place.
The STC only measures frequencies down to 125 Hz. This can be misleading because most sound complaints result from noise sources below 125 Hz. Here are a few examples of noises below this level:
- Music
- Theaters
- Traffic
- Aircraft
- Heavy equipment
In addition, the STC rating only determines how a material performs in the lab at optimum conditions, not in the field in real-life usage. As noted above, certain factors degrade performance of glass sliding doors and panels; such as HVAC ductwork, inadequate door and window construction and even the type of gasket used. All of these gaps allow sound to penetrate and effect performance.
Architectural Acoustics Considerations for Choosing Glass Partitions
Most glass partition manufacturers test ‘best case scenario’ situations to be able to achieve and advertise the highest STC rating. For example, most only test fixed, double-glazed, and laminated panels, as opposed to testing a real-world mix of fixed and sliding glass panes of different thicknesses, sizes, and make-ups.
When considering a provider of interior glass walls and doors, it’s important to know what configuration the company used for the foundation of their sound testing. The only way your project will achieve the same results is with the exact same construction as was tested by the manufacturer. Threfore, consider what limitations your site may have that keep you from achieving these numbers (i.e; budget, dimensions, aesthetics, etc.)
When Klein analyzes glass partitions, we take in consideration the real-world use of the panels, which is most often a combination of fixed panels and sliding panels. This will result in a lower sound rating – but a more realistic representation of usage. We also state in our test results which panels and glazes were tested, and whether sound dampeners or other materials were used.
While no sliding glass door system can be totally soundproof due to sound passing above and below the panels and between fixed and sliding panels, Klein’s Panoramic Sliding Glass Door System has the following options to reduce sound.
- Double glazing
- Double fixed glass up to 5/8”
- Recessed tracks
- Minimal separation between fixed and sliding panels
- Isolating edge seals to ensure a secure enclosure
To view the architectural acoustic testing results of the Panoramic system, please contact us.
When choosing materials for your next project, don’t simply choose the fixed partition or sliding glass wall with the highest STC rating. Instead, look for the company that is transparent in its testing methods and results to achieve the most realistic understanding of how your design will perform in the real world.
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