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What is STC Rating?
STC stands for Sound Transmission Class. STC ratings are numbers that describe how well something stops airborne sound from traveling through it. They are used as the standard in the United States for soundproofing materials. Other countries use the SRI, or Sound Reduction Index.
How is STC Rating measured?
STC ratings must be measured by a professional, like an acoustical consultant. The process typically looks like this:
- Create a controlled environment with two rooms separated by a wall
- Install the product between the rooms
- Transmit a range of frequencies through the product
- Measure how much of the transmission is lost
This is a scientific process that requires specialized equipment in the hands of a knowledgeable professional. It’s not something that you can DIY if you want your results to be taken seriously.
Is STC Rating Reliable?
Yes – STC ratings for windows, doors, walls, and other materials provide a good comparison of their capability to block sound. Importantly, the number you see on an STC chart may not reflect your actual experience if you install something like an STC rated window yourself.
Remember that the sound transmission class is calculated in a controlled environment by a skilled professional. This means that the installation of the product is perfect – ideal in every way. The actual effect that any given product has on noise may depend on many things, like:
- Quality of materials
- Quality of installation
- How well the rest of the room is sealed or soundproofed
- Whether there are alternate paths into the room
- The size and shape of the room
- The climate, both inside and outside
- The frequency of the noise
For more clarity, look at STC ratings as an approximate comparison. Furthermore, hire a professional for the installation of such products – you’ll get much closer to the listed sound transmission class. That’s why at Sun and Sound Windows we make and install our own soundproof window inserts.
STC Rating Chart of Popular Products
The following chart shows average STC ratings for generic barriers (i.e. interior walls) as well as a selection of branded products.
| Barrier | STC Rating |
|---|---|
| Soundproof curtains | 23 |
| Single pane window | 27 |
| Double pane window | 29 |
| Pella lifestyle series double-hung window | 31 |
| Interior wall (drywall, no insulation) | 33 |
| Exterior wall (drywall with fiberglass insulation) | 39 |
| Andersen windows E-Series Double Laminated fixed window | 40 |
| Exterior hollow concrete wall (6 inches) | 46 |
| Sun and Sound Windows soundproof window inserts over double pane window | 48 |
| Exterior hollow concrete wall (8 inches, drywall inside) | 54 |
| Acoustical Surfaces Studio 8 interior window | 58 |
Improve Your Window STC Ratings
If you’re dissatisfied with your windows and want to block more noise from entering your home, you’re in the right place. Get some rough measurements of your window(s) and fill out our online estimate form – it only takes a few minutes. You’re one step closer to enjoying peace and quiet.
