Can Windows Reduce Sound Transmission?

Noise pollution is a real problem for tenants in office buildings, apartments, and other properties in urban environments. According to researchers, noise pollution from traffic, nearby trains or airports contributes to stress, reduced motivation, and trouble concentrating.

If your property is subjected to continuous ambient noise, you might be wondering: Is there anything I can do to dampen the sound?

One place to start is with your windows. Sound-dampening and sound-proof windows are designed to protect against ambient noise, and different types of windows are better equipped to soundproof your property. Generally, the noise-reducing abilities of your windows depend on a few factors, including glass thickness, the number of panes and air-tightness.

Ultimately, your windows can be a powerful sound-reducer. The most effective sound-dampening windows can eliminate about 95% of outside noise. Want to see how windows can reduce noise in your workplace? Here’s everything you need to know about sound-proof windows.

How Is Window Noise Reduction Measured?

New and replacement windows all have a sound transmission class (STC) rating, which is a measure of their ability to reduce exterior noise. STC ratings are one of the most common measures of sound transmission, and it’s an industry standard. If you’re interested in reducing ambient noise, you should first consider a window’s STC rating.

There is a range of ratings for the most commonly used types of windows, with STC ratings ranging from 18 to 38. A rule of thumb: the higher the STC rating, the better the window is at diminishing noise transmission. The best soundproof windows, though, these days, exceed these ratings, with STCs into the 40s and 50s.

If you have a property with existing single-pane windows, for instance, your windows are likely rated around 18-20 STC. In some cases, the STC rating may even be lower than that, depending on the year that they were installed. Double-paned windows, on the other hand, which are increasingly common, are in the STC 26-33 range. This type of window includes two layers of glazing separated by air, which maximizes the window’s noise-reducing powers.

So how much sound could potentially be blocked out by replacing the dated single-paned glass? It depends on the STC rating of the existing glass. But if your windows are old and have an STC rating in the 18-20 range, replacing them with double-paned windows can potentially reduce noise by as much as 40 percent.

How Do Windows Reduce Sound?

Looking for windows that will reduce noise transmittance? Start with the STC rating. Windows with higher STC ratings are better equipped to reduce noise. Why does higher STC rated windows do a better job of cutting sound?

Many factors can contribute to a window’s noise-stopping potential, including materials, glass thickness, glass type, and spacing. The highest-rated STC windows combine all of these factors to “soundproof” an office, which generally means reducing about 90 to 95 percent of outside noise. Read more about how windows can reduce sound transmission here.

Here are some of the factors and materials that can maximize the sound-proofing potential of a window:

• Glass Thickness – The thickness of the glass is the most critical factor in a window’s STC rating. Thicker glass cancels out more sound. And therefore, higher STC windows tend to utilize thicker glazing.
• Laminated Glass – Laminated glass is standard in hurricane-prone areas, as its much more impact resistant. But it can also contribute to a higher STC rating. Laminated glass windows feature a layer of plastic sandwiched between two layers of glass. The plastic layer helps to deaden noise, and due to its design, this type of glass is usually thicker as well.
• Spacing – The majority of commercial replacement windows are double-paned, meaning there are two layers of glass. The spacing between each sheet of glass plays a role in dampening noise. Wider spacing helps to weaken sound waves. Additionally, gas fills between panes can help to slow sound transmittance.
• Material – Frame materials can have an impact on STC rating. Typically, vinyl and wood windows perform best, as they deaden noise better than other materials. Aluminum and steel, on the other hand, tend to conduct noise more efficiently.
• Dissimilar Glass – In the majority of dual-pane windows, both panes of glass have the same thicknesses. With dissimilar glass, each pane has a different thickness. The reason: Each pane cancels out specific frequencies. One pane would block lower-frequency sounds – like a garbage truck accelerating – while the other targets higher-frequency noises, like a car horn.
• Window Type – Windows with higher glass-to-frame ratios – or windows with slimmer frames – tend to perform better. That’s why casement windows, picture windows, and curtain walls tend to achieve the highest STC ratings (especially when the glass is specifically designed for noise reduction). 

Ultimately, for maximum noise dampening, a window would need an STC rating between 40 and 50. That type of window may only be necessary for the noisiest of environments like an office in a central business district, or a property located near a train line. In many situations, a double-hung window with an STC of 26-32 might be sufficient for reducing the majority of the noise.

For information on soundproofing walls and doors, click here.

Are Triple-Pane Windows Necessary?

It only seems right that adding another layer of glass would increase a window’s sound-controlling capabilities. Triple-Pane windows tend to perform only slightly better than double-pane windows. The reason?

Triple-pane windows tend to have less spacing between each pane. The air spacing is critical in absorbing sound, and generally, the wider the gap between panes, the better the window is at canceling noise. Double-pane windows, on the other hand, maximize that noise-deadening space between the panes, and as a result, they tend to perform well in terms of noise reduction.

Ultimately, a double-pane window with different glass or laminated glass will likely compete closely with a triple-pane window. Click here for more on multi-pane windows.

Other Tips for Reducing Window Sound Transmission

Installing windows with a higher STC rating is one step you can take to diminish noise transmission. Replacing existing windows can be more costly, and there are a few steps you can take before (and, in some cases, after) replacing windows. They include:

• Repairing window seals: Existing window frames may not be adequately sealed, which is a major cause of noise transmission. Patching gaps and air leaks can help to reduce noise and diminish drafts, and it’s a more cost-effective solution than complete replacements. This is one of the first steps you should take, but it is often difficult for property managers to do one every window in their building(s).
• Using sound blocking treatments: Drapes, curtains, and blinds are available that have been designed to reduce and prevent exterior noise. For instance, one option is acoustical blankets, which are very heavy window coverings that are made from sound-absorbing materials. These block sound, but they often block natural light, as well. Other options include sound-absorbing interior shutters, window mats and, more generally, any heavy-duty fabric treatments. If you enjoy or even require the natural light for environmental purposes, or if you are growing indoor plants, then these options are often not the best.
• Installing storm windows: Storm windows are secondary windows that are mounted to the exterior or interior of a window. They effectively add another layer of glass. Commonly, they’re used to improve efficiency; the secondary layer diminishes drafts and provides a tighter seal. Additional sound reduction is a common secondary benefit of storm windows. Storm windows are more cost-effective than soundproof windows, and they can effectively reduce noise transmission by 50% or more. Like traditional windows, storm windows are available with different thickness glazing, laminates, gas fills and new panes, which can improve the window’s sound-reducing properties.

Click here for more information on choosing the best windows for reducing outside noise pollution.

Bottom Line

In all, windows are a significant source of noise transmission. The good news is that there are some easy steps you can take to reduce noise, starting with repairing seals and installing sound-reducing treatments. For better sound-proofing, though, installing new double- or triple-paned windows with high STC ratings may be necessary to block out the majority of exterior noise.

Since 1999, Aeroseal has provided property owners on the East Coast with window solutions for combating ambient noise. If you’d like more information about how we can help with window sound-proofing, contact us today for a free consultation.