How Does Soundproof Glass Work?

thick double sheet of soundproof glass seen from the corner
  • Advanced

If you purchased the windows for your house, chances are you purchased them for their ability to keep the outside air from affecting the room's ambient air. In other words, you probably chose them for their energy-efficient qualities. After a few years, though, you might find your neighborhood is expanding, becoming more populated, more active, and definitely noisier and at all hours of the day or night.

If your windows are relatively new or are still in excellent condition, replacing them with a better soundproof alternative may not make financial sense. Energy efficiency is probably still the priority, which you may have well covered. Nonetheless, there could be a solution to the noise outside from a different field of physics.

In every home, the walls, roofs, floors, and windows smother noises and sound coming from outside at different levels by obstructing a certain percentage of sound waves from intruding. Due to its hardness, a single pane of glass, especially if it's thin, happens to be a pretty good conductor to sound waves. There are, however, three main factors that can increase a window's ability to block sounds and increase the STC rating.

Thickness—The thicker the glass pane is, the less sound can go through.

Number of Panes—Adding more panes with an air space in-between will also block more sound the wider the air space gap is between the panes.

Lamination—Using a laminated glass composed of two sheets of glass with a sheet of plastic sandwiched in the middle and glued and cured as one will reduce noise transmission significantly.

panels of double paned glass with plastic centers

Soundproof Glass Ratings

Like other construction materials, glass can be given a sound transmission class rating (STC), a numerical value of its ability to reduce sound. Tthe higher the number, the more a partition inhibits audio from passing through. A basic single-pane window has an average STC rating of 27, and an average dual-pane window rates between 26 and 32.

A four-point STC improvement can cause a clearly perceptible change in your home’s acoustics, while a 10-point improvement can reduce sound by 50 percent. Soundproof windows offer ratings of at least 45 to mid-50s, blocking up to 95% of noises.

STC was originally developed to measure the sound transmission between interior walls and is the most widely used system as of this writing. While not as well known as STC, OITC or Outdoor-Indoor Transmission Class is a newer rating system for measuring the sound transmission of low- and mid-frequency noises through exterior walls.

Ways to Increase the STC of Your Windows

1. Double-Paned Glass

The most common soundproofing method is by using double-paned glass, which logically will cut out more noise than single-paned. However, compared to the other two types of soundproof glass, this is the most ineffective.

stack of double paned glass panels

2. Thick Glass

Whether you want a soundproof glass wall or windows, increase the glass thickness as thick glass does not vibrate like thin glass. As a result, the level of sound penetrating the room is considerably reduced especially if it is from a glass density twice the size of the normal one for maximum benefits.

3. Laminated Glass

The plastic lamination between the two glass panes making the glass firmer and less subject to vibrations. The plastic lamination makes it more difficult for the noise to go through the glass, besides making the window sturdier. There are two ways to optimize the use of laminated glass.

Additional Pane—An “aftermarket” option for noise-reducing windows is an additional laminated glass pane that gets put onto your existing windows. There are plenty of companies that offer this service at a range of prices. Ultimately though, this option is cheaper than getting a new insert window or doing a full-frame replacement. Once the laminated glass is put on, however, you can no longer open your window.

Replacement—The next step up is a retrofit replacement with laminated soundproof glass where a new insulated glass unit gets put into your existing frames, and because the laminated glass is already in the sealed unit, the functionality of your window isn’t affected. This offers an important improvement in energy performance and sound transfer.