How to Reduce Window Sound Transmission

As population density increases in urban areas, acoustics has become a vital consideration in the building industry. Demand has increased for larger windows, to increase natural light and for wonderful outdoor views, however, it often comes with unwanted exposure to the outside noise.

One of the ways to reduce noise exposure is by understanding sound and choosing the right acoustic window to reduce unwanted, intrusive urban noise.

The Construction Specifier magazine recently shared these steps to consider to reduce sound transmission.

The first step is to understand and measure the sound transmission

Sound has two main properties. Frequency, or sound vibration speed, determines the pitch of the sound and is measured in hertz (Hz). Amplitude, or sound vibration wave size, determines how loud the sound is and is measured in decibels (dB).

When it comes to sound attenuation, there are two key measurements used to calculate these properties and the amount of sound (dB at a particular frequency) that is blocked.

• Sound Transmission Class (STC) measures higher-frequency noises such as voices and barking dogs.
• Outdoor-Indoor Transmission Class (OITC) measures lower-frequency exterior noises such as airplanes and traffic.

The higher the rating, the better the sound-blocking capability.

The second step is to consider design requirements to control sound

• Air infiltration/leakage is one of the biggest factors in attenuation performance. If air can penetrate, sound can penetrate. This includes design techniques used to seal operable windows.
• Fenestration mass, the heavier the frame is the greater the sound-damping effect.
• Insulated Glass (IG) configuration, the air space created by double glazing increases the STC/OITC ratings.
• Laminated glass, the interlayers act as shock absorbers to dampen sound waves.
• Frame design, generally framing profiles, with open spaces, reduce noise transmission, creating air spaces similar to IG configurations. Thermal breaks further reduce noise vibrations through the frame.
• Glass to frame ratio, both have separate sound attenuation properties and should be paired accordingly. Other weaker materials will lessen the overall effectiveness of the unit.
• Glass resonance, glass with resonant frequencies similar to the intruding sound will amplify rather than cancel it.
• Seal tightness, the use of soft, resilient seals can decrease low-frequency sound transmission.
• Flanking, sound will find a path to transmit other than through the fenestration. Floors, walls, ceilings, and other assemblies may need to be modified.

The third step is to verify fenestration product(s) meet acoustic standards

There is no substitute for full and independent testing in an accredited lab to assess the standards required for full compliance building regulations and standards. As with any performance parameter, using a reliable methodology to obtain uniform and comparable measurements is key to comparing different products fairly and consistently.

Effective use of acoustic windows has become essential to keeping urban noise out and creating quiet interior spaces. Look for STC and OITC ratings to find the optimal levels of noise mitigation. Our acoustic window experts at St. Cloud Window can help you find the best window for your acoustic needs – request a quote today for more information.