3rd March 2023
A Sound Solution for Effective Noise Reduction
Whether it’s from traffic, aircraft, trains, factories or even neighbours, unwanted noise is a nuisance but it can be reduced with the right selection of glass. The VLam™ Hush and ComfortHush™ range of laminated glass is specifically developed to do just that.
Reduce the Transmission of Noise
There are three things that occur when sound waves encounter a window:
1. They may be reflected away, causing little concern to those inside the building
2. They may be absorbed through dampening and dissipated, causing little concern to those inside the building
3. What isn't reflected or absorbed is transmitted through the window by vibration or air leakage
Ordinary glass can vibrate at the same frequency as the noise source, allowing sound to penetrate through the window. VLam™ Hush and ComfortHush™ includes a special 3-layer laminate that has been specifically engineered to reduce vibration, making it effective in reducing urban noise.
Addressing a Noise Problem
Typically the weakest point in a home is the windows. Installing windows with good acoustic performance needs to be supported with the careful selection and insulation of walls, floors and roof materials to enhance the overall acoustic performance of your home. It is essential to ensure that all other paths in the exterior of the building have also been sealed.
Designing to Solve a Noise Problem
There are generally three components to be considered when solving a noise problem. These are the external noise, the noise reduction of the wall (windows and glazing) and the resulting noise in the room. The process of design requires that the external noise level is determined by measurement and the desired internal noise level is decided (Refer to table 1).
The source of the noise may be higher at certain frequencies. Typically, suburban traffic noise is a low frequency noise, while aircraft produce a high frequency noise.
A detailed solution would involve measuring the nature and intensity of the offending sound and choosing a glass product which would reduce the intensity sufficiently at all frequencies.
It should be noted that glass is only one part of the room and all other components must be assessed as well.
Reduce Air Leakage
Cracks, crevices and even the smallest gaps will greatly reduce the performance of windows by providing opportunities for sound to travel through. It is critical that VLam™ Hush and ComfortHush™ are used in combination with a carefully selected window frame that is well sealed to significantly reduce air leakage. Many window manufacturers make and test windows designed to improve acoustic performance and energy efficiency. It is important these windows are professionally installed to reduce air leakage by ensuring a good seal between the exterior of the window and the wall it is being installed into.
Sound Reduction Index
The Weighted Sound Reduction Index (Rw) is a number used to rate the effectiveness of a soundproofing system or material. Increasing the Rw by one translates to a reduction of approximately 1db in noise level. Therefore, the higher the Rw number, the better a sound insulator it will be.
The coincidence dip is the frequency at which the glass panel vibrates in unison with the frequency of the incident sound pressure waves. The result is the sound insulation properties of glass being strongly reduced at this specific frequency.
Thick glass – the greater the thickness the better the noise reduction for low frequencies such as traffic noise. However, standard glass has a coincidence dip when the glass vibrates at the same frequency as the noise source. This is dependent on glass thickness but generally occurs at higher frequencies.
Laminated glass – the interlayer is particularly effective at dampening which provides superior sound reduction over the same thickness monolithic glass. Further, the dampening effect of laminated glass reduces the coincidence dip at these higher frequencies and therefore is a solution for aircraft and voice noise.
Double glazing – standard insulating glass units do not provide good noise reduction. For insulating glass units to be effective, an air gap of 50mm to 100mm needs to be provided. However, the incorporation of one or two panels of laminated glass, a glass of differing thickness or VLam™ Hush into the unit provides excellent results.