Noise Reduction

A sound solution to effective noise reduction

Reducing unwanted noise

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 Viridian VLam Hush™ range of laminated glass is specifically developed to do just that.

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 Table 1). The design exercise is then to construct the wall in order to reduce the external noise level to that desired in the room – where the external noise is known from measurements and the internal noise level is recommended (ISO 140). For glass, this would involve subtracting the Rw value of the external noise level from the internal level to determine the type of glass required.

The source of the noise may be higher at certain frequencies. For example, 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. Example: For a living room on a busy street, the required glass Rw value is 75dB (busy street) – 40dB (living room) = 35dB (glass). Refer to Table 2 for glass options.

Sound reduction index

Rw is the weighted sound reduction in decibels which incorporates a correction for the ear’s response. Every 10dB is perceived as twice as loud, so that a 20dB reduction would reduce the noise by four times.

Common solutions

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 a glass thickness but generally occurs at higher frequencies such as those associated with aircraft noise.

• 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 100mm to 200mm 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