Acoustic performance of windows in heavyweight walls.
For this type of construction the windows are the dominant paths for sound transmission from outside the building to inside.

Sound and noise
Sound is the human perception of vibrations in the air around us. Noise is unwanted sound.
Noise can be annoying, can interfere with the enjoyment of everyday activities and in the extreme can be harmful. It may also be beneficial at low levels where it can serve to mask sounds and aid privacy.

Sound Characteristics
Sound originates when air is vibrated. It travels outwards from the source as pressure waves just as ripples travel outwards on a still pond.
A “pure” sound is characterised by its frequency and its sound pressure level.

Frequency determines the pitch of the sound. It is the number of vibrations that occur i
n one second and is measured in Hertz (Hz). The distance between consecutive waves is the wavelength measured in metres.

Sound pressure level (SPL) is a measure of the peak pressure created as a sound pressure wave passes. Sound pressure levels are expressed in decibels (dB), a logarithmic scale.

Decibels
Table 1 below shows typical sound pressure levels in dB.

Table 1. Sound pressure levels

General principles
In general the achieved noise reduction to external noise is controlled by the weakest component in the envelope. If the sound
insulation of the solid or opaque wall of a facade is at least 15 dB higher than that of the glazing, noise transfer through the wall can be ignored and transmission through the windows, and other openings, alone may be considered. This is most common as typical single brick walls have an Rm of 45 dB and cavity brick walls of better than 50 dB.

Whilst the window will be the weakest component in a heavy weight wall, the presence of openings in or around a window may completely dominate its performance.

Glazing performance
Data on the acoustic performance of glazing is widely available but needs to be used with caution. The acoustic data in the public domain tends to relate to the performance of a standard pane size of 1480mm x 1230mm fitted and sealed directly to the acoustic test chamber. In practice, if a window is of similar dimensions the framing normally has only a nominal effect on the acoustic performance if all joints are tight fitting. However, if there is a marked increase in the pane size or rigidity of the frame, a significant worsening of the acoustic performance is likely. Thus specifiers and architects are cautioned against taking acoustic data for standard pane sizes and applying them to large elements of a building’s facade.

Simple tips
Sound can easily enter a home through exterior windows. There are many ways that you can alter a window in order to improve sound protection in your home.

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