Noise Reduction Glass
Sound originates from something that vibrates which generates changes in air pressure. Frequency is used to refer to the number of vibrations or changes in air pressure per second. The value given is usually expressed as hertz (Hz) (i.e. 750Hz). Different sounds produce different frequencies. The Intensity or Loudness of a sound is of most concern to people. The loudness of a sound is rated as Decibels or ‘dB’. There are two fundamental considerations that come into play when measuring the reduction of sound through windows and selecting a glass for sound insulation:
- Sound Transmission Loss (STL) – indicates the effectiveness of a window or wall in reducing exterior sounds. In determining the ability of a window or wall in reducing outdoor sounds such as traffic noises, engineers usually figure STL in the frequency ranges of 100- 3150Hz (UK) or 125-4000Hz (USA). The STL is measured in decibels (dB) and thus the greater the STL value the better the glazing is for reducing sound
- Sound Transmission Class (STC) – indicates the reduction of sound provided by an interior wall. This rating applies to interior partitions, walls, ceilings and floors, but not to exterior walls. In terms of glass this means office partitions, viewing windows for radio / TV stations and similar applications. The STC value is a number rating that is designed to correlate the effectiveness of sound insulation of elements against sounds normally sourced inside buildings (i.e. speech, typewriters). Before exploring the sound reduction capabilities of glass it is important to establish the fact that the best sound reducing glass cannot do its job if air leaks or cracks allow sound to travel around the glass
As a general rule, increasing mass will improve sound insulation. Brick and concrete walls have stronger sound insulating values because they are of greater mass when compared to glass.
But because we need glass to see through, to provide natural daylight and to enhance a buildings look and appeal, the need for greater sound control when using glass becomes more important.
- Sound reduction will improve with increased glass thickness due to the greater mass involved
- Sound reduction will improve with the use of laminated glass due to the vibration dampening effect of the PVB interlayer. Laminated glass is particularly effective for interior partitions as it reduces the ‘coincidence dip’ attributed to monolithic glass in the 1000-2000Hz range, a range attributed to the human voice. The optimum PVB interlayer thickness for sound reducing laminated glass is 1.14mm but 0.38mm will generally suffice. Multi-laminates combine the mass effect of solid glass with the dampening effect of the interlayer for superior sound reduction
- Sound reduction will improve with the use of glass/ airspace combinations, but the performance is critically dependent upon the width of the airspace. An airspace of 100mm is generally regarded as a minimum for reasonable benefits at medium to high frequencies. The optimum airspace is about 300mm, but for practical purposes 200mm is more acceptable.
- Sound reduction will improve with the use of ORIGIN OZ Glacoustic™, a laminated glass that uses a specially developed sound control interlayer to give high-quality acoustic glazing. Compared to float glass of the same thickness, an improvement of 5dB in the sound insulation value can be achieved.
|Colour Range||Any combination of colour and glass clarity from clear, extra clear, tinted, patterned|
|Thickness (Min – Max)||6mm – 10.36mm|
|Air Space (Min – Max)||100mm – 300mm|
|Panel Size (Min – Max)||(100mm x 100mm) – (5000mm x 2600mm)|
Noise reduction compared to 3mm float (in STL):
|Glass Thickness (mm)||Reduction (Db)|
|6.0||3 – Barely Noticeable|
|6.38||5 – Clearly Noticeable|
|6.76||7 – Clearly Noticeable|
|10.38||11 – Halving of Original Noise|
NOTE – Glass is just one component in the window and door system. Suppliers of these complete products should have accredited testing to determine noise reduction ratings for the complete window assembly, not just glass.