What is sound?
Sound is a variation of pressure (in the air, in the water, etc.) the human ear can perceive.  The number of pressure variations in one second is called the sound frequency and is measured in Hertz (Hz). The distance between two subsequent crests of waves is called  wave length. [Do you remember the stone thrown into the pond? The concept is the same].

The Decibel (dB)
The most interesting parameter of sound is the dimension or amplitude of pressure variations, as these are perceived as noise.
Since the human ear can cope with very high sound pressures, expressed in Pascal (Pa), conventionally the decibel (dB) scale is employed to avoid using huge numbers. The dB scale is a logarithmic system using the threshold of hearing of 20.000 Pa as the basic level, defined 0 dB. By multiplying the sound pressure by 10, we merely add 20 dB to the level in dB. 200.000 Pa correspond to 20 dB, 2.000.000 Pa are equal to 40 dB and so on. Therefore, a small variation in dB actually means an important variation in the sound pressure, or in other words, much more noise. For example: a pneumatic hammer produces a sound pressure of approximately 105 dB. Two identical hammers produce 108 dB pressure.

In the light of above statements, let us now explain how particularly noise absorbing window glass is obtained:

The glass is used in layers with one or two PVB (polyvinyl butyrate) sheets plus an air or inert gas (Argon) cushion between one layer and the other- the bigger the cushion, the better the sound absorption- and then again glass in layers. These window glasses, with different thicknesses of layers and air cushion, allow for a relevant sound reduction by up to 50 dB, which is really an excellent result.

This is the reason why we work in close contact with our glass suppliers. Windows manufactured by Stenfis are always adaptable to customer requirements and technologically advanced in all their components.

Technical information
Please notice: the theoretic calculation of the acoustic insulation can be made only for those windows having passed  the air tightness test with  at least a class 3 score.

All windows made by Stenfis, in whatever combination (in size, sash number, types, etc.) have obtained at least class 3 in the air tightness test. For all types of Stenfis windows it is therefore possible to calculate the acoustic insulation.

With reference to the rule iso 140-3¹ and by using the specific IGU tables, which the rule mentioned tolerates limitedly to  Rw values (noise insulation capacity factor) below 39 dB, with a glass of 4/9/4mm. thickness, the Rw value has been calculated to correspond to 32 dB (value valid for windows up  to 2,70 m² total surface) thus fully complying to the rule.

In those cases, where a better coefficient is required (Rw ≥ 39 dB), we at Stenfis are ready to have specific laboratory tests carried out to determine the exact acoustic insulation.


¹Rule iso 140 – 3rd part
Acoustics. Measurement of the acoustic insulation in buildings or building elements. Measurement of the acoustic insulation of building elements per air way in the laboratory.