Noise is not equal to noise. Contrary to appearances, much smaller influence on our health has an intensive but short sound in comparison with long-lasting ones, which are less noticeable but affecting the nervous system. On the top of the list of “acoustically dangerous” things are schools, offices and houses. Particularly uncomfortable may be noise in a work place – according to researches, heaviness of open space sounds in the office makes that the efficiency of employees decreases by at least a half, and repeatedly by even 66 per cent in comparison with work in silence.
Acoustic insulation
Due to the harmfulness of staying in places, where an excessive noise dominates (as well as, though to a lesser extent, on account of building conservation, their construction and materials) a lot of norms were introduced, for instance, PN-B-02151-3:1999, which regulates acoustic directives in a precise way. Their guidelines should be taken into consideration on all stages of building the structure and known by contractors of a building process – from designers, constructors to representatives of a construction supervision. It is worth to think about the acoustic comfort on the stage of a project designing. Regulations which inform us about the necessity of protection against external noise, coming from installations, devices, airborne and strike noise; we may also classify conversation noise between employees as burdensome sound. Therefore, we should remember that the influence on a resultant insulation has nearly every its element, especially windows, doors and facades.
The most important parameter considering noise issue is acoustic insulation. It defines damages in transmission and applies to a difference between sound level outside or inside the building, from which a noise is generated and sound level in a room, in which this sound is received. The PN-87/B-02151/02 “Structural acoustics. Protection against structure noise in buildings. Acceptable values of a sound level in buildings” norm informs us about expectations concerning acceptable sound levels. According to it, a maximum sound level totals 40 dB in case of meeting halls and 35 dB for rooms intended to headwork, which requires a high level of concentration. Important information is also delivered to us by PN-B-02151-3:1999 norm. If a noise level raises concerns, we should instruct the execution of an acoustic measurement test – compartments’ insulation should reach values described in the regulation of the infrastructure minister considering technical conditions, which buildings and their locations should meet. It may turn out that the reason for uncomfortable acoustic environment in the interior are windows with a poor acoustic insulation, which do not allow penetration of external sounds.
Important parameters
In initial tests and declarations of windows, doors and facades performance, Rw (C; Ctr) indicator is defined, where Rw indicates weighted index of an acoustic insulation, whereas C and Ctr are adaptation rates. Such record allows to compare acoustic properties of this type in many different countries of the European Union and their useage with the assessment of acoustic properties of the compartment according to the local legislation – explains Doctor of Engineering Andrzej Polijaniuk, director for product and marketing in the Schüco International Poland. In Poland, to this type of assessment the single number rates are applied, that is RA1 = Rw + C and RA2 = Rw + Ctr., where C rate concerns sounds with the advantage of high frequency (road traffic on motorways and freeways with the speed of over 80 km/h, rail traffic of high and medium speed, or air traffic in short distance), whereas Ctr rate of low frequency sounds (traffic in the city, rail traffic of low speed or, for instance, disco music). Although, Rw rate is not authoritative and it has not obtained since 1999 in the Vistula, it constitutes an important supportive function. A mentioned Rw (C; Ctr) rate informs us whether a certain construction together with glazing meets better or worse the planned conditions. It is designated to masters of these compartments in laboratory tests. In case of serious international system suppliers, such as Schüco International, the selection of proper construction is relatively easy, these companies have hundreds of acoustic tests of their systems with nearly all available glass types – prompts the expert.
We should not forget that many complex factors have an impact on the window acoustic insulation, even though we may associate the problem only with a glass type. A window is a composite compartment, composed of a number of structural elements with various acoustic properties – says Andrzej Polijaniuk. Although this glass occupies the largest window surface, in spite of appearances, a pane, even with the best acoustic parameters, does not guarantee a maximum protection. Currently, there are glass sets with very good acoustic properties available on the market. However, it does not mean that a whole window has the same parameter. Except for this, a shape of the window, geometric dimensions and construction system, matter. Compartments with higher acoustic insulation require specialized installation, that is the one which may help in the protection against password.
Finally, it is worth to remember that even a pane with best parameters may be set in a wall in a properly hermetic way, so as it may perform its function. The lack of precision, inaccuracy, wrong materials and leaving cracks cause that the noise, in spite of very good parameters of the window, will pervade into the apartment. Thereupon, during the planning of compartments with a certain insulation, some unplanned but possible improprieties have to be taken into consideration – the value of correction is minimum 2 dB.