In relation to the guideline “Støj fra veje” (Noise from roads), a new thing in Danish legislation, requirements in Denmark have been made that a fixed noise level limit for traffic-noise will have to be met indoor with open windows opened to an opening area of 0.35 m2. With a moderately/high outdoor noise level from traffic, this cannot be met with a traditional window in open position, but requires special noise reducing window solutions. With further requirements also set for windows on indoor noise from trains and companies, Window solutions with good sound properties have been under much experimentation. Useful in connection with facade restoration or replacement of windows, the standard could be well implemented in this project.
Danish Examples
Plenum Windows
Ordinary windows in an open position have low sound insulation and for that reason are not sufficient to meet the high Danish standards for indoor noise level. Plenum windows are Alternatives to ordinary open windows which have wide-ranging sound insulation but can retain natural lighting through diverse dimensions, absorption material and structural additions such as external solutions. Considered an optimised air supply window, the plenum window was developed with a focus on sound insulation for low frequencies in contrast to previously developed solutions, perforated casings were tuned to dampen the low frequency part of the spectrum.
Horizontal Plenum
Much like top hung plenum windows, the horizontal plenum solution resembles an elongated plenum chamber normally used in duct silencing purpose is introduced to act as a double-layer window. The outer later is a push open window and the inner window is a sliding window which can be adjusted to align with or offset to the opening outer layer window. By aligning the sliding window with its opened counterpart, the horizontal plenum gives maximum airflow whilst opening both windows at a staggered position offers the better noise reduction whilst allowing an air gap between the two windows to form such that natural ventilation is possible under an appropriate outdoor wind condition.
External Attenuators
The development of external attenuators describes an “ordinary window” with an added external solution. The solution in this case reduces noise from the exterior sources in existing properties to allow existing residences to meet higher standards of noise reduction. The aim is to work with a solution which may be used in situations where more sound insulation is required by adding a construction to the existing window, for example during restorations, but could also be affixed during construction of new buildings. The solution allows buildings to retain the existing dimensions of windows allowing for the building design to retain its views, whilst improving the Obtainable sound insulation and retaining the natural ventilation system.
External Protrusions
Protrusions to the facade of a building act as sound barriers to protect the windows behind them. Various forms have been proposed by a number of researchers with each form of the device allowing varying levels of natural ventilation to be achieved during whilst maintaining noise levels. For single directional horizontal protrusions, the acoustical insulation may be calculated using the reduction in the angle of the road to the window/opening. For vertical fins, the protection will be largely limited because of the reflection by this fin, unless appropriate sound absorption is installed. Circumference screen performed better than straight screens whereas eaves/louvres do not provide meaningful acoustical protection.
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