Temporary improvement of the airborne sound insulation of windows with external closures to maintain airborne sound insulation at night

In DIN 4109-2:2018-01, an increased nocturnal disturbance effect due to external noise is taken into account by adding 10 dB to the rating level during this period. The relevant external noise level is then calculated from the period with the higher resulting rating level. Practice shows that the night period can be decisive for the design of sound insulation in many noise situations, e.g. railroad lines with night-time freight traffic. In order to avoid a further increase in construction costs due to oversizing, the research project is investigating the extent to which external closures can contribute to compliance with airborne sound insulation at night and how these can be taken into account in the forecast in a simple way. In addition to analyzing measurements from existing databases, further component measurements with different external closures will be taken. A semi-empirical prediction model and a finite element model are developed for a prediction and validated with the measurements. The results will be made available to the standardization committees.

Project background

The building law requirements for the airborne sound insulation of external building components are defined in DIN 4109-1:2018-01. The requirement is based on the degree of protection required and the external noise level. In the current version of DIN 4109-2:2018-01, an explicit consideration of the external noise level at night has been introduced. If the external noise level at night is not more than 10 dB lower than during the day, the sound insulation is designed using the relevant external noise level at night plus a supplement of 10 dB to take into account the increased nocturnal disturbance effect (greater need for protection at night). It has been shown that there are now many noise situations, particularly on railroad lines with night-time freight traffic, where this is not the case. When implementing the required sound insulation, this sometimes leads to significantly increased sound insulation values for windows, which then lead to expensive multi-layered constructions such as composite or box-type windows.

A simple solution to the problem would be temporary sound insulation in the form of external shutters, such as roller shutters or window shutters, which can be switched on during the noisy night-time hours. The "day/night division" with regard to the determination of sound insulation requirements also opens up the fundamental approach of differentiating between day and night with regard to the building acoustic requirements for external components. However, the consideration of such temporary sound insulation is currently not regulated in DIN 4109 and is therefore not permitted.

Even if the planned project is primarily motivated by the national building law requirements in accordance with DIN 4109, the findings can and should be passed on to other regulators and taken into account in the relevant regulations.

Project objective

The main objectives of the project can be defined as follows:

Development of a verification procedure for the consideration of temporary sound insulation in DIN 4109-2
Development of a component catalog to verify the improvement of the airborne sound insulation of a window by using an external closure. The component catalog takes into account the essential design parameters.
Development of a draft standard agreed with the standardization committee NA005-55-75 AA to supplement DIN 4109-35

Project procedure

The project objectives are to be achieved essentially through experimental and numerical investigations of the airborne sound insulation of windows in conjunction with external closures. The measurements are carried out in accordance with DIN EN ISO 10140-1:2021-09 at ift Rosenheim. In order to gain a deeper understanding of the improvement in the airborne sound reduction index, the vibroacoustic coupling of the window with the external closure is to be investigated by means of appropriate measurement instrumentation of the cavity with microphones and structure-borne sound transducers. These measurements then serve as validation for finite element models, which model the excitation of the components and the coupling of the space between the panes by including the fluid-structure coupling. The modeling is the task of Rosenheim University of Applied Sciences.

A component catalog can be defined and proposed by varying the parameters that are significant for improving airborne sound insulation.

Experimental tests in accordance with DIN EN 1026:2016-09 are carried out at ift Rosenheim to assess the airtightness of the measured closures.

Before the experimental tests on airborne sound insulation, a statistical analysis of the ift measurement database is carried out, which also contains measurements of the airborne sound insulation of windows with external closures. However, it is to be expected that the existing measurements only contain constructions with a rather small distance between the closure and the window.

The Stuttgart University of Applied Sciences is further developing a semi-empirical calculation model based on the frequency-dependent sound insulation values of windows with different closures. This should make it possible to determine the single value of the resulting weighted sound insulation of the overall construction. The aim is to develop the key results as a standardization proposal for DIN 4109-2 and Part 35.

Innovation

Closures such as roller shutters, folding shutters and sliding shutters can be used to improve the airborne sound insulation of the window when it is closed. Increased airborne sound insulation could therefore be implemented for special noise pollution at night. This would make it possible to dispense with highly sound-insulating and cost-intensive window constructions. In this way, the current political goal of avoiding an increase in construction costs can be taken into account.

However, the consideration of such temporary sound insulation is not yet regulated or permitted in DIN 4109. Furthermore, there is a lack of generally valid data for both planners and contractors as to which improvements in airborne sound insulation can be achieved in conjunction with which design variants of external closures. The development of a component catalog thus provides planners and contractors with the necessary information.

The possible integration of the developed component catalog into EN 14351-1 also makes CE marking possible for such products without additional testing.