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Sound insulation against external noise is one of the key aspects of minimum sound insulation in building construction. In Germany, it is anchored in DIN 4109 and relates in particular to protection against traffic and industrial noise.
History of the verification method for acoustic insulation against external noise
This article was automatically translated from German into English with the help of DeepL.com
Rules for planning the sound insulation of external building components were published as early as 1973 in a VDI guideline 2719. Subsequently, requirements for the sound insulation of the building envelope were formulated in 1975 via a guideline as a supplementary determination to DIN 4109 and revised again for the 1989 version [1] of this standard. The specification is formulated as a function of a relevant outdoor sound levelLa, which is defined as an A-weighted sound pressure level depending on the outdoor sound situation, e.g. height and types of traffic. In DIN 4109:1989, sound level ranges I to VII were formulated for this purpose, each covering an interval of 5 dB. The weighted sound reduction index R'w was chosen as the requirement parameter for acoustic insulation. To cushion uncertainties, e.g. in the frequency dependence of external noise and sound insulation of the external building components, a flat rate of 5 dB was added to the requirement value.
here using the example of Rosenheim (source: ift Rosenheim)
In the new version of the DIN 4109 series of standards in 2016, the method for acoustic insulation against external noise was largely adopted, only the consideration of night-time external noise levels was newly included in the standardization. An ever-increasing traffic load with higher exterior noise levels led to an increase in complaints and appeals against the standard. Amendments to the ordinances (e.g. elimination of the rail bonus in the Federal Immission Control Act – BImSchG) must also be taken into account. Reinforced construction activity in areas with high noise pollution leads to higher requirement values and therefore more laborious construction measures. This is countered by public pressure to reduce construction costs.
As a first step, the sound level ranges were therefore removed in a revision of DIN 4109-1 in 2018 [2] and a specification in 1 dB increments was introduced. In addition, a special regulation for rail traffic was introduced, which subsequently gave rise to criticism.
Topical studies on acoustic insulation against external noise
In a research project initiated by the DIBt [3], the current situation regarding acoustic insulation against external noise was therefore analyzed. On the basis of these investigations, it was proposed that a more differentiated forecast be carried out for the Evidence of Performance of acoustic insulation so that the flat-rate 5 dB safety margin can be removed.
In order not to introduce any new parameters here, the specifications for sound insulation should be placed as Rw+C and/or Rw+Ctr (i.e. taking into account the spectrum adaptation terms C and Ctr in the frequency range from 100 Hz to 3150 Hz), whereby a differentiation should be made for the type of external noise, see table [1] (only German).
![The table shows a proposal for a new version of the requirements from [3]. Further information on the presentation is available on request at +498031261-2150.](/fileadmin/_processed_/a/d/csm_RFT23_Hessinger_Tabelle_01_Vorschlag_Neufassung_Anforderungen_ba88b7bd52.jpg)
The requirement for the total weighted building sound insulation values R′w,ges + C or R'w,ges + Ctr of the external components of rooms in need of protection depends on the room utilisation and the type of external noise:
Consequences for the sound insulation of external building components
The mathematical Evidence of Performance for this method is based on the existing specifications from DIN 4109-2, however Rw+C and/or Rw+Ctr is now used for the component parameters instead of Rw. Accordingly, in addition to the weighted sound reduction index, the spectrum adaptation terms C and Ctr are also required for external building components. C and Ctr; they have been reported in laboratory tests of building components for over 20 years and must already be verified via the CE declaration for components such as windows, glazing and curtain walls. For other construction elements that were only described in the component catalogue of DIN 4109-35 using an Rw, analyses have been carried out in an ift Rosenheim research project that also make it possible to show spectrum adaptation values for these building components, see Table 2 (only German).
If we look at these numerical values with regard to the new parameters Rw+C and/or Rw+Ctr and consider that the numerical value of the requirement has been reduced by 5 dB in comparisons with the previous standard, we can place a reduction in the requirements for windows in noise situations described with the spectrum adaptation value C and the same average requirements for windows in noise situations described with the spectrum adaptation value Ctr.
Outlook
The DIN 4109 series of standards is currently being revised and will soon be published as a draft. There are currently further discussions on the following points regarding acoustic insulation against external noise:
- Consideration of the maximum level in the determination of the relevant outdoor sound level, this is formulated in DIN 4109-4 as an "optional" regulation
- Consideration of the low-frequency sound insulation of external building components at frequencies below 100 Hz; there are currently no plans to adjust the standard accordingly
Literature
- DIN 4109:1989-11 Acoustic insulation in structural engineering, specifications and Evidence of Performance DIN Media GmbH, Berlin
- DIN 4109-1:2018-01 Acoustic insulation in structural engineering - Part 1: Minimum requirements DIN Media GmbH, Berlin
- Meier, "Noise protection against external noise, specifications for structural acoustic insulation against external noise in accordance with DIN 4109, taking into account the current state of the art as a basis for construction supervision authorities", report No. M143131/02 by Müller BBM
- Saß, Bernd: ift research project 2022 (funded by DIBt) "Ermittlung von Spektrum-Anpassungswerten für Bauelemente zur Integration in DIN 4109-35", topical study on spectrum adaptation terms of construction elements (windows, glass, roller shutter boxes, structural joints), ift research report 2022-11, funded by DIBt
- DIN 4109-35:2016-07 and DIN 4109-35/A1:2019-12 Acoustic insulation in structural engineering, dates for the computational evidence of acoustic insulation (component catalogue) - units, windows, doors, curtain walls DIN Media GmbH, Berlin
Dr. Joachim Hessinger
Dr. Joachim Hessinger studied physics at the University of Mainz and has been working in the area of building acoustics at ift Rosenheim since 1996. Since 2005, he has been Head of Testing Department at the ift Laboratory for Building Acoustics, where tests of windows, facades, glazing, floor elements and timber walls are carried out, and research projects and expert opinions are processed. He shares his experience as a lecturer, speaker and technical author. He is a member of various standards experts and technical committees, for example NA 005-55-74 AA (requirements for acoustic insulation) of the German-Industrial-Norm.