JFDE Journal of Facade Design and Engineering JFDE Journal of Facade Design and Engineering
JFDE / Journal of Façade Design and engineering

063 JOURNAL OF FACADE DESIGN & ENGINEERING VOLUME 5 / NUMBER 1 / 2017

Updated urban facade design
for quieter outdoor spaces

Jochen Krimm1/2, Holger Techen1, Ulrich Knaack2

1 Frankfurt University of Applied Sciences, Department 1/Architecture-Civil Engineering- Geomatics, Nibelungenplatz 1, 60318
Frankfurt , tel. no.+496915333001, Holger.Techen@fb1.fra-uas.de

2 Delft University of Technology, Faculty of Architecture and The Built Environment, Architectural Engineering + Technology,
Julianalaan 132-134, 2628 BL Delft, tel. no.+31 15 27 88566, U.Knaack@tudelft.nl

Abstract

The increasing migration into cities leads to an increasing number of people stressed by noise. More

and more people are moving into urban settings comprised of multiple noise sources and hard reflective

glass and steel facades. The omnidirectional arrangement of noise sources like airborne noise or car

traffic noise and their reflection on the facades neither composes urban arrangements with silent indoor

areas nor comfortable quiet areas outdoor. To come up with requirements for silent areas inside and

outside of buildings further design parameters have to be introduced. The facade is not only a shelter for

the inside it can also provide comfort spaces outside the building. As engineers and architects we cannot

change the noise source, but we can influence the impact on the surrounding urban space by controlling

the reflection of noise emissions on the urban surfaces like facades. In a facade design the capability of

reflecting noise can be tuned by modifying the surface. In order to come up with the acoustical needs

no radical new way of facade design has to be introduced. Mainly a shift of attention to the acoustic

parameters is needed. Based on acoustic measurements of basic geometry principles this research

presents known facade designs and their acoustic parameters regarding the reflection capabilities and

the functions in a facade.

Keywords

acoustics, soundscape, geometry, facades, design parameter, noise,

DOI 10.7480/jfde.2017.1.1422

064 JOURNAL OF FACADE DESIGN & ENGINEERING VOLUME 5 / NUMBER 1 / 2017

1 INTRODUCTION

Reflections on huge facades made out of glass, steel and other hard reflective materials are increasing

the noise levels in public or private spaces of urban agglomerations by redirecting the sound energy to

the urban ground. A field measurement of the authors during the dismantling process of a high-rise

demonstrated that the reflected sound energy can exceed the theoretical level addition of 3 dB(A) up to

8 dB(A) (Techen, & Krimm, 2014). Thus in the vicinity of new or refurbished buildings equipped with

hard reflective facades, the noise levels and the number of noise-affected people will increase. Beside

the measureable and perceivable facade effect the on going migration into major cities is leading to

a growing number of noise-affected people in the official statistics of the EU guided noise mapping

procedure. Based on the noise map regulations defined in the European Noise Directive (END, The

European Parliament and The Council of the European Union, 2002) only cities with more than

100.000 inhabitants have to calculate noise maps. In the framework of the END noise map procedure

the migration into major cities becomes an equivalent of a migration from non-statistically reported

areas to statistically reported ones. In this growing group of the noise-affected people more and more

people are harmed by more than one noise source. This increase is also linked to the migration into

major cities and its growing demand for new households. In order to provide more households office

or industrial buildings were converted into spaces for living. Three exemplarily examples located

in the city of Frankfurt/Main are shown in figure 1 and 2. In these examples at one receiver point

two or more noise sources can be detected. Receiver points in this context are positions in urban

space were people walk or stay. Figure 1 is showing the development area “Lyoner Strasse”. Here

abandoned office buildings are going to be converted into apartment buildings. Due to the business

optimized urban planning from 1962 the former called “Office Town Niederrad” is in short distance to

all important traffic infrastructures like Airport, train station and motorway. The result is a projected

conversion area for 3000 apartments surrounded by up to three or more heavy noise sources: The

aircrafts approaching Frankfurt Airport, the Motorway A5 and the railroad track.

FIG. 1 The situation around the conversion project area of “Lyoner Strasse” in Frankfurt/Main, drawing by the author.

065 JOURNAL OF FACADE DESIGN & ENGINEERING VOLUME 5 / NUMBER 1 / 2017

FIG. 2 New housing areas in Frankfurt/Main close to the railroad and flight tracks, drawing by the author.

Another redensification strategy is the replacement of workshops located in the courtyards by

apartment buildings. Figure 2 shows two conversion areas of former industrial or workshop usage.

The new housing areas in Frankfurt/Main Sachsenhausen are located very close to the main railroad

tracks to Frankfurt main station. The nearby flight track with aircrafts flying in 600 m above ground

is contributing even more high noise levels to the urban acoustic space there. This noise source -

noise receiver setting results in perceivable noise levels outdoors or indoors far above the minimum

comfort levels of 55 dB.

The data of the The Federal Environment Agency of Germany (UBA) are confirming this trend

of migration into noisy areas. In 2014 68 % of the people captured by the noise mapping of

2012 are affected by one or more noise sources (Myck, 2014). More than half of the 68% group of

these inhabitants is affected by two or up to five noise sources. See figure 3.

FIG. 3 People in Germany affected by noise, drawing by the Author, based on Myck, 2014 .

066 JOURNAL OF FACADE DESIGN & ENGINEERING VOLUME 5 / NUMBER 1 / 2017

Furthermore these facts have out-dated the classic architectural tooling like the orientation of

rooms to the silent face of the building. Whenever an urban space is surrounded by noise sources

on street level and in the air, the concept of orientating functions like a sleeping room to the silent

face of a building is not longer possible. Some efforts were made to come up with solutions for

buildings in relation to one noise source. Among others the research conducted by L. Nijs and

F. Kranendonk “Akoestisch optimaleoriëntering van bouwmassa’s nabij verkeerswegen” (Nijs &

Kranendonk, 1979) and “Reclaiming land from urban traffic noise impact zones” from Arc de Ruiter

can be named (de Ruiter, 2005). The research of Martijn Lugten “re-sil(i)ence, design patterns for

an aircraft noise abating spatial environment” from 2014 was focussing on aircraft noise (Lugten,

2014). The ongoing broad research on soundscapes presented in the book Soundscape and the

Built Environment edited by Jian Kang and Brigitte Schulte-Fortkamp is not directly linked to the

architectural solution of a facade design (Kang & Schulte-Fortkamp, 2015). A lot of research was

conducted throughout the years in order to investigate and determine the influence of a facade

on an urban acoustic space. But all these investigations have the limitation that they are dealing

with one specific facade in a specific arrangement. A few examples should explain the problem of

applying these results to the architectural needs of a metropolitan area. In the early investigations

of urban spaces the focus was on the range of acoustic signals in street canyons and on the speech

intelligibility over distance. Among others Wiener Malme and Gogos can be named (Wiener Malme

and Gogos, 1965). Lyon investigated the influence of multiple reflections and their influence on the

sound propagation in an urban space. He recommended the scaled model measuring technique

as a promising tool for a precise sound propagation in three dimensions (Lyon, 1973). Bullen and

Fricke introduced the scattering on facades to their sound propagation model (Bullen&Fricke, 1976).

Picaut and Simon were proofing in 2001 that a given structured facade with its reflection abilities

could be replaced by pure geometry (Picaut&Simon, 2001). Van Renterghem and Botteldooren are

treating the green facade or green roofs in a suburban housing setup with different simulation and

measurement methods (Van Renterghem and Botteldooren, 2008, 2009, 2011). In the research of

Schiff, Hornikx and Forssén, the concept of the noise transmission between shielded canyons was

simulated with numerical and measurement methods (Schiff, Hornikx and Forssén, 2008, 2010).

These research projects were investigating the acoustic and its methods and not the architectural

aspect of it. The scale of the used urban situations is more linked to smaller cities as to major

cities and their high-rises. Furthermore all researched simulation methods except the scaled

model measurement are remaining in two dimensions. From all this research a lot of proposals

for investigating an urban space with several simulation or measurements methods can be drawn

out but only a few recommendations for a facade design can be found. So up to now the impact of

the urbanisation and the influence of the facade on the urban soundscape were neither considered

seriously as architectural design parameters nor translated into an architectural language for

the design of facades.

067 JOURNAL OF FACADE DESIGN & ENGINEERING VOLUME 5 / NUMBER 1 / 2017

2 CASE STUDIES

In the following two case studies the attempt was made to investigate the influence of modified

facade geometries to the noise impact on the surrounding urban space. The scale measurement

method based on the method of dimensional analysis by Lord Rayleigh was used in this geometry

study (Rayleigh, 1915). With this method it became possible to scale measuring setups down to a

smaller size applying the same dimension factor for scaling the setup and the signal to be measured.

The first scale model investigations in engineering were used in the middle of the 18th century for

the analysis of rivers and bridges. Later on the method of scale modelling became common for

the development of aeroplanes, cars, ships, bridges, and concert halls. Scale measurements are

widely used in industry and research because they facilitate testing the impact of changed shapes

or changes in size of downscaled elements, thus saving time and resources. In a 1:1 scaling it is

virtually impossible to change for example the whole construction of a bridge over a valley in order

to select the construction which is delivering a better performance due to airflow in this valley.

The method of scale model engineering used for the acoustical investigations was developed

with recommendations and formulas of D.J. Schuring (Schuring, 1977). When setting acoustical

measurements of an existing urban situation, the building layout has to be scaled by the same factor

as the wavelengths of the audio signal emitted from the source. If the building layout is scaled down

by factor 10 the frequency has to be scaled up by factor 10 to achieve a wavelength scale down of

1:10. Limiting factors to scaling in acoustical measurements are laboratory space and threshold

frequencies of the equipment. In order to focus on pure geometry all scale model surfaces were made

out of hard reflective materials. All scaled measurements done in the framework of this research

were focused on pure geometry because one important limitation of the scaled model measurement

method is difficulty of downscaling material properties. Nevertheless the measurements and their

results stay reliable because whenever a hard reflective geometry is reducing noise levels an

introduction of absorbing material is always improving the acoustical performance. Both cases were

measured in a scaled measurement set-up and in a field measurement. As the case studies should

represent the daily practice in engineering or architectural offices the approach to an acoustic facade

intervention in both case studies was different. In the case study Lyoner Strasse 54 mainly design

decisions led to a facade design. The possible acoustical qualities were considered in a second step.

Opposite to this the facade modifications of the Henninger Turm study were developed for identifying

the acoustical effect of adding horizontal or vertical structures to the south facade.

068 JOURNAL OF FACADE DESIGN & ENGINEERING VOLUME 5 / NUMBER 1 / 2017

2.1 CASE STUDY LYONER STRASSE 54

FIG. 4 The abandoned office building in the Lyoner Strasse 54, picture by the author.

In this study, the urban acoustic space around an eight-storey office building was investigated.

The building is located on the South part of the Lyoner Strasse in Frankfurt/Main, See figure 4.

The 100 m long building is orientated nearly perpendicular to the arrival flight track of Frankfurt

Airport. Refer to figure 5.

In the measurement set-up in the facilities of the German Federal Research Institute for roads and

traffic (BAST) a 1:100 downscaling of the existing situation was built. The model of the building with

the facade modification is shown in figure 6. In this case the facade modification changes the plain

hard reflective surface of the model into a triangulated form of facade geometry. The surface quality

of the facade modification regarding the acoustics remains hard reflective.

The positions of the six measurement points were defined in order to detect the edge effect at the

corners of the building in difference to the measureable effect in middle of the 100 m facade of the

building. With having on both sides three measurement points it will be possible to determine the

emerging effect according to the building face. Refer to figure 7.

069 JOURNAL OF FACADE DESIGN & ENGINEERING VOLUME 5 / NUMBER 1 / 2017

FIG. 5 Drawing of the urban space and its noise sources around Lyoner
Strasse 54, drawing by the author.

FIG. 6 Measurement model in grey colour with
attached facade modification in white, picture by the
author.

FIG. 7 Position of the measurement points around
the building Lyoner Straße 54, drawing by the author.

The moving aircraft in reality was replaced by an air pressure noise source in the scaled

measurement. Because of spatial limitations of the measurement room the original distance of

the airplanes to the building has to be shortened. The air pressure noise source was mounted on a

moving track system in a height of 150 cm above ground and in a distance of 261 cm to the building

in order to meet the geometrical conditions of the existing situation. With this equipment it was

possible to measure appearing noise levels at the predefined points around the building. The moving

track of the noise source in conjunction with the measurement system delivered a set of frequency-

distributed levels in the range between 100 Hz and 2000 Hz at every 1 cm. The single dB values

for every point on the moving track were then calculated out of the frequency-distributed levels.

The measurements were proceeded with the facade modification and repeated without. Subtracting

the measured levels without facade modification from the captured data with the facade modification

delivers the resulting level change. The result for the facade modification at measurement point

West2 and OST2 is shown exemplarily in the graphs in figure 8.

070 JOURNAL OF FACADE DESIGN & ENGINEERING VOLUME 5 / NUMBER 1 / 2017

FIG. 8 Measurement results for Lyoner Strasse 54 linked to the airplane position, measurements of the author at the facilities of
the BAST.

The graph in figure 8 is impressively depicting that around a solitaire building an effect of a facade

modification is delivering level changes more than the theoretical 3 dB. For the point t2 the level

change at the measuring position OST2 is -7 dB. The measurement data give evidence for the

possibility of reducing noise levels during an aircraft noise event around a freestanding building.

2.2 CASE STUDY HENNINGER TURM

The urban plot around the Henninger Turm in Frankfurt/Main was taken as a basic layout for an

investigation of facade modifications and their impact on the urban acoustics in the vicinity of a

building. Measurement and noise source positions are defined by the field measurement positions

from 2013 (Techen, & Krimm, 2014). As there was no moving noise source in the measurement

facilities available for the simulation of a flying airplane, the measurements were done using a

ring radiator as a point source in two positions. The two positions of the point noise source were

representing two points in time of the moving airplane on the flight track. The noise source position

“on axis” was perpendicular to the south facade of the tower. The “off axis” noise source position was

angled 19 degree away from the normal of the south facade. For an overview of the measurement

points and the layout of the set-up refer to figure 9.

071 JOURNAL OF FACADE DESIGN & ENGINEERING VOLUME 5 / NUMBER 1 / 2017

H enninger
Turm

O ffic e
B uilding

P O 1
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pos ition

PO2

PO1

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Pos 2

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Pos 4

Microphone positions

Mea s urement “ O n-a x is “ Mea s urement “ O ff-a x is “
FIG. 9 Measurement positions (measurement points) in the scaled measurement setup, drawing by the author.

FIG. 10 Measurement set-up in a 1:50 down scaling at the measurement facilities at TU Delft, picture by the author.

The measurements were taken in the facilities of the Laboratory of Acoustical Wavefield

Imaging, Department of Imaging Physics at the Delft University of Technology by the author.

The measurement model in the scale of 1:50 consists out of planed beech wood blocks representing

the building on-site of the field measurement around the Henninger Turm. In figure 10 the set-up in

the anechoic chamber at TU Delft is shown.

On the plain facade of the tower model smaller beech wood blocks could be added in different

configurations. For this row of measurement sequences the facade modifications were classified

in horizontal oriented modifications and vertical oriented modifications. In these two classes, the

implemented variation of density in the arrangement of blocks results in varying sizes of the front

face area. Additional to that, blocks with one tilted face were used in the class of the horizontal

arrangement gaining for an insight on the effect of downward or upward reflection. The Sizes of the

beech wood blocks were representing facade modifications in the dimension of 0.5 m x 1.5 m x 3.0 m

or 1.0 m x 1.5 m x 3.0 m. Figure 11 shows the measured facade variations and their abbreviations.

072 JOURNAL OF FACADE DESIGN & ENGINEERING VOLUME 5 / NUMBER 1 / 2017

FIG. 11 List of the measured surface modifications, drawing by the author.

Aiming for a more detailed view on the frequency distributed noise levels and the noise coverage of

the urban space four measurement points in front of the facade modification were introduced in this

setup. With these four points the measurement data was evaluated due to the frequency-distributed

level in each measuring point. As the frequency-distributed levels are not so clear readable in

terms of the acoustical impact of a facade modification the method of calculating single values out

of frequency-distributed levels was used. The average frequency distributed noise level of each

of the four measuring points was calculated out of the frequency distributed noise level values of

the single measurement points. In order to obtain insight on the effect of a facade modification the

change of noise levels was calculated by subtracting the measured level values of the modification

from the level values of the reference model ref01 measured in the sequence. The change of noise

levels in relation to the reference model was calculated for average noise level for the validated

frequency range of 25 Hz to 630 Hz in one microphone position and in all four microphone positions.

The results for the measurement sequence of the facade modifications “ref02 v1 - v3” are shown

exemplarily in the following. The graphs are showing results from two defined arrangements of

noise source and measurement position. If the noise source is on axis with the active measurement

point the measurement is defined as a “on axis” measurement. Whenever the measurement position

is not in the axis of the noise source to the measured object, the measurement is defined as “off

axis”. Calculating the average out of the frequency distributed level data set for each measuring

point delivers a single value on the broadband weighting of one surface modification regarding one

measuring point. The results are showing for the “on axis” measurement a level reduction from 0,25

dB up to 0,5 dB. The values from the “off axis” measurement are detecting a maximum level change

to the reference model from 0,15 dB, refer to figure 12.

073 JOURNAL OF FACADE DESIGN & ENGINEERING VOLUME 5 / NUMBER 1 / 2017

FIG. 12 Level changes for the facade modifications ref02 v1, refo2 v2 and ref02 v3. Measurements on-axis and off-axis conducted
by the author.

The measurement with the noise source positioned on axis indicates level changes for the averaged

noise level of the validated frequency range up to -0,6 dB. The values derived from the measurement

with the noise source located off axis results in an average noise level change in the range of -0.1

dB for the three surface modifications. Data of all four positions were used to obtain information on

the noise coverage of the area in front of the south facade. Therefore the four averaged frequency-

distributed levels of each microphone position were averaged resulting in one level value for

each surface modification within the validated level range of 25 Hz to 630 Hz. The result draws an

oppositional picture to the averaged value for one microphone position. Each surface modification is

increasing the level when taking all four points into account, refer to figure 13.

The data of this geometry design study represented in the graphs is indicating that the effects of

surface modifications on a facade are located in spots. At the locations of the spots a level change of

3 dB can be measured. Putting this into the perspective of inspecting all four measurement points

simultaneously the effect switches from a level increase of 0,6 dB to a level decrease of 0,2 dB.

Remarkable is here not the small level change below 1 dB but the switching from a level decrease to

an increase when the whole area of the four measurement points was taken into account. Only with

an evaluation of all measurement data in a table a “best modification” can be detected. See table 1.

074 JOURNAL OF FACADE DESIGN & ENGINEERING VOLUME 5 / NUMBER 1 / 2017

FIG. 13 Averaged noise level values for positions 1-4, measured on-axis and off-axis.

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dB Hz Sp1/MP 1 Sp1/MP 2 SP 1/MP1 SP2/MP2

Ref02 V1 hor. 1 -1.9 dB 160 hz -0.3 dB 0.0 dB +0.2 dB +0.1 dB

Ref02 V2 hor. 2 -2.6 db 400 Hz -0.4 db 0.0 dB +0.2 dB 0.0 dB

Ref02 V3 hor. 3 - 3.0 dB 400 Hz -0.6 dB -0.1 dB +0.4 dB + 0.1 dB

Ref03 V1 hor. 1 -1.9 dB 200 Hz -0.4 dB 0.0 dB +0.3 dB +0.1 dB

Ref03 V1u hor. 1 -3.2 dB 250 Hz -0.2 dB 0.0 dB +0.3 dB +0.1 dB

Ref03 V2 hor. 2 -3.5 dB 250 Hz -0.4 dB 0.0 dB +0.3 dB +0.1 dB

Ref03 V2u hor. 2 -4.5 dB 250 Hz -0.9 dB 0.0 dB +0.5 dB +0.1 dB

Ref03 V3 hor. 3 -3.2 dB 250 Hz -0.4 dB 0.0 dB +0.4 dB +0.1 dB

Ref03 V3u hor. 3 -4.9 dB 250 Hz -0.9 dB 0.0 dB +0.5 dB +0.1 dB

Ref04 V1 vert. 1 -1.9 dB 200 Hz -0.2 dB +0.6 dB -0.2 dB -0.3 dB

Ref04 V2 vert. 2 -2.4 dB 160 Hz -0.2 dB +0.5 dB -0.2 dB n.a.

Ref04 V3 vert. 3 -2.7 dB 160 Hz -0.4 dB +0.5 dB -0.2 dB -0.4 dB

Ref04 V4 vert. 4 -4.4 dB 400 Hz -0.5 dB +0.5 dB 0.0 dB -0.3 dB

Ref04 V5 vert. 5 -3.5 dB 400 Hz -0.4 dB +0.5 dB -0.1 dB -0.4 dB

Ref05 V1 hor. 1 -1.8 dB 400 Hz -0.2 dB 0.0 dB +0.1 dB 0.0 dB

Ref05 V2 hor. 2 -3.3 dB 400 Hz -0.6 dB 0.0 dB +0.2 dB 0.1 dB

TABLE 1 The calculated results of the measured sequences

075 JOURNAL OF FACADE DESIGN & ENGINEERING VOLUME 5 / NUMBER 1 / 2017

3 CONCLUSION

Both case studies are pointing out that acoustical design of facades has to be individually measured

and evaluated. The use of the scale measurement method gives the possibility to engineers and

architects to introduce geometric surface modifications to a building design process whenever

an acoustical approach is needed. The measurements can be introduced according to the design

stage of a project. With the scaled measurement method it is possible to investigate geometric

details of an acoustic design in a 1:10 downscaling as it is possible test a building geometry with

1:100 models. The effects on the urban space in relation to the facade can be predicted and tuned

to a complete coverage without an overall decreased noise level. If we want to come up with the

challenge of creating a lively and comfort environment in the process of an increasing urbanisation

the tool of scaled measuring has to be introduced to architectural design processes in order to define

the geometrical basis for acoustically comfortable spaces. The even more remarkable outcome

of the case studies is that all observed level changes were caused only by a change of geometry.

No material properties were yet involved in the studies. All achieved level changes in both case

studies could be optimised in further developments. The results of acoustical effective facades could

be tuned by introducing specially shaped perforations of the facade surface or by adding materials

with acoustical properties to the building envelope.

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