The effect of sound absorbing surfaces for acoustic planning of road infrastructure
Doctoral thesis, 2026
Traffic noise has a negative impact on concentration and learning, causes annoyance, sleep disturbance, impedes recuperation and relaxation and increases the risk of cardio-vascular disease, mental illness and premature deaths. Traffic noise is a particular urban problem; more than 20 % of the population in the EU is exposed to traffic noise levels which are harmful to health, with road traffic being the dominating source.
This thesis is focused on road traffic noise from large-scale infrastructure situated in urban areas. These environments, with multi-lane roads, bridges, ramps, supporting walls and noise barriers as well as adjacent building façades, form complex landscapes of thousands of square meters of sound reflecting surfaces.
In this PhD project it has been investigated whether it is necessary to adjust or complement the Nord2000 road noise prediction method to assess the noise levels in urban areas more accurately. Suggestions have been made for improving noise calculations and predictions of the noise-reducing effect of changes in the absorption indices of surfaces in infrastructure.
Absorption data to use in the calculations were obtained with the SOPRA method for measuring the sound reflection index of road noise barriers in-situ, i.e., in direct sound field. The data were subsequently used in the Nord2000 model to calculate the effect of applying absorbers on existing noise barriers at real sites. Both the placement and the type of absorber were investigated. The studies showed that: (1) Absorbers reduce the traffic noise levels. (2) The effect of absorbers is strongly site dependent. (3) Different types of absorbers result in different noise level reductions.
Furthermore, an evaluation of the Nord2000 results using the Boundary Element Method (BEM), indicates that Nord2000 may underestimate the effect of absorbers on noise barriers, especially for situations involving multiple reflections between the noise barrier and other vertical surfaces.
With the results of this project, the intention is to continue the work towards a methodology for acoustic planning of road infrastructure.
This thesis is focused on road traffic noise from large-scale infrastructure situated in urban areas. These environments, with multi-lane roads, bridges, ramps, supporting walls and noise barriers as well as adjacent building façades, form complex landscapes of thousands of square meters of sound reflecting surfaces.
In this PhD project it has been investigated whether it is necessary to adjust or complement the Nord2000 road noise prediction method to assess the noise levels in urban areas more accurately. Suggestions have been made for improving noise calculations and predictions of the noise-reducing effect of changes in the absorption indices of surfaces in infrastructure.
Absorption data to use in the calculations were obtained with the SOPRA method for measuring the sound reflection index of road noise barriers in-situ, i.e., in direct sound field. The data were subsequently used in the Nord2000 model to calculate the effect of applying absorbers on existing noise barriers at real sites. Both the placement and the type of absorber were investigated. The studies showed that: (1) Absorbers reduce the traffic noise levels. (2) The effect of absorbers is strongly site dependent. (3) Different types of absorbers result in different noise level reductions.
Furthermore, an evaluation of the Nord2000 results using the Boundary Element Method (BEM), indicates that Nord2000 may underestimate the effect of absorbers on noise barriers, especially for situations involving multiple reflections between the noise barrier and other vertical surfaces.
With the results of this project, the intention is to continue the work towards a methodology for acoustic planning of road infrastructure.
urban infrastructure
sound absorption
Nord2000
Direct Field Absorption model.
RIQ
direct sound field
Road traffic noise
sound reflection index
SOPRA in-situ measurement method
noise barriers
SB-L285
Opponent: Prof. Dr. ir. Timothy Van Renterghem Full Professor, Ghent University, Department of Information Technology Institute of Biomedical Engineering (iBME/Noise & Health), Gent, Belgium
Author
Monica Waaranperä
Chalmers, Architecture and Civil Engineering, Applied Acoustics
Modelling of spherical wave reflection on an absorbing flat surface considering its finite size – Application to traffic noise barriers
Applied Acoustics,;Vol. 243(2026)
Journal article
Time-domain model for spherical wave reflection in a flat surface with absorber character – Application to the SOPRA measurement method
Applied Acoustics,;Vol. 227(2025)
Journal article
MEASUREMENT OF SOUND REFLECTION USING THE SOPRA METHOD
Proceedings of Forum Acusticum,;(2023)
Paper in proceeding
Why noise control must be considered in the context of sustainable development
Internoise 2022 - 51st International Congress and Exposition on Noise Control Engineering,;(2022)
Paper in proceeding
Application of absorption data from SOPRA sound reflection index measurements in Nord2000 road noise calculations – results from a case study
Application of absorption data from SOPRA sound reflection index measurements in Nord2000 road noise calculations – results from a case study,;(2026)
Paper in proceeding
Environmental noise is a major public health concern in Europe, primarily driven by road traffic.
Traffic noise causes annoyance, sleep disturbance, increases the risk of cardiovascular disease, diabetes, mental illness and premature death. Moreover, the environmental noise affects concentration and learning negatively and children are especially vulnerable. It is a particular urban problem, growing with urbanization - a trend all over the world. Within EU countries only, more than 110 million people are exposed to traffic noise levels which are harmful to health, for which road traffic is the primary cause.
This thesis focuses on large-scale urban road infrastructure, i.e., the largest roads in our cities with many lanes, bridges, walls and sometimes noise barriers, surrounded by buildings. The noise from the traffic is reflected on all hard surfaces, which increases the noise level in the surroundings. In this project, it has been investigated if sound absorbing surfaces instead of reflecting surfaces would reduce the traffic noise levels in urban environments. This was done by calculations, simulating changes of the acoustic properties of noise barriers in real sites. The absorption data for the calculations was obtained by in-situ measurements of sound absorbing noise barriers and other walls in infrastructure.
The studies showed that: (1) Absorbers can reduce traffic noise levels. (2) The effect of absorbers depends on the site; what may be a good solution for one place may not be the best in another, even along the same road. (3) Different types of absorbers result in different noise level reduction.
Actions for improving noise calculations are also suggested in order to assess the noise situation in urban environments more accurately and to be able to prove the effect of installing absorbers or changing the acoustic characteristics of the surfaces in the infrastructure.
Traffic noise causes annoyance, sleep disturbance, increases the risk of cardiovascular disease, diabetes, mental illness and premature death. Moreover, the environmental noise affects concentration and learning negatively and children are especially vulnerable. It is a particular urban problem, growing with urbanization - a trend all over the world. Within EU countries only, more than 110 million people are exposed to traffic noise levels which are harmful to health, for which road traffic is the primary cause.
This thesis focuses on large-scale urban road infrastructure, i.e., the largest roads in our cities with many lanes, bridges, walls and sometimes noise barriers, surrounded by buildings. The noise from the traffic is reflected on all hard surfaces, which increases the noise level in the surroundings. In this project, it has been investigated if sound absorbing surfaces instead of reflecting surfaces would reduce the traffic noise levels in urban environments. This was done by calculations, simulating changes of the acoustic properties of noise barriers in real sites. The absorption data for the calculations was obtained by in-situ measurements of sound absorbing noise barriers and other walls in infrastructure.
The studies showed that: (1) Absorbers can reduce traffic noise levels. (2) The effect of absorbers depends on the site; what may be a good solution for one place may not be the best in another, even along the same road. (3) Different types of absorbers result in different noise level reduction.
Actions for improving noise calculations are also suggested in order to assess the noise situation in urban environments more accurately and to be able to prove the effect of installing absorbers or changing the acoustic characteristics of the surfaces in the infrastructure.
Driving Forces
Sustainable development
Areas of Advance
Transport
Health Engineering
Subject Categories (SSIF 2025)
Other Civil Engineering
Infrastructure Engineering
DOI
10.63959/chalmers.dt/5937
ISBN
978-91-8103-480-6
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5937
Publisher
Chalmers
SB-L285
Opponent: Prof. Dr. ir. Timothy Van Renterghem Full Professor, Ghent University, Department of Information Technology Institute of Biomedical Engineering (iBME/Noise & Health), Gent, Belgium