Thin low frequency sound absorbers using rigid mineral foams
Porous materials are surely the most widely used solutions when it comes to acoustic treatments. They provide good absorption features for a large range of frequencies while being extremely cheap to manufacture. However, controlling their internal structure and macroscopic properties are far from trivial, and they display poor absorption capabilities in the sub-wavelength domain. The latter is often dealt with resonant and/or periodic structures, often called metamaterials, which can provide extra-ordinary absorption performances.
As noise mitigation becomes a predominant matter in modern society, the design of cheap, efficient at low frequencies, and resilient acoustic treatments is of great interest. Preliminary studies on mineral foams have addressed the acoustic behaviour of such materials, and are readily available in the scientific literature. Tests under lab conditions show that the unique foams with large pores and thin pore walls absorb low frequencies better than existing products, but only in a narrow band. A model will enable the design of a high-performance sound absorption material, for which a suitable production process will be developed. In addition mineral foams are fire resistant and do not emit plasticizers thus are safe for in- and outdoor use.
Contact: Bart Van Damme
Funding: Innosuisse
Partner: de Cavis
Duration: 2021 - 2023

DD-FORMS: Data-driven fast optimization of resonant metamaterial structures
In recent years, resonant metamaterials have garnered much interest because of their potential to break with traditional design principles in noise and vibration management. By virtue of a carefully designed micro- or mesostructure, metamaterials display exotic macroscopic properties, such as vibrational band gaps, that do not exist in known bulk materials. However, modeling and optimizing these emergent properties is a challenging multiscale problem. The process remains computationally intractable in many cases due to the heavy reliance on expensive finite-element analyses and/or topology optimizations.
To address this challenge, the present project focuses on applying data science techniques in the design of resonant metamaterial structures. In particular, we target vibration reduction in finite-sized elastic plates by integrating 3D-printed mechanical resonators, which is treated as an optimization problem in both the arrangement and the dynamics of the resonators. Where possible, costly high-fidelity simulations and optimizations will be replaced with data-driven surrogates to drastically reduce the computational load. On the one hand, the inverse design problem of creating resonators with a desired dynamic response will be addressed, for instance by applying tandem neural networks. On the other hand, we will investigate the optimal arrangement of resonators for maximum vibration reduction. Here, Bayesian optimization techniques may offer an efficient solution. The range of material and geometric properties obtainable via the 3D-printing process will be identified and taken into account.
Contact: Bart Van Damme
Funding: SDSC
Partner: SDSC, Laboratory for Advanced Materials Processing (Empa)
Duration: 2021 - 2023

Toward prevention of health effects from acute and chronic noise exposure
In recent years, epidemiological research has shown links between various cardiometabolic diseases and road traffic, railway and aircraft noise. However, little is known about the effects on mental health and the most effective interventions to reduce noise-related health effects. This study examines several important research questions related to short- and long-term health effects of traffic noise.
To investigate the acute effects of aircraft noise on the mental health of patients in a psychiatric hospital, a time series analysis is used to compare daily measured and modelled aircraft noise exposure from a nearby airfield with aggression events, daily medication use and patients' mental health. In another sample of 650 persons aged 20 to >80 years, we investigate whether and to what extent physical activity and sleep influence the effect of road traffic noise on early detectable markers of cardiometabolic disease. In the last 20 years, an estimated 350'000 and 400'000 persons in Switzerland benefited from noise barriers and soundproof windows, respectively. The effect of these measures on cardiovascular mortality is retrospectively investigated in the Swiss National Cohort using a natural experimental approach. For this purpose, spectral propagation algorithms are implemented in current noise models. The analysis will also consider changes in noise exposure due to low-noise pavements, large infrastructures and relocations.
The study will improve our understanding of effective prevention measures at the individual and population level. For individual prevention, comprehensive analyses of physiological effects on the cardiovascular system and metabolism will shed light on whether and to what extent noise effects are preventable at an early stage. With regard to structural prevention, it is now empirically investigated for the first time how noise protection measures affect cardiovascular mortality. In addition, the project provides insights into the effect of noise in a possibly particularly sensitive population group of psychiatric patients.
Contact: Beat Schäffer
Funding: SNF
Partner: Swiss TPH, n-Sphere
Duration: 2021 - 2024

Soil Vibration and Auralisation Software Tools for Application in Railways (SILVARSTAR)
The overall goal of SILVARSTAR is to provide the railway community with proven software tools and methodologies to assess the noise and vibration environmental impact of railway traffic on a system level. The first overall objective of SILVARSTAR is to provide the railway community with a commonly accepted, practical and validated methodology and a userfriendly prediction tool for ground vibration impact studies. This tool will be used for environmental impact assessment of new or upgraded railways on a system level. It will provide access to ground vibration predictions to a wider range of suitably qualified engineers and will facilitate project planning and implementation by improved simulation processes.
The second overall objective of SILVARSTAR is to develop a fully functional system for auralisation and visualisation based on physically correct synthesised railway noise, providing interfaces with Virtual Reality visualisation software. This system will facilitate communication with the public, decision makers and designers through virtual experience before delivery of projects.
Empa is responsible for the second overall objective of SILVARSTAR and leads the corresponding work package and conducts the major work on the development of a fully functional system for auralisation of railway noise.
Contact: Reto Pieren
Funding: Horizon 2020, Shift2rail
Partner: Empa, University of Southampton, KU Leuven, VibraTec, Wölfel, unife, Bandara VR
Duration: 2020 - 2022

Restorative potential of green spaces in noise-polluted environments (RESTORE)
Urban areas experience a continuous increase of population and mobility going along with increased noise exposure of the residents and a decline of green spaces. The objective of this project is to assess the effects of green spaces as facilitators and noise as impediment to recover from stress. The project consists of laboratory experiments with VR and soundscape simulations, field experiments in urban and suburban green spaces of varying acoustic and visual settings, an extended field study in differently noise-polluted neighbourhoods, and a Swiss-wide survey and remote sensing assessment of green spaces. The project will provide new insights in the pathways of stress build-up as evoked by noise exposure, and recovery as promoted by green spaces. It will identify the visual and acoustic prerequisites of restorative green spaces, and have an impact on the Swiss noise legislation and the implementation of the revised spatial planning act.
Contact: Jean Marc Wunderli, Beat Schäffer
Funding: SNF (Sinergia)
Partner: WSL
Duration: 2020 - 2024

BOHEME’s ambitious goal is to design and realize a new class of bioinspired mechanical metamaterials for novel applicative tools in diverse technological fields. Metamaterials exhibit exotic vibrational properties currently unavailable in Nature, and numerous important applications are emerging. However, universally valid design criteria are currently lacking, and their effectiveness is presently restricted to limited frequency ranges. BOHEME starts from an innovative assumption, increasingly supported by experimental evidence, that the working principle behind metamaterials is already exploited in Nature, and that through evolution, this has given rise to optimized designs for impact damping. The “fundamental science” part of the project aims to explore biological structural materials for evidence of this, to investigate novel optimized bioinspired designs (e.g. porous hierarchical structures spanning various length scales) using state-of-the-art analytical and numerical approaches, to design and manufacture vibrationally effective structures, and to experimentally verify their performance over wide frequency ranges. The project involves theoretical, numerical and experimental aspects, and is a high-impact endeavour, from which basic science, EU industry and society can benefit.
Contact: Andrea Bergamini
Funding: Horizon 2020
Partner: UNITN, Imperial, IMP-PAN, ETH Zürich, UNITO, Multiwave, Phononic Vibes, POLITO, CNRS
Duration: 2020 - 2023

Optimized high-lift system for low noise approaches, including best configuration for landing (DYNCAT)
DYNCAT aims at enabling more environmentally friendly and more predictable flight profiles in the Terminal Manoeuvring Area TMA, namely on approach, by supporting the pilots in configuration management. Approach and take-off operations at busy airports are virtually always less noise and fuel efficient than possible due very rigid constraints imposed on the flight profiles by Air Traffic Control ATC (concerning both vertical profiles and speed regimes), but also due to lack of support to the pilots for dealing with given restrictions/constraints and actual weather in the optimum way. Current FMS functionalities do not support configuration management very well, only a simplified, static high-lift sequence with a fixed order is available. The adequacy of actual procedure flown depends very much on the pilots' skills, but also on their access to information such as actual wind situation and ATC intents.
The objectives of the project are (a) to analyze the impact of current mismatch of aircraft and ATC procedures on flyability (pilot workload, safety) and environmental impact (fuel burn and CO2; noise), (b) to propose amendments to on-board and ground procedures including identification of necessary enablers (technical, regulatory) and (c) to quantify ecological and economical potential of proposed improvements, including the prediction of 4D Trajectories, through exemplary analysis and early prototype simulation of newly designed configuration management functionality.
The study will be done exemplarily using the A320 family as reference aircraft and the development of new FMS functionalities for the optimization of the high-lift system sequencing during approach as use case. Access to recordings of actual flight operational data, associated ATC instructions issued, weather data and noise measurements for a large number of operations in Swiss airspace on one hand and the implementation of the improved functionalities on an industrial test platform on the other allow for high validity and relevance of the results.
Contact: Jean Marc Wunderli
Funding: Horizon 2020 (SESAR)
Partner: DLR, Swiss Airlines, THALES, SkyLab
Duration: 2020 - 2022

Multisensory dimensions of forest attractiveness
Current research results provide clear indications that negative effects of noise, both in terms of annoyance and health effects, can be reduced by the presence of green spaces and recreational areas. Particularly in urban areas, the design of public spaces and the maintenance and promotion of local recreational areas can therefore contribute to reducing the negative effects of noise pollution. These forms of noise protection shall be evaluated with regard to their effectiveness and further developed in their implementation in order to meet the conflicting requirements of noise protection and spatial planning. Within the framework of this project, Empa, in collaboration with WSL, will investigate the question of what requirements forests in urban areas must meet in order to fulfil their function as recreational areas, and what defines the quality of forest recreation areas.
Contact: Jean Marc Wunderli
Funding: FOEN
Partner: WSL
Duration: 2020

Impact sound insulation of solid wood floors with acoustic black hole (TriMASL)
Use of so-called "acoustic black holes" to improve the impact sound insulation in solid wood floors. This reduces the mass of floor toppings that was previously necessary for sound-insulation, thus further expanding the technical and economic advantages of timber construction. The aim of the investigation is the development of design and optimization methods and the implementation of a technology de-monstrator.
Contact: Stefan Schoenwald
Project funding: BAFU
Duration: 2019 - 2021

Localization and Identification Of moving Noise sources (LION)
Sound source localisation methods are widely used in the automotive, railway, and aircraft industries. Many different methods are available for the analysis of sound sources at rest. However, methods for the analysis of moving sound sources still suffer from the complexities introduced by the Doppler frequency shift, the relatively short measuring times, and propagation effects in the atmosphere. The project LION combines the expertise of four research groups from three countries working in the field of sound source localisation: The Beuth Hochschule für Technik Berlin (Beuth), the Turbomachineryand Thermoacoustics chair at TU-Berlin (TUB), the Acoustic Research Institute (ARI) of the Austrian Academy of Sciences in Vienna and the Swiss laboratory for Acoustics / Noise Control of EMPA. The mentioned institutions cooperate to improve and extend the existing methods for the analysis of moving sound sources. They want to increase the dynamic range, the spatial, and the frequency resolution of the methods and apply them to complex problems like the analysis of tonal sources with strong directivities or coherent and spatially distributed sound sources. The partners want to jointly develop and validate these methods, exploiting the synergy effects that arise from such a partnership. Beuth plans to extend the equivalent source method in frequency domain to moving sources located in a halfspace, taking into account the influence of the ground and sound propagation through an inhomogeneous atmosphere. ARI contributes acoustic holography, principal component analysis, and independent component analysis methods and wants to use its experience with pass-by measurements for trains to improve numerical boundary element methods including the transformation from fixed to moving coordinates. TUB develops optimization methods and model based approaches for moving sound sources and will contribute its data base of fly-over measurements with large microphone arrays as test cases. EMPA contributes a sound propagation model based on TimeVariant Digital Filters with particular consideration of turbulence and ground effects and will also generate synthetic test cases for the validation of sound source localization algorithms. The project is planned for a period of three years. The work program is organized in four work packages: 1) the development of algorithms and methods, 2) the development of a virtual test environment for the methods, 3) the simulation of virtual test cases, and 4) the application of the new methods to existing test cases of microphone array measurements of trains and aircraft.
Contact: Jean Marc Wunderli
Funding: SNF (Lead Agency Project)
Duration: 2020 - 2023

Man - made elastic structures (often referred to as metastructures) are promising in applications where filtering, focusing or channeling of elastic waves is required. Few examples encompassing different length scales include shielding of buildings from seismic waves, enhanced damping of undesired vibrations of industrial machinery, frequency up-conversion or down-conversion.  However, as we head towards metastructure's massproduction, some important limitations associated with their modelling need to be addressed.  In fact, current models of their dynamic response mainly rely on structural periodicity and bulk behavior. The first and main goal of this project is to develop efficient and accurate FEM algorithms able to predict the dynamic response of non-periodic metastructures, embedded into hosting elastic materials.  The second objective of the project is to validate those simulation tools on the dynamic response of aperiodic metastructures, whose tiling involves two or more overlapping periodicities. We envisage the use of (I) model-order-reduction techniques - to mitigate the numerical demand of the proposed metastructures (complex geometries, irregular boundaries) - and (II) topological optimization techniques - to achieve desired dynamic properties. The proposed materials-by-designs will finally be tested experimentally using 3D-printed prototypes.
Contact: Bart Van Damme
Funding:  Empa
Duration: 2019 – 2021

Data Science Enabled Acoustic Design – AADS
Ansprechpartner: Kurt Heutschi
Projekförderung: Swiss Data Science Center
Projektpartner: Swiss Data Science Center, Gramazio Kohler Research - ETH Zürich, Strauss Electroakoustik
Dauer: 2018-2020

OSCAr: Acoustically optimized street canyons
Street canyons in urban areas with a high building density exhibit challenging acoustic environments for the residents and passerby. The multiple sound reflections between the opposite facades not only enhance the noise level and consequently noise annoyance, but can also impair speech intelligibility and acoustic comfort.  
Mandated by the Federal Office for the Environment FOEN, Empa is investigating the acoustic quality in street canyons. Thereby, various building arrangements and facades are being simulated. By means of laboratory experiments (i.e. listening tests) it will be investigated and quantified to what extent the building geometry, as well as the facade structure and absorption, influence noise annoyance and acoustic comfort.
Contact: Kurt Eggenschwiler
Partner/Funding: FOEN
Duration: 2019 – 2021

Urban Mining for Low Noise Urban Roads and Optimized Design of Street Canyons
The soundscape of urban situations is often dominated by road traffic noise. In densely populated areas, noise can cause serious health problems and therefore, city planners are seeking for suitable design strategies to improve the acoustical quality of public spaces.
This SNF funded project aims for a multidisciplinary approach to optimize urban roads and street canyon designs. It is structured in four modules:
1) Development of low noise pavements to improve comfort and health of urban dwellers.
2) Identification of waste materials from the urban environment, for the purpose of producing low noise pavements.
3) Exploration of the noise reduction potential by modification of absorption and reflection properties of the surfaces that form urban street canyons and evaluation of the measures from a subjective point of view by auralisation and listening tests.
4) Improvement and extension of existing methods in Life Cycle Impact Assessment based on the results obtained in module 3).
Contact: Kurt Heutschi
Partner/Funding: Empa Road Engineering / Sealing Components Laboratory, ETHZ Ecological Systems Design, SNF
Duration: 2018 – 2021

Acoustic Characterization of fungi-treated Violins
How does a fungi-treatment of the tone-wood affect the acoustic properties of violins? An experimental investigation of the structure-borne and the radiated sound fields of different violins – treated and untreated – is performed in the anechoic laboratories. A subsequent psycho-acoustic investigation focusses on the perception and endeavors to single out significant acoustic properties of the individual instruments.
Contact: Reto Pieren
Partner/Funding: Fischli-Stiftung, Allschwil, CH
Duration: 2017 – 2021

Novel Rail Pads for Improved Noise Reduction and Reduced Track Maintenance
The goal of the project is to develop a novel rail pad system that is optimized with respect to both railway noise reduction and protection of the railway superstructure against transient loads and vibrations. The desired property profile of the novel rail pad cannot be obtained with existing materials, but requires tailoring of the structure and function of the rail pad system at multiple levels and length scales.
We will complement experimental methods with state-of-the-art modelling in order, for the first time, to establish rigorous structure-property relationships, and provide detailed guidelines for combined materials selection and device geometry optimization.
Contact: Bart Van Damme
Partners: École polytechnique fédérale de Lausanne EPFL (LMOM, LPAC, LMAF, LTS2, TRACE), SBB
Funding: FOEN
Duration Phase I: 2017 – 2019
Duration Phase II: 2020 -

ARTEM - Aircraft noise Reduction Technologies and related Environmental iMpact
With ARTEM (Aircraft noise Reduction Technologies and related Environmental iMpact), seven EREA members and strategic partners have teamed up with leading European universities and major entities of the European aerospace industry in order to address the technology challenges raised in the call MG-1-2-2017 “Reducing aviation noise”. ARTEM aims at the maturing of promising novel concepts and methods which are directly coupled to new low noise and disruptive 2035 and 2050 aircraft configurations. A core topic of ARTEM is the development of innovative technologies for the reduction of aircraft noise at the source. The approach chosen moves beyond the reduction of isolated sources as pure fan or landing gear noise and addresses the interaction of various components and sources - which often contributes significantly to the overall noise emission of the aircraft. Secondly, ARTEM addresses innovative concepts for the efficient damping of engine noise and other sources by the investigation of dissipative surface materials and liners. The chosen technology concepts offer the chance to overcome shortcomings (as the narrow band absorption peak or poor low-frequency performance) of current devices. The tasks proposed will mature, and subsequently down select these technologies by comparative testing in a single relevant test setup. Furthermore, noise shielding potential for future aircraft configurations will be investigated. The noise reduction technologies will be coupled to the modelling of future aircraft configurations as the blended wing body (BWB) and other innovative concepts with integrated engines and distributed electrical propulsion. The impact of those new configurations with low noise technology will be assessed in several ways including industry tools, airport scenario predictions, and auralization. Thereby, ARTEM constitutes a holistic approach for noise reduction for future aircrafts and provides enablers for the expected further increase of air traffic.
Contact: Reto Pieren
Project partners: DLR, AEDS, Airbus, CIRA, CNRS, Comoti, Dassault, EC Lyon, EPFL, ONERA, INCAS, PPS, RRD, SAE, SOTON, TSAGI, TUBS, TUDelft, UBristol, UCP, URoma3, VKI
Project funding: EU – Horizon 2020
Duration: 2017 – 2021

TraNQuIL - Transportation Noise: Quantitative Methods for Investigating Acute and Long term health effects
The overall aim of TraNQuIL is to obtain a thorough understanding on how transportation noise affects human health. In particular, the following research questions will be addressed:

  1. How relevant is eventfulness of noise and duration of quiet phases between events for cardiovascular mortality, and adolescents’ cognitive performance, behaviour and quality of life?
  2. How crucial is noise exposure at different times during day and night for these outcomes?
  3. How relevant is noise exposure at home vs. school for adolescents’ cognitive performance, behaviour and quality of life?
  4. Are noise induced cardiovascular risks reversible after noise exposure reduction? If yes, what is the relevant time scale?
  5. Do noise events trigger an acute cardiovascular death?

Research will be based on the existing Swiss National Cohort (SNC) and adolescent HERMES cohort study. Nationwide models for road, railway and aircraft traffic noise as well as NO2 exposure at each address in Switzerland for 2001 and 2011 will be individually linked to study participants. For HERMES participants, a longitudinal analysis will be conducted to evaluate the effects of noise exposure at school and home on changes in cognitive function, behaviour and health related quality of life within one year of follow-up. Full residential history available after 2010 for the SNC will be used to elucidate the effects of a sudden change of exposure on cardiovascular mortality. A case-crossover analysis on the triggering effects of aircraft noise on acute coronary events in the population around Zürich airport will be conducted, taking advantage of the daily distribution and variation of noise exposure which is heavily influenced by meteorological conditions.
Contact: Beat Schäffer
Project partners: Swiss TPH
Project funding: Swiss National Science Foundation
Duration: 2017 – 2021

Noise Protection in Wooden Buildings
Complaints about noise intrusion from neighboring dwellings, especially from people walking, are still a major problem in multi-family wooden buildings.  The goal of the project “Noise Protection in Wooden Buildings” lead by Lignum and in collaboration with Empa and the Bern University of Applied Sciences is to improve acoustic comfort in modern multi-family wooden buildings in Switzerland by generating knowledge on the airborne and impact sound insulation and disseminating it for the engineers and planers.  The role of Empa’s Laboratory of Acoustics/Noise Control within this project is the experimental investigation of sound transmission through building elements and in mock-ups of typical Swiss wooden buildings in the lightweight construction sound transmission research platform and the analysis of the data. Further, Empa post-processes the data for the use as input data for engineering models for the prediction and optimization of airborne and impact sound insulation. Empa derived simplified engineering models from prediction models for heavy construction, such as concrete and masonry that are well established in Europe. These models can be applied by practitioners and engi-neers already in the stage of design of wooden buildings. The project is funded by the “Aktionsplan Holz” of the Swiss Federal Office of the Environment (FOEN) and a consortium of industry partners.
Contact: Stefan Schoenwald
Project partners: Lignum, BFH-AHB, Industriepartner
Project funding: Lignum
Duration: 2016 – 2020

Dr. Reto Pieren

Dr. Reto Pieren
Head of Group Environmental Acoustics

Phone: +41 58 765 6031

Dr. Andrea Bergamini
Head of Group Materials & Systems

Phone: +41 58 765 4424

Dr. Beat Schäffer
Head of Group Noise Impact

Phone: +41 58 765 4737