Periodicity-Enhanced Attenuating Layers and Structures

Lead Research Organisation: University of Salford
Department Name: Sch of Computing, Science & Engineering

Abstract

Periodicity-enhanced (meta) materials and surfaces are artificial structures that possess properties not found in naturally-occurring materials and surfaces. The periodicity stems from the regular spacing of inclusions in a host matrix or roughness on a surface. Inclusions range from solid cylinders in air such as encountered in 'sonic crystals' to a grid framework in a poroelastic material such as an air-filled foam used for sound absorption. Roughness elements can be of various shapes and profiles ranging from identical rectangular grooves to arrays with fractal profiles. Without further modification, periodicity-enhanced materials stop the passage of some incident wavelengths (or frequencies) and enhance the transmission of others. By modifying the roughness of a surface, the interference between waves travelling directly from a source to a receiver above the surface and waves reflected from the surface can be controlled.
The proposal is concerned with ways of extending the frequency range over which the periodicity-enhanced materials and surfaces reduce the transmission of sound and vibration. The methods to be investigated include use of locally resonant inclusions or roughness elements, use of multiple resonances, exploitiation of interactions and overlaps between resonances periodicity-related transmission loss and spatial variation of periodicity and other characteristics thereby producing graded systems and roughness profiles. The work will provide a basis for the design of more efficient sound and vibration absorbing devices that are lightweight yet offer high transmission loss and vibration damping properties. The resulting surface designs will include alternatives to conventional noise barriers, while allowing access and preserving line of sight, and cost-effective methods for protecting buildings against ground-borne vibrations.
 
Description We have discovered that
1. A method of multi-scale homogenization can be used to derive a simple expression for the admittance of a resonant metasurface. At the leading order, this is described by a simple analytical expression, while at the corrector order a non-local nature of admittance has to be accounted for.
2. A total absorption of incident sound can be achieved with a finite size metasurface around the resonance frequency of the unit cells. The phenomena are quite robust and good absorption is achieved even when the incident wave is not plane.
3. Mixing slightly mistuned resonators in a single cell broadens the frequency range where high absorption values are achieved. The interaction between the resonators can be described as a part of the homogenization procedure.
4. We have shown that graded surfaces, certain surfaces with several resonators per period and corrugated
5. It has been demonstrated numerically and experimentally that the metasurface is efficient for cavity mode control.
6. Another part of work has been devoted to the interaction of resonators in a single unit of a metamaterial and the interaction between the resonators and the substrate. It has been shown that the resonance frequency can be controlled by rotating the resonators. The lowest frequency is achieved when the slots are facing each other or when the slot is facing the substrate.
7. Effective boundary conditions become non-local when surface properties are graded and when the surface is corrugated. In these cases, the non-locality appears in the corrector order derivations over the smallness parameter identified as the ratio of lattice constant to the wavelength at resonance.
Exploitation Route We expect, the results will attract an interest from the research community. We expect that the method of multi-scale homogenization will find a wide application for modelling properties of metasurfaces and metamaterials. This should include the cases when the contrast between the scales is not high, so accounting for corrector order terms in the homogenization procedure becomes necessary. The model developed can be used as a design tool for building metasurfaces with prescribed acoustic properties.
Sectors Aerospace, Defence and Marine,Construction,Transport,Other

URL http://www.sciencedirect.com/science/article/pii/S0165212517300161
 
Description The findings of this project have been already used for 3 BSc, 1MSc and 1 MRes projects at the University of Salford. A collaboration with the industry (Carbon Air Ltd, DSTL UK) is developing -the elements of metasurface design and modelling will be used for the development of new structures/ products. A KTP project with Cosmotec Textiles (funded by Innovate UK) has been successfully completed in 2019. The work on developing new product ideas was based on the findings of Periodicity Enhanced Attenuating Layers and Structures project. In particular, near field interactions between the fibres within the nonwoven materials have been used to enhance their sound absorption capacity.
First Year Of Impact 2016
Sector Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software),Education,Manufacturing, including Industrial Biotechology,Transport
Impact Types Economic

 
Description Vice-chair and member of the COST Action DENORMS CA 15125
Geographic Reach Europe 
Policy Influence Type Influenced training of practitioners or researchers
Impact COST Action DENORMS CA 15125
URL https://denorms.eu/
 
Description DSTL-DGA Anglo-French PhD studentship, project title "Acoustic metamaterials for harsh environments"
Amount £128,849 (GEL)
Organisation Defence Science & Technology Laboratory (DSTL) 
Sector Public
Country United Kingdom
Start 09/2017 
End 04/2019
 
Description Poroelastic metasurface for simultaneous attenuation of airborne sound and vibrations
Amount £52,000 (GBP)
Organisation University of Salford 
Sector Academic/University
Country United Kingdom
Start 09/2019 
End 10/2022
 
Description Senior Visiting Researcher, University of Burgundy
Amount € 4,000 (EUR)
Organisation University of Burgundy 
Sector Academic/University
Country France
Start 05/2014 
End 07/2014
 
Description Visiting researcher grant, University of Burgundy, France
Amount € 6,000 (EUR)
Organisation University of Burgundy 
Sector Academic/University
Country France
Start 05/2018 
End 08/2018
 
Title Measurement data on absorption of metasurface in anechoic environment 
Description Measurement data on the performance of resonance metasurface in anechoic environment collected at Salford University in November - December 2015. 
Type Of Material Database/Collection of data 
Provided To Others? No  
Impact The data generated confirm that full absorption at resonance frequency can be achieved by a finite size metasurface even when the incident wave is not plane 
 
Title measurement data on the performance of metasurface in the impedance tube 
Description The experiments have been performed at Salford University confirming the design approach to achieve the full absorption at resonance frequency and in the frequency band centred at it. the experiments have been performed using Salford University impedance tube. 
Type Of Material Database/Collection of data 
Provided To Others? No  
Impact The design approach developed by the group has been confirmed by the measurements performed using impedance tube. This is the simplest and most controlled environment for acoustic experiments. The measurements have been performed on a number of identical basic elements of the metasurface as well as a mixture of elements with different resonance frequencies. A very good agreement with the model has been observed. 
 
Description C. Boutin ENTPE, France, 
Organisation University of Lyon
Department National School of Public Works of the State
Country France 
Sector Academic/University 
PI Contribution Contribution to collaboration from Salford: Multiple scattering, Experiments, development of homogenization technique in application to acoustic metasurfaces
Collaborator Contribution Contribution to collaboration from ENTPE: Two -scale asymptotic homogenization technique
Impact Several papers listed in the Publications section have been written in collaboration with C.Boutin
Start Year 2014
 
Description DSTL 
Organisation Defence Science & Technology Laboratory (DSTL)
Country United Kingdom 
Sector Public 
PI Contribution The models and the devices/ structures developed during the project
Collaborator Contribution Testing facilities, advice on the use of the project outcomes for military applications
Impact The collaboration is still in its early stage so there are no any particular outcomes yet
Start Year 2014
 
Description University of Burgundy, France 
Organisation University of Burgundy
Country France 
Sector Academic/University 
PI Contribution An analytical model has been developed by O.U. for a joint paper published in Journal of the Acoustical Society of America in October 2015
Collaborator Contribution A numerical model and experiments for this paper have been performed by research team in ISAT, University of Burgundy, France
Impact A joint paper has been submitted to Journal of the Acoustical Society of America A joint PhD project with ISAT has started in October 2016
Start Year 2014
 
Description collaboration with LAUM, University of Maine, France 
Organisation University of Maine
Country United States 
Sector Academic/University 
PI Contribution Analytical models edeveloped by O.U. have been published in two joint papers. O.U. lead a submission of COST proposal in 2013 (unsuccessful), which was prepared in collaboration with research team from LAUM.
Collaborator Contribution Numerical models. COST proposal has been prepared jointly.
Impact Two joint research papers published in 2013. COST grant proposal in 2014 (unsuccessful).
Start Year 2012
 
Description COST Action DENORMS CA 15 25 workshop 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Logan Schwan and Olga Umnova are engaged with COST Action DENORMS CA 15 25 project: O.U. as a co-chair and L.S. as a regular member. They participated in the 1st DENORMS workshop held in Jan 2017 in Rome. The audience mostly comprised of PhD students, early career researchers and industrial partners.
Year(s) Of Engagement Activity 2017
URL https://denorms.eu/2016/09/28/workshop/
 
Description paper in a professional magazine 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact A paper is published in Issue 82, 2016 of La revue Acoustique & Techniques, entitled Contrôle des vibrations par surfaces résonantes : Exemples en acoustique et en élastodynamique by L.Schwan, C.Boutin, O.Umnova and M.Dietz.
Year(s) Of Engagement Activity 2016