Project outline
Cross-laminated timber (CLT) is increasingly used in multi-storey construction as a lower-carbon alternative to reinforced concrete and steel. Timber is renewable, stores biogenic carbon until its end-of-life, and enables efficient prefabricated construction. However, acoustic performance remains an important challenge, particularly in residential buildings.
Compared with heavyweight construction, timber floors can exhibit poorer low-frequency sound insulation, especially for impact excitation such as footfall. Studies have shown that frequencies below the conventional 100 Hz assessment range, and in some cases as low as 20–25 Hz, can be important to occupants’ perception of sound in timber buildings [1-2]. In addition, the strong orthotropy of CLT and the cellular nature of platform construction create complex vibration and flanking transmission paths through panel junctions and connections [2-4].
Current acoustic solutions typically rely on floating floors, elastomer layers, heavy concrete toppings and suspended ceilings [2-4]. Although effective at mid and high frequencies, their performance is reduced at lower frequencies, and they increase structural mass, construction depth and material use [1]. Recent research has highlighted several promising routes for improving the intrinsic acoustic performance of CLT, including the use of alternative timber species, modified lamella orientations, damping interlayers and other engineered panel configurations [1]. Emerging concepts such as acoustic metamaterials also offer opportunities to control structural vibration and sound transmission through tailored material architecture [5], potentially improving low-frequency performance without relying solely on additional mass. These developments provide a strong basis for exploring new multifunctional CLT systems that combine acoustic, structural and sustainability objectives.
The aim of this PhD is to develop acoustically engineered mass-timber panels with enhanced intrinsic airborne and impact sound insulation, reducing reliance on secondary acoustic treatments. The project will combine finite-element modelling, optimisation and experimental validation.
Further project information
The key research question to be addressed is: Can we improve the intrinsic acoustic properties of Cross Laminated Timber (CLT) by material and geometry optimisation?
The key objectives of this project are to:
- Optimise CLT lay-up geometry, lamella orientation and material selection, including higher-density timber species and bio-based compliant or viscoelastic interlayers such as cork.
- Develop integrated bio-based metamaterial concepts, for example using laser-cut MDF or additively manufactured bio-based resonators, to achieve targeted broadband attenuation.
- Undertake multi-objective optimisation considering acoustic, structural and fire performance, manufacturability, cost, added mass and environmental impact.
- Experimentally test and validate the most promising panel configurations for airborne and impact sound performance.
- Extend the study to representative T- and X-junctions to quantify flanking transmission and the influence of connections and resilient interfaces.
The project combines Finite Element Analytical Tools with experimental methods (airborne sound insulation and rubber ball test) for an integrated design and validation approach.
The project will establish design principles for multifunctional CLT panels in which acoustic performance is treated as an intrinsic material and structural property, supporting lighter, lower-carbon and more acoustically robust timber buildings.
In-kind contribution with materials and additional consulting support can be provided by existing partners (Stora Enso – CLT manufacturer – Objective 4, and Rothoblass – timber fastener manufacturer and acoustic linings – Objective 5).
References:
- Ljunggren, F. (2023) ‘Innovative solutions to improved sound insulation of CLT floors’, Developments in the Built Environment, 13, 100117.
- Di Bella, A. and Mitrovic, M. (2020) ‘Acoustic characteristics of cross-laminated timber systems’, Sustainability, 12, 5612.
- Caniato, M., Bettarello, F., Ferluga, A., Marsich, L., Schmid, C. and Fausti, P. (2017) ‘Acoustic of lightweight timber buildings: A review’, Renewable and Sustainable Energy Reviews, 80, pp. 585–596.
- Ljunggren, F., Fredriksson, M., Johansson, N. and Kalagasidis, S.A. (2026) ‘Cross-laminated timber: a state-of-the-art review of moisture, fire, acoustics, and energy-related aspects’, Wood Material Science & Engineering, 21(2), pp. 1224–1246
- Giannini, D., Van Belle, L., Deckers, E. and Reynders, E.P.B. (2026) ‘Design and validation of a multi-modal resonant metamaterial for broadband sound insulation improvement in orthotropic panels’, Mechanical Systems and Signal Processing, 258, 114650.
Required technical skills/academic qualifications/experience
- Applicants with a 2:1 or higher undergraduate degree or a relevant Master’s degree in civil/structural engineering, mechanical engineering, acoustics, materials engineering, timber engineering, or a closely related discipline are encouraged to apply.
- A good foundation in structural mechanics, dynamics and/or vibration.
- Prior experience in numerical modelling, e.g. Finite Element Modelling, and experimental methods would be advantageous.
- Prior experience with timber, Cross Laminated Timber (CLT), acoustics, metamaterials, optimisation or signal processing would be advantageous, but is not required.
- Strong analytical and problem-solving skills.
- Good written and verbal communication skills.
We particularly encourage applications from women and other groups under-represented in research. All appointments will be made on merit.
Mode of attendance
Successful applicants are expected to register as full-time students. However, eligible UK home fees applicants may request to be considered for part-time attendance by the supervisory team.
Supervisors
Project Partners
This project is hosted at the University of Bristol and supported by Stora Enso and Rothoblaas.
