ISVR-FDAG-130: Acoustic Characterisation of Materials with Complex Structure

Anechoics and isolators are used in underwater acoustic systems to reduce reflections or provide attenuation of sound waves. A range of new innovative materials, known as metamateraials, which have properties not found in natural materials, offer exciting promise for these applications. However, these are typically composite materials with a complex internal structure. Testing the performance of these materials presents new challenges which will be the subject of this project. The classic method of characterising the acoustic transmission and reflection properties of underwater materials using an impedance tube is not suitable as this requires cutting the material. An alternative approach, that has been used very successfully for homogeneous materials, is to use a parametric array to generate a beam with a reasonably small cross-sectional area that enables small planar samples to be tested. However, the testing of new innovative materials, such as metamaterials, will raise particular problems as the materials are likely to have a pronounced internal structure on a scale less than a wavelength resulting in a complex near-field in the vicinity of the panel. This will make the use of traditional measurement techniques inappropriate and hinder the development of such materials. This project will investigate techniques of characterising the 2D field in a plane close to test panel and the use of near-field holography techniques to extract the far-field plane wave behaviour. Possible optical measurement approaches using a Laser Doppler Vibrometer will also be considered. The project will involve a mixture of theoretical modelling, experimental measurement and signal processing. The work will be performed in collaboration with external organisations.

Applicants should have a good first degree in a relevant science or engineering subject. Ideally the candidate will have some experience in acoustics and signal processing as well as numerical modelling. Full funding is available to successful UK nationals.

If you wish to discuss any details of the project informally, please contact Prof Victor Humphrey, Acoustics research group, Email: [Email Address Removed], Tel: +44 (0) 2380 59 4957.