Projects

Conventional porous materials are commonly used as sound absorbing materials for passive noise control engineering. These range from various asbestos-based materials to synthetic and natural fibres such as ceramic, mineral wool, fibre glass, glass wool, polyester, cotton, wood fibre, vegetable fibre, and coir fibre. These materials are useful for mid-to-high frequency noise absorption in applications such as automotive, aircraft, spacecraft and ships, due to their effectiveness, low weight and ease of installation. However, these materials have two major drawbacks: they can only absorb low frequency noise with thick material which has a weight penalty, and they have also a short useful life. These drawbacks are forcing acoustic researchers to look for new sound absorbing materials.

Advances in nanotechnology have provided acoustic researchers with a new material known as carbon nanotubes that can potentially be implemented as an acoustic porous absorber. The molecular behaviour of this nano material may have a significant influence on its sound absorption; in addition, its properties could play an important role in reducing the absorber thickness compared to currently available materials. However, the absorption mechanisms of nanoscopic fibres are not fully understood and the application of numerical and analytical modelling methods to this problem is still at an early stage.

This project intends to investigate the absorption characteristics of carbon nano tubes (CNTs) and develop an acoustic absorber based on that knowledge. This task involves undertaking a thorough investigation of the mechanisms of acoustic absorption at the nano-scale to develop a greater understanding of the controlling parameters for absorption relative to the wavelength of sound over a range of frequencies, and a range of sound pressure levels. As the dimension of this material (diameter: 10 to 50 nm and average length: 3 to 10 microns) is in the nano-scale range, the acoustic absorption mechanisms are thus likely to deviate from the continuum phenomena and modelling approaches applicable to flow associated with larger scale fibres.