London Branch

Sonic crystals, metamaterials, acoustic cloaking and black holes

Presentation by Keith Attenborough

Tuesday 24^th June 2014 at 6 pm

WSP, WSP House, 70 Chancery Lane, London, WC2A 1AF

Have you heard about optical structures that can make objects invisible? Have you wondered if similar things can be done with sound, for example, to make a noise source inaudible, even at low frequencies without using heavy enclosures or barriers? Bragg (multiple) scattering in periodic arrays of cylinders gives rise to reduced transmission at some frequencies (called stop bands or band gaps) and enhanced transmission (called focussing or pass bands) at other frequencies depending upon the centre-to-centre spacing of the cylinders (the lattice constant) and cylinder radius (which together with the lattice constant determines the filling fraction). By working with regularly-spaced (often cylindrical) inclusions in air or in a solid is possible to design artificial structures with acoustical properties not found in naturally-occurring or in other man-made materials. This often requires making the inclusions resonant. After outlining underlying physical principles, the talk will focus on two applications of periodic structures for noise control. These are sonic crystal barriers and metasurfaces for enhanced ground effect.

The closest underground stations are Chancery Lane (Central line) and Holborn (Central & Piccadilly line).

For more details of Regional Branch activities please refer to the IOA website: www.ioa.org.uk

Topics and speakers for the evening meetings are generally identified and organised by the London Branch Committee, but we always welcome new ideas and suggestions for future presentations. If you have any ideas or suggestions, or may even like to give a presentation yourself, please contact the London Branch Committee (Nicola Stedman-Jones: stedmann@rpsgroup.com or nathan-nicola@talktalk.net).

The evening meetings are free and there is no need to book a place (except for the annual events, such as the half-day visit and dinner).  The evening meetings are open to members and non-members.