Upcoming Events

Signal procession for Sound — 13, 14 February 2012

These two events are being organized by the IEEE New Zealand Central Section
Joint Chapter on Signal Processing, Communications and Information Theory

Speaker: Professor Steve Elliott         Institute of Sound and Vibration Research         University of Southampton,         Southampton SO17 1BJ, UK. Venue: Victoria University of Wellington, Cotton Building, CO 350 Topic 1: FEEDBACK CONTROL OF VIBRATION IN AIRCRAFT AND IN THE EAR Date  1: Monday 13 Feb 2012 Time  1: 1:10 pm Topic 2: PERSONAL AUDIO AND ACTIVE CONTROL OF SOUND IN THE ENVIRONMENT Date  2: Tuesday 14 Feb 2012 Time  2: 9:00 am ---------------------------------------------------------------------- Abstract 1: The low frequency sound and vibration inside aircraft is now _attenuated_ using commercial active control systems. These typically operate using many shakers acting on the structure to modify its vibration and hence reduce excitation of the sound field. As the structure becomes larger, the number of actuators and sensors required for effective control rises significantly. Conventional, fully coupled, control systems then become costly in terms of weight and sensitivity to individual failures. An alternative strategy is to distributing the control over multiple local controllers, which has been shown to be effective in a number of cases. Recent work will be presented on tuning these local control loops to maximise the power they absorb from the structure, which may allow the mass production of generic active control modules that include an actuator, sensor and self-tuning controller. The workings of the inner ear also provide a remarkable natural example of distributed active vibration control, whose objective is to _enhance_ the motion within the cochlea. A simple model for this cochlear amplifier, in which each of the outer hair cells act as local control loops, will be described and its use illustrated in predicting the otoacoustic emissions generated by the ear. These emissions are used clinically to screen the hearing of young children and so it is important to understand how they are generated within the cochlea. ---------------------------------------------------------------------- Abstract 2: As well as being able to reproduce sound in one region of space, it would be useful in many applications to be able to control the level of reproduced sound in other spatial regions. This is motivated by issues of privacy for the user and the need to reduce annoyance for other people nearby. The techniques for implementing this kind of "personal audio" using array of loudspeakers have much in common with systems for the active control of sound, where the traditional objective has been only to reduce the sound level in environments such as cars and aircraft, for example. Several practical examples of personal audio systems will be described, including using an array of loudspeakers in headrests to reproduce separate audio channels in adjacent seats, a system to reduce radiated sound from hands-free mobile devices and zonal amplification of TV audio. These systems often have a fundamental trade-off between performance and array effort, where the latter affects both the electrical power requirements of the array and its robustness to variations in driver response. Signal processing strategies will be described that allow a good compromise to be drawn between these competing requirements. ---------------------------------------------------------------------- Presenter Biography: Steve Elliott graduated with first class joint honours BSc in physics and electronics from the University of London, in 1976, and received the PhD degree from the University of Surrey in 1979 for a dissertation on musical acoustics. After a short period as a Research Fellow at the ISVR and as a temporary Lecturer at the University of Surrey, he was appointed Lecturer at the Institute of Sound and Vibration Research (ISVR), University of Southampton, in 1982.  He was made Senior Lecturer in 1988, Professor in 1994, and served as Director of the ISVR from 2005 to 2010.  His research interests have been mostly concerned with the connections between the physical world, signal processing and control, mainly in relation the active control of sound using adaptive filters and the active feedback control of vibration.  This work has resulted in the practical demonstration of active control in propeller aircraft, cars and helicopters.  His current research interests include modular systems for active feedback control and modelling the active processes within the cochlear. Professor Elliott has published over 200 papers in refereed journals and 400 conference papers and is co-author of Active Control of Sound (with P A Nelson 1992), Active Control of Vibration (with C R Fuller and P A Nelson 1996) and author of Signal Processing for Active Control (2001). He is a Fellow of the Acoustical Society of America, the IET and the IOA and a senior member of the IEEE.  He was jointly awarded the Tyndall Medal from the Institute of Acoustics in 1992 and the Kenneth Harris James Prize from the Institution of Mechanical Engineers in 2000. He was made a Fellow of the Royal Academy of Engineering in 2009