Click on the title of the talk to read the abstract of each speaker.

Click on the names of the following distinguished keynote speakers for their biography.


Professor Jeremy Astley
ISVR, University of Southampton, UK
'Predicting and reducing aircraft noise'


Professor Ilene Busch-Vishniac
Johns Hopkins University, US
'The challenges of noise control in hospitals'


Associate Professor Svante Finnveden
MWL, Royal Institute of Technology, Sweden
'Two observations on the wave approach to SEA'


Professor Colin Hansen
The University of Adelaide, Australia
'Optimisation of active and semi-active noise and vibration systems'


Professor Jeong-Guon Ih
Korea Advanced Institute of Science and Technology (KAIST), Korea
'Acoustic holography based on the inverse-BEM for the source identification of machinery noise'


Associate Professor Kimihiro Sakagami
Kobe University, Japan
'Recent developments in applications of microperforated panel absorbers'


Professor David Thompson
ISVR, University of Southampton, UK
'But are the trains getting any quieter?'

Professor Jeremy Astley

Professor of Computational Acoustics
Fluid Dynamics and Acoustics Group
ISVR – Institute of Sound and Vibration Research,
University of Southampton, UK
http://www.isvr.soton.ac.uk/STAFF/staff45.htm

'Predicting and reducing aircraft noise'

Air travel in the UK has increased five-fold over the last 30 years. Half the population now flies at least once a year and freight traffic at UK airports has doubled since 1990. Similar statistics hold for other developed countries. It is likely that this growth will be eclipsed in the years to come by the expansion in civil aviation within emerging giants such as India and China.

Civil aviation links distant communities for social and business purposes and gives affordable access to foreign travel for leisure purposes. It is unlikely however that the global community can continue to enjoy the benefits of air travel through increased capacity regardless of environmental cost. To tackle this problem, a balanced approach is essential which recognises the importance of air travel, but which also deals with environmental issues such as noise and emissions. Predicting the effects of noise and emissions is a first essential step towards such a solution. This article focuses on the prediction of aircraft noise and on developing noise reduction technologies.

The aircraft noise issue is that of reducing the environmental impact of exterior noise at take-off and approach. This constitutes a major nuisance to residents near airports. It has resulted in stringent local airport regulations, such as the ‘quota count’ system at Heathrow, which are now more restrictive in defining acceptable limits for aircraft noise than are the international noise regulations promulgated by ICAO which first brought aircraft noise within a regulatory framework in the sixties and seventies.

In this article, the major sources of noise in a modern aircraft are discussed, and current techniques for predicting aircraft noise are reviewed. These include the effects of source definition and acoustic treatment. Recent advances in noise reduction technology will be presented and their performance assessed in the light of noise targets set by the Advisory Council for Aeronautics Research in Europe (ACARE) in their ‘vision 2010’ and ‘vision 2020’ plans. Finally some specific noise reduction technologies will be described which have been developed and assessed in recent EC projects.


Professor Ilene Busch-Vishniac

Mechanical Engineering Department
Johns Hopkins University
Baltimore, Maryland, US
http://www.me.jhu.edu/people/faculty/busch.html

'The challenges of noise control in hospitals'

Over the past few decades, the noise in hospitals has been monotonically rising and is now sufficiently high that speech communication clarity is a concern. The reason hospitals are noisy is clear: the density of people is very high, most of them are ambulatory, and all of them communicate primarily through speech. Add to this mix alarms, a paging system, mandated high rates of air flow and you have a recipe for acoustic pandemonium. Further, the ability to control the noise through traditional approaches, such as sound absorbing material, are limited by hygiene considerations. In this talk we characterize interior hospital noise and discuss approaches to its reduction. Our focus is on noise control strategies that will work long term because they involve objective changes in the facilities and sound environment rather than behavioral changes in people.

Co-author: James E. West


Associate Professor Svante Finnveden

Department of Aeronautical and Vehicle Engineering
Marcus Wallenberg Laboratory for Sound and Vibration Research
Royal Institute of Technology, Sweden
http://www.ave.kth.se/staff/mwl/Svante_Finnveden.html

'Two observations on the wave approach to SEA'

First, an axiomatic demonstration of the wave approach to SEA is presented. This demonstration is most useful for didactic purposes. Also, the explicit statement of the assumptions required for the demonstration implies directions for research as will be discussed. Second, some new results on the evaluation of SEA parameters based on the wave approach are presented. These examples might include the calculation of the radiation efficiency from porous layered structures or a new double wall formulation, dependent on the author’s successes and failures in research during the next few months.


Professor Colin Hansen

School of Mechanical Engineering
The University of Adelaide, Australia
http://www.icsv14.com/hansen.htm

'Optimisation of active and semi-active noise and vibration systems'

Active and semi-active noise control system design may be considered to be multi-variable optimisation processes. The performance of the final design is a function of the order in which various aspects of the design are optimised as well as the optimisation process chosen for each aspect. Here, the optimal hierarchy for control is discussed first of all, followed by a discussion of the optimisation of various aspects of control system design. These aspects include: the physical arrangement of reference sensors, error sensors and control actuators; the choice of cost function; the choice of control system hardware architecture; and the choice of algorithm and associated parameters. The optimisation of these variables will be illustrated with examples of work currently being undertaken by the AVC group at the University of Adelaide.

Co-authors: Xiaojun Qiu, Guillaume Barrault, Carl Q. Howard, Cornelius Petersen and Sarabjeet Singh


Professor Jeong-Guon Ih

Vice President of the Acoustical Society of Korea (ASK)
Center for Noise and Vibration Control (NoViC)
Department of Mechanical Engineering
Korea Advanced Institute of Science and Technology (KAIST)
Science Town, Daejeon, Korea
http://aclab.kaist.ac.kr

'Acoustic holography based on the inverse-BEM for the source identification of machinery noise'

Near-field acoustical holography (NAH) is an indirect method for the identification of vibro-acoustic properties of vibrating sound sources. In this technique, acoustic properties on the source plane can be inversely reconstructed, using the field pressure, which is measured on the measurement or hologram plane. The sound radiation, diffraction and transmission between the vibrating source and the measurement field can be modeled by the vibro-acoustic transfer matrix using the boundary element method (BEM). Consequently, the distribution of the surface velocities of the arbitrary shaped source, not on the near-field 'source' plane, can be reconstructed by multiplying the inverse of the calculated vibro-acoustic transfer matrix and the measured field pressure vector at any shape of near-field plane, including the conformal one. This type of conformal NAH technique has the following advantages compared with conventional NAH based on the spatial Fourier transform: one can deal with the complex shaped sources that cannot be described by separable coordinates; the pressure need not be measured in separable coordinates, thus a reduced number of measurements with uneven spacing is possible; reflections from all directions can be considered; concave regions of the source can be reconstructed; and wrap-around error due to the finite aperture size is not involved. In this talk, the basic nature of the involved problems will be explained and a procedure for realizing the inverse identification of the machine noise source will be demonstrated in several practical applications.


Associate Professor Kimihiro Sakagami

Environmental Acoustics Laboratory
Faculty of Engineering
Kobe University
Kobe, Japan
http://www.arch.kobe-u.ac.jp/~en1/index-e.html

'Recent developments in applications of microperforated panel absorbers'

Microperforated panel (MPP) absorbers are promising as a basis for the next-generation of sound absorbing materials. An MPP was first proposed by D-Y Maa who developed its theoretical basis as well (eg. D-Y Maa: Theory and design of microperforated panel sound-absorbing constructions, Scientia Sinica, 1975; 18: 55-71). Its applications, improvement and theoretical development have since been studied extensively. Basically it is backed by an air-cavity with a rigid-back wall, and its typical use is for a sound-absorbing ceiling. However, MPPs have some limitations and disadvantages: its sound absorbing mechanism is limited to a Helmholtz resonator caused by perforations with air-cavity, and effective absorption is limited to the resonance frequency range. There is also a problem when we use an MPP for sound absorbing finish of room interior surfaces, because typical MPPs are made out of thin limp materials and not strong enough. In order to solve these problems, in our research project on the application of MPPs for building purposes we have studied the following:

1. Application of MPPs for room interior surfaces It is needed to make an MPP strong enough for room interior surfaces. However, if a thick material is used to make MPPs strong, the acoustic performance will be deteriorated due to its excess acoustic resistance and reactance. Thin MPPs are advantageous to produce optimal acoustic resistance and reactance. Therefore, it is important to make MPPs strong enough without deteriorating the acoustic performance.

In our project, the following treatments were considered, and their acoustical effects were discussed: (1) using an elastic support to stiffen an MPP, (2) thickening an MPP to make it firm enough, and (3) attaching a honeycomb structure to MPPs to stiffen the construction. Among these three treatments, the honeycomb structure shows interesting effect which makes resonance absorption shift to lower frequencies and more significant. This effect can be useful not only to stiffen an MPP but to improve it also. Regarding thickening MPP, a trial production of thick MPPs were carried out, and we found that there is a possibility to obtain reasonably good absorption performance with thick MPP by changing the profile of perforation.

2. Multiple-leaf MPP absorbers A permeable material is known to cause sound absorption by their acoustic flow resistance. Its typical example is a single- or multiple-leaf permeable membrane. The similar absorption effect can be expected as an MPP can also be regarded as a permeable material with acoustic flow resistance. In this study, to create an efficient sound-absorbing structure with MPPs alone, a double-leaf MPP (DLMPP) is proposed and studied theoretically. A DLMPP is composed of two MPPs set in parallel with an air-cavity in-between without a rigid back wall. In this structure, the MPP on the back side plays the role of the back wall in the conventional setting to cause the resonance-type absorption. Additionally, a DLMPP can have high absorptivity on both sides to work efficiently for sound incidence from both sides, and can be efficiently used as space absorbers.

The results show (1) that the resonance absorption similar to the conventional type MPP absorbers appears at middle-high frequencies, and (2) that considerable additional absorption can be obtained at low frequencies. This low-frequency absorption is similar to that of a double-leaf permeable membrane, and can be of advantage over the conventional type. A parametric study for optimal design of DLMPP is presented, and as a further possibility, a triple-leaf MPP absorber is briefly discussed.


Professor David Thompson

Professor of Railway Noise and Vibration
Dynamics Group
ISVR – Institute of Sound and Vibration Research
University of Southampton, UK
http://www.isvr.soton.ac.uk/STAFF/staff3.htm

'But are the trains getting any quieter?'

To reduce railway noise effectively a good knowledge of the source mechanisms is first required. Wheel/rail interaction in particular results in a multiple source environment where wheels, rails and sleepers all play a role. This is a classic noise control problem where treatments will not be successful unless they take account of the relative importance of each source and apply appropriate measures for all the significant sources. Starting from theoretical research into source modelling, a number of practical techniques have been developed for reducing railway noise in the last 10-20 years, which will be discussed. While focussing on rolling noise, the related problems of curve squeal, bridge noise, aerodynamic noise and vehicle interior noise will also be mentioned. Finally it is recognised that the railway industry faces many pressures that make it reluctant to change, so the difficulties of practical implementation will be discussed.