Plenary Keynote Lectures
The Congress Programme will include distinguished Plenary Keynote Lectures by
Prof. Jorge P. ARENAS
Institute of Acoustics
Universidad Austral of Chile
Sound Barriers and Environmental Impact Studies
In particular, noise barriers are a commonly used measure to reduce the
high levels of environmental noise produced by the traffic on highways.
Nevertheless, single screen barriers are also widely used in open-plan
offices to separate individual workplaces in order to improve acoustical
and visual privacy. When developing environmental impact studies for
highways, it appears that construction of barriers is the main alternative
used for the reduction of noise, although quiet road surfaces, insulation
of properties or use of tunnels have also been used for this purpose. In
the design of a barrier all of the relevant environmental, engineering and
safety requirements have to be considered. However, in addition to mitigate
the impact of a highway, a barrier will become part of the landscape and
neighbourhoods. The public, increasingly well-informed about the problem of
excessive noise, is taking actions on the development of new transport
infrastructure projects and improvement to existing infrastructure.
Therefore, particular consideration has to be taken to assure a positive
public reaction from both residents adjacent to barriers and drivers. In
this keynote lecture a review of some fundamentals of the theory of the
diffraction at the edge of a plane barrier will first be considered as the
basis for all applications and the development of prediction algorithms.
Then, use of barriers indoors and outdoors will be presented. Finally, some
additional concepts for the design, economics, materials, construction
details, aesthetic, and durability will be discussed.
Prof. Voichita BUCUR
INRA - Centre de Nancy
LERMAB (Laboiratoire Etudes et Recherches sur le Materiau Bois)
Acoustics of Wood
This lecture presents several acoustic methods effective for examining physical properties of wood, as a living material. Three main aspects are commented:
For efficient use of wood in the future three major areas need to be addressed: the development of efficient nondestructive techniques, the improvement of natural qualities of wood through the modification of its properties with different treatments, and the development of new products corresponding to the requirements of modern society.
Prof. Hugo FASTL
AG Technical Acoustics,Institute for Human-Machine Communication
Technical University Munich
Psychoacoustic Basis of Sound Quality Evaluation and Sound Engineering
In R & D departments of companies, the evaluation of sounds usually
is based on physical measurements. However, in "real life", the ultimate
judge for sounds is the human hearing system. A customer evaluates the
sound of a product by his or her hearing system, not by physical
measurement tools, whatever their sophistication may be. In this situation, psychoacoustics is the scientific field of choice to bridge the gap between physical and subjective evaluations. In psychoacoustic experiments, firm relations between the physical representations of sounds and the correlated hearing sensations are established.
In practical applications of psychoacoustics, two main tasks can be distinguished:
First, questions of sound evaluation, usually for already existing sounds which often have to be improved and
Second, questions of sound quality engineering, where for a (new or modified) product or application a suitable sound has to be "tailored".
For the evaluation of sounds, basic psychoacoustic magnitudes like loudness and sharpness have proven successful, which assess volume or power and tone colour of sounds, respectively. Using these descriptors, extremely different questions like the quality of piano sounds or the annoyance of snoring sounds can be assessed. In addition, psychoacoustic magnitudes related to the temporal structure of sounds like fluctuation strength or roughness can play an important part.
In sound quality engineering, for each sound, the right "recipe" has to be found, how to mix the different hearing sensations, to arrive at the desired sound. For the example of warning signals, a systematic approach, incorporating elements of decision tree studies, is discussed.
Prof. Daniel J. INMAN
Center for Intelligent Material Systems and Structures, Department of Mechanical Engineering
Active and Passive Damping of Structures
Modern structures are often driven by design constraints to be extremely lightweight and hence very flexible and subject to increased vibration problems. In addition, improved manufacturing techniques often produce very good joints in structures reducing the amount of natural damping in structures. For instance, removing welds in bladed disc assemblies caused increase blade fatigue because of the reduced damping. As a result, active and passive damping methods are increasingly in demand. Here the basic areas of passive and active damping are reviewed and compared. Emphasis is placed on damping treatments, smart materials and applications to large flexible (inflated) space structures and automobile components.
Passive methods discussed include a summary of standard constrained layer damping treatments and piezoelectric based shunt dampers with focus on the various modeling methods and comparisons. Active methods focus on those that are obtained by using piezoelectric based materials: films, ceramics, and composites, as the sensor and actuation devices. The main example consists of a 300 meter/ 552 kg inflated satellite proposed for flight in the next 10 years called the Innovative Space Based Radar Antenna Technology (ISAT) program. This truss like structure holds a radar platform and is intended to rotate around its mid point for surveying the earth’s surface. The rotation along with other maneuvering forces potentially causes large vibration interfering with the satellites ability to take measurements. Hence, active vibration means are required to remove these unwanted vibrations. Theoretical and numerical results are presented along with experimental validations of the modeling and vibration suppression methods.
Prof. Hiroshi WADA
Department of Bioengineering and Robotics
Recent Findings on our Auditory System: It is Very Sensitive Owing to the Motility of Sensory Cells
The ears are paired sense organs, which collect, transmit, and detect acoustic impulses. Each of them is comprised of three main parts: the outer ear, middle ear, and inner ear. Traveling sound is focused into the external auditory canal by the pinna, causing vibration of the tympanic membrane and motion of the three ossicles in the middle ear. Their motion is transmitted to the cochlea of the inner ear. The mechanical motion of the basilar membrane in the organ of Corti is then transduced into encoded nerve signals in the cochlea, which are transmitted to the brain.
Even though the amplitude of tympanic membrane vibrations is only a few nanometers when we speak in a low voice, we can clearly understand what is
being said. This is due to cochlear amplification caused by the motility of outer hair cells (OHCs), which are located in the organ of Corti of the ochlea.
The origin of this motility is believed to be associated with a membrane protein in the lateral wall of OHCs. The gene that codes for this protein has been identified and termed 'prestin.' Prestin has been found to be a direct voltage-to-force converter, which can operate at microsecond rates.
In my talk, firstly, actual measurement results of the tympanic membrane vibrations will be shown by video. Secondly, a dynamic animation of how the middle ear and cochlea function will be presented. Thirdly, the motility of the isolated OHC will be demonstrated, and the function of the OHCs, which behave like actuators of mechanical structures, will be discussed. Finally, images of prestin obtained by an atomic force microscope will be displayed.
Prof. Semyung WANG
Department of Mechatronics
Gwangju Institute of Science and Technology (GIST)
Compressor Noise Control
Compressors are main components of refrigerators and air-conditioning systems for home and cars. Since customers are asking lower noise and lower power consumption, compressors should be designed with noise control and efficient motors.
In this talk, noise control of several compressors such as reciprocating, linear, rotary, and scroll compressors is introduced. For those compressors noise source, noise path, and noise generation are explained with experimentally and numerically. Finally design optimization of compressors for noise reduction is given.
Prof. Franz ZIEGLER
Institute for Building Construction and Technology, Center of Mechanics and Structural Dynamics
Vienna University of Technology
The Tuned Liquid Column Damper as the Cost-effective Alternative of the Mechanical Damper within Vibration Prone Civil Engineering Structures
Modern architecture, limited space in urban area and new developments in building construction techniques have caused an increased need to construct flexible and tall structures. However, many of those structures are vibration prone and even minor dynamic loads like regularly occurring wind gusts may cause occupant discomfort, especially in the upper floors of high-rise buildings. On the other hand, earthquakes and strong winds often cause structural damage or even failure and thus an increased awareness about the vulnerability of modern structures became public. These include large dams and all kinds of light bridges from footbridges to long-span bridges with the need of increased effective structural damping. In the course of the cantilever method of bridge construction, critical states are encountered in windy situations. Consequently, there is a higher demand to protect the structures from all kinds of dynamic loads. Damping in the low frequency range of such vibration prone C.E. structures requires a concentration of energy for its efficient dissipation. The classical tuned mechanical damper (TMD) requires high investments and maintenance fees. In all respects, the tuned liquid column damper (TLCD) is superior, and it is analyzed and, in a first step modally tuned, using a recently established geometrical analogy to the TMD. When sealed, choosing the right gas pressure in chambers above the liquid surface extends the frequency range of application from close-to-zero to about five Hertz. The slightly over-linear gas-spring effect in combination with the averaged turbulent damping of the (relative) fluid flow (verified experimentally), protect the TLCD from overload by detuning. Fine-tuning in state space improves the performance even further. Fuzzy stiffness can be accounted for in the design stage. The result is a robust control in the frequency window around a resonance of the main structure with its effective structural damping dramatically increased.