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CASE STUDIES IN INDUSTRIAL NOISE CONTROL

A.R. Mohanty
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Dr. A. R. Mohanty is a professor of Mechanical Engineering at the Indian Institute of Technology, Kharagpur, India where he also holds the Shyamal Ghosh and Sunanda Ghosh Chair Professor position. Professor Mohanty obtained his PhD in the areas of Noise Control from the University of Kentucky, USA. He was also a post doctoral fellow at the Ray W. Herrick Labs of Purdue University, USA working in the areas of active control of tire noise. Professor Mohanty has worked in NVH areas at Ford Motor Company in Dearborn and Larsen & Toubro Limited, Mumbai. He has been a consultant to more than a 100 companies in the areas of noise control and machinery condition monitoring. His research interests are in the areas of machinery condition monitoring, industrial noise control and acoustical materials. Dr. Mohanty has more than 200 refereed journal and conference publications; he has one book, five book chapters and one patent to his credit. He has held visiting faculty positions at universities in the USA, France and Singapore. Professor Mohanty is a fellow of the Indian National Academy of Engineering, Acoustical Society of India, Condition Monitoring Society of India, Institution of Engineers India and the International Society of Engineering Asset Management. He has received several national and international awards and scholarships for recognition of his research and teaching.

Mechanical Engineering
Indian Institute of Technology Kharagpur
India

The speaker would present several case studies in industrial noise control from over three decades of research, teaching and consulting experience both in India and abroad. The case studies would be from the sectors of transportation, machineries and environment. In particular, the successful noise reduction in the driver's cabin of a diesel locomotive for the Indian railways would be presented. From the automobile and mining sector, case studies of application of basic vibration reduction techniques to improve the noise vibration and harshness performance of power trains and cabin noise in automobiles and earth moving machinery operator's cabin will be presented. Results from a research study on the active noise control of tire noise in an automobile would be presented too. Some innovative use of engineered natural materials, on-site novel measurement techniques, state-of-the art analysis technique and instrumentation currently used for noise source identification and its control will be discussed. The application of natural materials for noise reduction in refrigerators, vacuum cleaners and clothes dryer would be presented. The significance of few sound quality metrics in designing quieter machinery components, in particular automobile silencers would be demonstrated from results of a jury evaluation. Some case studies on environment noise control for mining and steel plants would also be presented. An example from underwater noise monitoring during piling operations for establishing safe levels for protection of marine animals during expansion of a shipping jetty would be discussed. Recent developments in the areas of sonic crystal and micro-perforates for application in noise control would be presented.



CHALLENGES AND STRATEGIES ON DYNAMICS PROBLEMS IN CHINESE HIGH-SPEED RAILWAYS

Wanming Zhai
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Professor Wanming Zhai is an Academician of Chinese Academy of Sciences (CAS). He graduated from Southwest Jiaotong University (SWJTU) with BS degree in 1985 and received his PhD degree in Railway Vehicle Engineering in 1992. He became a full professor in 1994. In 1999, he was appointed Chang Jiang Chair Professor by the Chinese Ministry of Education. Currently, he is a chair Professor of Railway Engineering at SWJTU, the Chairman of Academic Committee of Southwest Jiaotong University, and the Director of Train and Track Research Institute. Professor Zhai is one of the leading scientists in railway engineering in the world. His research activities are mainly in the field of railway system dynamics, focusing on train-track-bridge interactions. He established a new theoretical framework of vehicle-track coupled dynamics so as to be able to investigate the dynamical problems of overall vehicle and track system. He developed a dynamic model and computational software TTBSIM for solving the large-scale train-track-bridge interaction problems and proposed a method to assess the running safety and ride comfort of high-speed trains passing through different types of bridges at the design stage. His models and methods, well-known as Zhai model and Zhai method, have been successfully applied to more than 20 large-scale field engineering projects for the railway network in China, mostly for high-speed railways. Professor Zhai is the Editor-in-Chief of International Journal of Rail Transportation published by Taylor & Francis Group. He also serves as a trustee of International Association for Vehicle System Dynamics, the President of Chengdu Association for Science and Technology, the vice President of the Chinese Society of Theoretical and Applied Mechanics, and the vice President of the Chinese Society for Vibration Engineering.

Southwest Jiaotong University, China

High-speed railway has achieved rapid development in China during very short period, along with many scientific and technological challenges. In this presentation, an overview is given on the development of high-speed railways in China, including the history of raising train speed and current status of high-speed railways. Key challenges focusing on dynamics problems are discussed at design stage and at operation stage of Chinese high-speed railways, respectively. For example, how to employ the vehicle–track coupled dynamics theory to determine the design parameters of plane curves and vertical profiles for different high speed lines without any design standard at the beginning of development of high-speed railways in China? How to use the train–track–bridge dynamic interaction simulation to evaluate and assess the running safety and ride comfort of high-speed trains passing through various types of bridges at the design stage? How to maintain the high ride comfort of high-speed trains running on various infrastructures at operation stage? Some strategies for coping with the challenges are introduced on the basis of speaker's research work on railway system dynamics, and some application examples are provided to demonstrate their effectiveness in practical high-speed railway engineering.



PREMISES FOR EFFECTIVE TEACHING AND LEARNING: STATE OF THE ART, NEW OUTCOMES AND PERSPECTIVES OF CLASSROOM ACOUSTICS

Arianna Astolfi
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Arianna Astolfi, PhD, is an Associate Professor of Building Physics at the Department of Energy of the Politecnico di Torino, Italy, where she is responsible for the Applied Acoustics Group and Laboratory. She is co-chair of the Technical Committee on "Room and Building Acoustics" of the European Acoustical Association, a member of the National Council of the Italian Acoustic Association, and a member of the UK Institute of Acoustics and of the Acoustical Society of America.

Professor Astolfi regularly organizes Structured Sessions on Room Acoustics for EAA Conferences and she is frequently appointed as Chair-person of "Classroom Acoustics" sessions. She serves the UNI committee, which is developing technical standards on acoustic requirements for such indoor environments as schools, offices and hospitals. She is a member of the editorial board of the "Acoustics" and "Building Acoustics" journals, guest editor of a number of special issues in international journals and author of more than 50 peer-reviewed articles on such topics as classroom acoustics, voice monitoring, concert-hall acoustics, soundscape and sound insulation.

She has registered two patents and has created two start-ups, that worked in the I3P incubator of the Politecnico di Torino. She has participated in the scientific committees of several conferences in the field of acoustics and building physics and has been invited, as an expert speaker, to conferences in the fields of Audiology, Phoniatrics, and Speech Therapy.

Politecnico di Torino, TEBE Group, Department of Energy, Corso Duca degli Abruzzi 24, 10129, Turin, Italy

Many booklets and standards have already been published on classroom acoustics in several Countries, based on studies that were carried out up to ten years ago and which were mainly focused on the speech intelligibility of pupils under noisy conditions. In the last decade several studies have started to consider the complex speech communication scenario in classrooms, where acoustic requirements are needed for both teachers and pupils. The voice monitoring of teachers has revealed challenging conditions for speaking as a result of bad acoustics, with consequences on vocal health. Research has underlined the importance of voice support from the room, which has led us to reconsider the optimal reverberation time in classrooms, whose tendency is towards higher values than those for listening. On the other hand, it has been proved that a high reverberation increases the listening effort and decreases reading abilities. Thus, the question of the optimal reverberation time for speaking and listening arises, as well as the need to optimize the design of classrooms to support voice and control the sound tail. The perceived reverberation is closely related to the perceived acoustic quality, which is recognized as the most important environmental aspect in classrooms. Reverberation also amplifies the noise produced by pupils themselves and affects their well-being. To cope with this, a new device has been introduced to inform pupils on the need to lower their voices and respect others.
A summary of the state of the art of classroom acoustics is given in this lecture, together with the new findings on the effects of bad acoustics on pupils' learning and well-being and on teachers' vocal behavior. A new paradigm on speech communication is needed in classrooms that should involve both teaching and learning. Further work is required to investigate the factors that underpin this complex communication scenario.



MANAGING UNCERTAINTY IN BUILDINGS ACOUSTICS MEASUREMENTS AND PREDICTIONS

Christian Simmons
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Christian Simmons has worked as a researcher and consultant in acoustics since 1986, mainly within the field of building acoustics. He presented his Ph.D. thesis in 2009, based on ten years of practical experiences with the EN 12354 series of standards for the estimation of performance of buildings, especially the uncertainty aspects and the requirements on products to make them safe as input data to such calculations. He is also an adviser to several national authorities in Sweden as well as a member of ISO and CEN working groups on acoustics.

Simmons akustik & utveckling ab

In 1996, new requirements on low frequency sounds 31-200 Hz from service equipment's in buildings called for a new measurement procedure with reasonable reproducibility in the field, i.e. with efficient averaging of spatial and time domain variations. After a systematic comparison of various national and international methods, the "selected corner method" was adopted. After a round robin, this procedure was introduced in the EN ISO 16032 and EN ISO 10052 standards. About 10 years later, a similar concept was introduced in the sound insulation methods in EN ISO 16283 which I had tested in a few ordinary rooms. The reproducibility of standardized sound insulation measurements in the field had also been tested in a round robin. The results were contributed to ISO to specify typical standard deviations of airborne and impact sound insulation measurements in the ISO 12999-1. For the project design phase, theoretical predictions of the performance of buildings were standardized in the EN 12354 series in 2000, based on the performance of floors, walls, windows etcetera. An extensive comparison of sound insulation of concrete slabs in situ resulted in a recommended safety margin of 3 dB between an estimate and a requirement, where about 9 field measurements out of 10 should fulfil this requirement. Then CLT elements were introduced as separating elements, to challenge the application of EN 12354 and call for new uncertainty studies. Initial comparisons indicated an unsatisfactory uncertainty. Some steps towards a more stable prediction routine will be discussed, but much work remain. Residents in 38 newly built timber or concrete framed houses in the frequency range 20-5000 Hz have rated "thump sounds" from walking neighbors'. The correlation between their perceived annoyance and various weighted single numbers for the measured impact sound levels could be improved considerably by extending the frequency range to 25 Hz in the case of light weight floors (say < 200 kg/m2).



DESIGN OF AIR-CONDITIONING SYSTEMS FOR NOISE AND VIBRATION CONTROL

Malcolm J. Crocker
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Malcolm Crocker obtained his bachelors degree in Aeronautical Engineering, and master's degree in Noise and Vibration Studies both from Southampton University. He obtained his PhD in Acoustics from Liverpool University. He worked first at Supermarine Aircraft and Vickers Armstrong Aircraft in the United Kingdom and then for Wyle Labs, Huntsville, USA on the Lunar Saturn V launch noise. He has held full professor positions at Purdue, Sydney and Auburn Universities. He was named Assistant Director/Acoustics of the Ray W. Herrick Laboratories, Purdue University in 1977, where he conducted research on vehicle and machinery noise from 1969 to 1983. At Auburn University he served as ME Dept Head from 1983-1990 and Distinguished University Professor from 1990-2010, where he continues his research in acoustics, noise and vibration. He has published over 300 papers in refereed journals and conference proceedings. In the last 50 years. Dr. Crocker has been principal investigator on over 70 research contracts for industry and government and has supervised over 50 graduate students. He has written nine books including the four-volume, 200-page Encyclopedia of Acoustics, 1997; Handbook of Acoustics, 1998; Handbook of Noise and Vibration Control, 2007; and Engineering Acoustics — Noise and Vibration Control, 2021 for John Wiley & Sons. The Encyclopedia won the 1997 award of the American Association of Publishers for excellence in professional and scholarly publishing in Physics. Crocker served as one of the founding directors of INCE/USA, 1971, one of the four founding directors of I-INCE in 1974, and one of the four founding directors of the International Institute of Acoustics and Vibration (IIAV) in 1995. He was general chair of INTER-NOISE 72 in 1972 and the President of INCE/USA in 1981. Crocker served as Editor-in-Chief of the Noise Control Engineering Journal 1973-1994 and the International Journal of Acoustics and Vibration (IJAV) 1996-2016. He has served as Executive Director of IIAV since 1995. He has numerous awards including three honorary doctorates in Russia and Romania, and fellow and/or distinguished fellow of ASA, IIAV and ASME. He received the 2017 ASME Per Bruel Gold Medal for contributions to noise control and acoustics.

Distinguished University Professor Emeritus - Auburn University (Auburn, Alabama, USA)

There is widespread use of heating ventilation and air-conditioning (HVAC) systems in a variety of small and large buildings. The main consideration facing the designer of such systems is to ensure that the plant provides the required amount of heated or cooled air throughout the building and does not create objectionable noise or vibration either in the areas served by the system or in adjacent areas. Because air must be supplied (and in many cases extracted) by a fan of some kind (axial, centrifugal, or mixed-flow), it is inevitable that some noise and vibration are generated. It is becoming common practice to use systems with very high airflow velocities, which introduce additional problems due to noise generated by the turbulent airflow that is created. However, despite the many difficulties that may be encountered, the noise produced by the system can be controlled if the system is correctly sized and care is taken to ensure that all elements of the system are properly installed. Air-conditioning also makes it possible to use sealed windows, thus giving good sound isolation from most of the outdoor noise. This can be important with buildings situated close to airports, railroads, and highways. Once a completed HVAC system has been installed in a building, it is often very difficult and expensive to correct noise and vibration problems. Thus, great care should be taken at the design stage of a system to select all of the equipment items carefully and to minimize all possible sources of noise and vibration. A successful design can be obtained only by careful cooperation between the architect, ventilation engineer, and acoustical consultant. The primary considerations in selecting the mechanical equipment necessary for cooling, heating, and ventilating a building are related to (i) satisfying its intended use, and (ii) providing acceptable sound and vibration conditions in occupied spaces in the building. In critical cases such as conference rooms, auditoria, bedrooms in homes and hotels and lightweight buildings, the sound and vibration produced by the equipment must be minimized. In order to meet these mechanical and acoustical requirements, it is important to use the source-path-receiver concept.


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