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Presentation av Master's thesis på Chalmers
Boka in i min kalender
Datum3 september 2014
Tid09:00 - 15:00
PlatsTeknisk akustik, Teaching lab
Dear colleagues, staff and students,

You are all most welcome to Master's Thesis presentations Wednesday September 3 in the Teaching lab. at the Division of Applied Acoustics, Chalmers, Sven Hultins gata 8A.

09:00 Daniel Norgren "On the development of an statistical energy analysis model for solid structures."
10:00 Niklas Rosholm "Measurement system for reciprocal calibration"

13:00 Fredrik Norell "Designing and Evaluating Filters for the Concept of Sound Zones"
14:00 Viktor Finell "Modal active control applied to string instruments"

You find the abstracts below.

Kind regards
Patrik Andersson

Patrik Andersson, Associate Professor
Head of the Civil Engineering Program

Division of Applied Acoustics
Chalmers University of Technology
SE – 412 96 Göteborg SWEDEN
Phone: +46 31 772 22 02
Fax: +46 31 772 22 12

09:00 Daniel Norgren "On the development of an statistical energy analysis model for solid structures."
The estimation of velocities and sound pressure levels, using the method of SEA, has been a long going technical issue. Previously, this technique has been used mostly in plates, having a 2D structure, and acoustic cavities, having a 3D structure. Our issue is to expand this theory for usage in modelling solid acoustic cavities such as a e.g. rock block or any other materials. This further complicates the problem of SEA, introducing new boundary conditions, and the type of waves known as the rayleigh wave. The model finally used in the SEA-analysis were chosen to be a cylinder of nylon (PA6GTECAST), because of the convenient size and properties of this object. This thesis is done in co-operation with Atlas Copco Rock Drills AB in Örebro.

10:00 Niklas Rosholm "Measurement system for reciprocal calibration"
This master thesis is a collaboration between SP (Technical Research Institute of Sweden) and Chalmers University of Technology. The project consisted of developing a reciprocity calibration system for ½-inch and 1-inch laboratory standard microphones. Calibration by reciprocity is one of the most accurate techniques to calibrate primary standard condenser microphones. The work included implementing code from a previous system into LabVIEW as well as updating the theory according to new standards and setting up new hardware for the calibration system. An ongoing international key comparison for calibration of 1-inch laboratory standard microphones will determine the precision of the system.

13:00 Fredrik Norell "Designing and Evaluating Filters for the Concept of Sound Zones"
In automotive industry, the strive to optimize the information flow directed towards the driver contributes to an increase in the use of information bear- ing sounds. In order to minimize distractions and maintain high comfort, there is need for a way to direct in-car audio to the intended receiver. This thesis is part of a research project aiming to investigate the use of loud- speaker arrays mounted in the ceiling of vehicles to create sound zones. The focus of the thesis is to accurately compute impulse responses (time do- main), given a set of optimal complex source strengths (frequency domain) and to use the impulse responses for auralisations and objective analyses. Three frequency domain methods are evaluated: the mirroring method and two variations of homomorphic filtering. The mirroring method achieves separation between the driver seat and the passenger and back seats in the order of 17 dB and 24 dB respectively, with a variation of around 1 dB de- pending on which source sound is used. The delay time introduced by this method is 40 ms, i.e. small enough to be neglectable even for two-way com- munication. The homomorphic filtering methods achieve 7 − 13 dB worse separation, but in return have smaller initial delay in the impulse response. The results of the thesis indicate that the current strategy for sound zones is feasible, although many challenges remain. One of these is to increase the frequency range to improve e.g. speech intelligibility.

14:00 Viktor Finell "Modal active control applied to string instruments"
This master thesis has been done in collaboration with the IRCAM (Institute for Research and Coordination of Acoustics and Music), the IJLRDA (Jean le Rond D'Alembert's Institute), Chalmers University of Technology and the ENS (Ecole Normale Supérieure) de Cachan. In this study, modal active control will be applied to musical instruments: a simplified string instrument, a guitar and finally a simplified wind instruments. It will be showed that the control of damping and/or frequency of the modes of the instruments can be done, leading to local modifications of their vibrations of decades of dB's. Moreover, a synthesis of guitar pluck will be done and used for a comparison study with experimental results.
Uppdaterat 2014-08-26
Utskriftsvänlig sida
Svenska Akustiska Sällskapet, 0705 948142, hans.jonasson@sp.se, PG 320856-8
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