Examensarbeten för masterexamen // Master Theses
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- PostA combination of a road restraint system and a noise reducing device(2017) Burgos, Claudia; Wåssén, Linnéa; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik; Chalmers University of Technology / Department of Architecture and Civil EngineeringBased on measurements performed on a low-height noise barrier, an investigation was commenced on where such product could be implemented with respect to both noise reduction and to road restraint requirements, including traffic safety. By using three noise prediction tools, SoundPLAN (version 7.4), a Boundary Element Method (BEM) and an analytic solution, the screen insertion losses could be estimated and compared. The screen heights that were studied were 1.2m and 1.4m. The noise reducing effects of these screens were investigated in two real cases that were given by Malmö Stad and in a theoretical case. Standards for both a road restraint system and a noise reducing devise have been studied and summarised to facilitate the development of the combined system. The insertion losses for the two heights were 10 dB(A) and 11 dB(A) respectively when calculating for the theoretical situation. For the real case scenarios, the insertion losses were deteriorated to around 3 dB(A), concluded to be due to reflections in surrounding facades. The deviations in insertion loss between the different calculation methods was at most 2 dB but the results for the increased barrier height showed that a higher insertion loss could be achieved. The use of the BEM results, which were pre-calculated and provided to the project, showed that an absorbing screen should be considered when it comes to a lowheight noise barrier, since an even higher reduction could be achieved. A low-height noise barrier should be considered and further investigated since it actually reduces the levels of community noise and has good potential to protect pedestrians from collisions within an urban environment.
- PostA critical review of bending wave loudspeaker technology and implementation(2010) Li, Kuonan; Chalmers tekniska högskola / Institutionen för bygg- och miljöteknik, Teknisk akustik; Chalmers University of Technology / Department of Civil and Environmental Engineering, Applied Acoustics
- PostA dynamic response study on optimal piling depth with respect to ground vibrations(2014) Olsson, Erik; Chalmers tekniska högskola / Institutionen för bygg- och miljöteknik, Teknisk akustik; Chalmers University of Technology / Department of Civil and Environmental Engineering, Applied Acoustics
- PostA FEM model for simulating reflection of sound by a car compartment's windscreen and lateral front windows(2013) Guevara Flores, Edmundo; Chalmers tekniska högskola / Institutionen för bygg- och miljöteknik, Teknisk akustik; Chalmers University of Technology / Department of Civil and Environmental Engineering, Applied Acoustics
- PostA speech intelligibiliy testing system for evaluation of communication- and hearing protection devices(2011) Vidarsson, Ragnar; Chalmers tekniska högskola / Institutionen för bygg- och miljöteknik, Teknisk akustik; Chalmers University of Technology / Department of Civil and Environmental Engineering, Applied Acoustics
- PostA study of sound reflection patterns in studio and control rooms.(2014) Roth, Tina; Chalmers tekniska högskola / Institutionen för bygg- och miljöteknik, Teknisk akustik; Chalmers University of Technology / Department of Civil and Environmental Engineering, Applied Acoustics
- PostAcoustic simulation of power unit encapsulation for construction and mining applications(2012) Golota, Anton; Chalmers tekniska högskola / Institutionen för bygg- och miljöteknik, Teknisk akustik; Chalmers University of Technology / Department of Civil and Environmental Engineering, Applied Acoustics
- PostActive control of first order wall reflections in large cylindrical rooms(2015) Jönebratt, Veronika; Chalmers tekniska högskola / Institutionen för bygg- och miljöteknik, Teknisk akustik; Chalmers University of Technology / Department of Civil and Environmental Engineering, Applied Acoustics
- PostActive Control of Impact Noise, A study on the reduction of the radiated sound power resulting from an impact between a sphere and a plate(2016) Passanesi, André; Chalmers tekniska högskola / Institutionen för bygg- och miljöteknik, Teknisk akustik; Chalmers University of Technology / Department of Civil and Environmental Engineering, Applied AcousticsImpacts are an important noise source of today’s society. From a control standpoint, solutions to problems related to impacts are commonly based on passive methods. In this paper, an active method to control the radiated sound from a sphere impacting a simply supported plate attached to an infinite ba˜e is proposed. The contact force between sphere and plate is modeled by Hertzian contact, this force is then convoluted with the plate’s impulse response. From this, the radiated sound field is calculated by the Rayleigh integral in the time domain. In a following step, an active force is used to act on the plate with the purpose of minimizing the radiated sound power. This control force is estimated using a method based on the LMS algorithm formulated in the time-domain. For di˙erent positions of the impact between the sphere and the plate, the position of the active force is varied and for each case, the LMS algorithm obtains the optimal time record of the force. For non-trivial cases, where the acting force is not in the same position as the impact, results present reductions of up to 13 dB in the simulations of the radiated sound power.
- PostAir-gun signal post-processing and sound transmission modelling in shallow water(2011) Trimoreau, Benjamin; Chalmers tekniska högskola / Institutionen för bygg- och miljöteknik, Teknisk akustik; Chalmers University of Technology / Department of Civil and Environmental Engineering, Applied Acoustics
- PostAn interactive auralization method. Auralization using ambisonics & real-time sound sources(2013) Lindebrink, Josefin; Chalmers tekniska högskola / Institutionen för bygg- och miljöteknik, Teknisk akustik; Chalmers University of Technology / Department of Civil and Environmental Engineering, Applied Acoustics
- PostAnalysis and Estimation of Residential Vibration Exposure from Railway Traffic in Sweden(2016) Arnesson, Matilda; Chalmers tekniska högskola / Institutionen för bygg- och miljöteknik, Teknisk akustik; Chalmers University of Technology / Department of Civil and Environmental Engineering, Applied AcousticsGround-borne vibrations generated by train pass-byes a˙ect the people living close to railways in Sweden. Not since year 1990 there has been estimates made of the amount of people that are exposed to certain vibration velocities from railway traf-fic in Sweden. Furthermore there has never been any transfer factors published for the transmission of vibrations between the ground and the foundation of buildings in Sweden. By measuring ground-borne vibrations in the ground while doing mea-surements in the foundation, data for 51 buildings have been collected from which comparison of transfer factors between ground and foundation have been possible. The data have been analysed as an overall, as well as according to building size and foundation type. The transfer factor between ground and foundation of a building was found to be 0.83 as an overall mean. The majority of the transmission factors are in the range 0.7-1.1 and the transmission factor does not seem to be depen-dent on if the foundation type is suspended foundation or basement. Multi-dwelling buildings seems to have much lower transfer factor than one-dwelling buildings, but more data for Multi-dwelling buildings is needed to establish if this is statistically correct. In order to estimate the amount of people that are exposed to certain vibration velocities from railway traÿc in Sweden, almost 3 000 measurements of vibrations have been classified according to geology at the receiving building. A simple model have been made based on the attenuation of vibrations with distance and on the geology-classified data. Based on geological maps and a database of all properties close to railways, the total number of exposed individuals in Sweden could be estimated. The amount of people where the rms-weighted comfort values are exceeding the vibration levels 0.4, 0.7, 1.0 and 1.4 mm/s were estimated to 54 100, 25 000, 14 200 and 7 300 people respectively. The model for estimation of exposed people could be improved by using more precise soil class information and by including the soil class under the railway in the model. The model could be used to simplify analyses of vibration exposed buildings and to make rough estimates of what vibration level that might a˙ect a building.
- PostApplication of CAE techniques in solving tweeter installation issues(2018) Haddad, Ralph; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik; Chalmers University of Technology / Department of Architecture and Civil EngineeringNowadays the automotive industry is faced with new features that customers demand, which were not a priority a few years ago. Audio performance is one of them and it is quite challenging. To be able to detect, before any physical prototyping if the speaker mounting or installation is acceptable will allow the teams to perform faster design iterations to achieve better audio performance. This paper tackles how different installation details of a tweeter will affect its directivity radiation. Installation details within the automotive industry are usually interfaces, grilles or nearby reflecting surfaces. The investigation is made through numerical modeling, specifically Finite Element Method in this thesis and it is then validated with experimental measurements. As this study is done at high frequencies, some of the issues faced during modeling and measurement will also be discussed.
- PostApplication of cross-talk cancellation to the improvement of binaural directional properties for individuals using bone anchored hearing aids (BAHA)(2010) Liao, Chiao-Ling; Chalmers tekniska högskola / Institutionen för bygg- och miljöteknik; Chalmers University of Technology / Department of Civil and Environmental Engineering
- PostApplying the reciprocal Transfer Path Analysis (TPA) for the airborne sound of power train components(2011) Rissler, Kai; Chalmers tekniska högskola / Institutionen för bygg- och miljöteknik, Teknisk akustik; Chalmers University of Technology / Department of Civil and Environmental Engineering, Applied Acoustics
- PostAssembly of a tire and a vehicle model to predict vibrations at the bushings(2018) Westers, Michael; Johan, Rosholm; Chalmers tekniska högskola / Institutionen för arkitektur och samhällsbyggnadsteknik; Chalmers University of Technology / Department of Architecture and Civil EngineeringThis Master’s thesis targets the prediction of vibrations at the bushings of vehicle rear chassis due to an excitation at the tire patch for early analysis in the devel-opment stage at the Volvo Car Group. In the past a hybrid model has been used, which included a FEM model of a new vehicle design proposal and through mea-surements obtained spindle forces of an existing tire vehicle combination. However it is reasonable that these forces are di˙erent for a new tire vehicle coupling. In this thesis the measurement data is replaced by a modal tire model, which is provided by Continental AG, to become independent of testing existing vehicles. Recep-tance Coupling is used to assemble one tire to the vehicle in the frequency domain. Thereby the vibration levels at a chosen bushing are obtained due to an excitation at the tire patch for seven di˙erent harmonic excitation cases. In addition, a great focus is set on the sensitivity of the coupled solution to modal truncation errors in the tire model. Therefore an error metric is developed, which assesses the similar-ity between two FRFs using a floating bandwidth. As a result a minimum number of modes required for a desired frequency range and excitation case is given. In a second investigation uniform distributed random noise between ± 10 percent is added to the transfer functions of the tire and the vehicle model. The results show a deviation up to around 5 dB above the non-polluted case, for the major part of the frequency range, for some frequencies the coupled result show a greater sensitivity with deviation up to 20 dB for certain noise matrices.
- PostAssessing vibrational behavior of uncertain dynamic systems(2010) Lindberg, Anders; Chalmers tekniska högskola / Institutionen för bygg- och miljöteknik, Teknisk akustik; Chalmers University of Technology / Department of Civil and Environmental Engineering, Applied Acoustics
- PostAssessment and improvement of the acoustical properties of a testing room for bone anchored hearing aids(2015) Loria Gamboa, Mónica; Chalmers tekniska högskola / Institutionen för bygg- och miljöteknik, Teknisk akustik; Chalmers University of Technology / Department of Civil and Environmental Engineering, Applied Acoustics
- PostAssessment of nonlinearities in loudspeakers(2010) Gunnarsson, Viktor; Chalmers tekniska högskola / Institutionen för bygg- och miljöteknik; Chalmers University of Technology / Department of Civil and Environmental Engineering
- PostAuditory source width perception in cochlear implantees and normal hearing individuals(2014) Sharma, Snandan; Chalmers tekniska högskola / Institutionen för bygg- och miljöteknik, Teknisk akustik; Chalmers University of Technology / Department of Civil and Environmental Engineering, Applied Acoustics