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Teknisk akustik

Lunds Tekniska Högskola

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Meshes for real-time acoustic rendering

 

Objective
Meshes generated for use in visual rendering are not optimized for acoustical rendering. This project should evaluate existing optimization algorithms and develop a methodology for optimizing these “visual” meshes for use in an acoustical raytracer.

Approach
A model for Vadstena Abbey Church based on 3D scans of its interior has been produced by the Humanities Lab at Lund University. It should be modified and adapted for acoustical purposes, in collaboration with the Humanities Lab and the Division of Acoustics. This Master’s Thesis will evaluate the available methods of optimization and develop an improved model that will be used in the final product.

Application
Real-time visualization has long been a central aspect of for example video games and computer modeling, and with head-tracking technology it is now possible to have quite immersive experiences using a VR headset. However, the acoustic elements have not received as much attention. Sound in computer games are often generated using very simplified models, or with pre-computed samples. While the simplified models may be sufficient for some cases, they set a hard limit on the possible level of immersion. On the other hand, using a method for pre-computing the sound environment is not always possible, for example in cases when the scene can be modified or there are several sound sources moving about, and in the context of computer modeling or design, having accurate and fast responses to changes in the scene is the goal itself.

In order to deal with the shortcomings presented above, an acoustic raytracer has been developed using the NVidia OptiX raytracing engine. This allows for fast and accurate simulation of the sound field, based on the acoustical properties of the surrounding geometry. Raytracing is a common method in graphical rendering, and a lot of optimization techniques already exist. However, these have been evaluated based on the performance for visual applications, and questions remain on the adequacy for the acoustic counterpart.

The Master’s Thesis work is to be completed at the Acoustical Division at LTH. It is part of a larger project in cooperation with universities around Sweden

Student background
The student is expected to have some experience with computer graphics and modeling, as well as algorithms or graphics cards programming.

Notice

If you are interested in this proposal for Master's Thesis work, please contact:

Hanna Autio MSc, Division of Engineering Acoustics, LTH, V-house, 5th Floor, Room: V:5120.

Delphine Bard-Hagberg  Associate Professor, Division of Engineering Acoustics, LTH.

Erling Nilsson, Adjunct Professor, Division of Engineering Acoustics, LTH.


The direction of sound

 

Objective
The human auditory system is adapted to extract a lot of spatial information from a sound field, determining for example the location of a sound source or properties of the surrounding space. Many of the cues used for this information relate to the direction at which the sound waves impinge on the human head and ear. In order to produce accurate and immersive simulations of sound fields in complex environments, this spatial information must be preserved throughout the simulation process.

Approach
A ray-tracer for acoustical simulations has been developed at the Division of Acoustics, LTH. It accurately computes the sound level for a given source and listener configuration, but the spatial information is not currently retained. This Master’s Thesis aims at extracting this data from the simulation.

Application
This project is part of a larger collaboration with researchers from universities around Sweden, which aims at producing a historically accurate and realistic VR simulation of Vadstena Abbey Church. Due to the architecture in the church, the directional aspects of the sound field is especially important and this thesis is a vital part in the project.

The results of this project could be used in a large number of applications, both in the field of immersive computer technology (such as Virtual Reality or computer games) and design.

Student background
The student should feel confident in mathematics and programming. Some experience with CUDA is advantageous.

Notice

If you are interested in this proposal for Master's Thesis work, please contact:

Hanna Autio MSc, Division of Engineering Acoustics, LTH, V-house, 5th Floor, Room: V:5120.

Delphine Bard-Hagberg  Associate Professor, Division of Engineering Acoustics, LTH.

Erling Nilsson, Adjunct Professor, Division of Engineering Acoustics, LTH.


Numerical models for predicting low-frequency noise


Description

Densification of cities due to growing population in towns brought alongside high-rise buildings, nowadays those often being constructed of lightweight, cheaper and sustainable materials such as wood. Due to the latter, existing vibration sources such as motorways, railways, harbours or simply the neighbours’ daily activities can have a very high impact on the vibroacoustic behaviour of such structures, triggering complaints from the people living in them.

The objective of this master thesis is to investigate modelling techniques (using the finite element method) to create vibroacoustic prediction tools of high-rise wooden buildings. The development of the numerical methods will be done by combined use of measurements and simulations. More specifically, focus will be put into the prediction of the sound pressure field radiated into a room as well as the description of typical loads. Moreover, proposing solutions (both from a structural and acoustic point of view) which can improve acoustic comfort in dwellings subjected to different types of loads is in the scope of this project.



Anslag
fileadmin/tekniskakustik/masterprojects/available/TAxs08.pdf

Om du är intresserad av detta förslag på examensarbete, kontakta:

Juan Negreira  Assistant Professor, Avdelningen för teknisk akustik, LTH

Delphine Bard-Hagberg  Associate Professor, Avdelningen för teknisk akustik, LTH


Development of a General Acoustics Model for an Arbitrary Camera Design


Category
: Acoustics/Audio
Scope: 2 students completing 30 credits (20 weeks) each

Education: Acoustics-oriented Civil Engineering, Mechanical Engineering, Electrical Engineering, Engineering Physics, Engineering Mathematics, or similar

Background
Axis is currently investing in the improvement of audio quality in our cameras. We have the competence to achieve satisfactory performance from the electronics and software but could use a bit more experience in the field of acoustics in order to achieve the desired acoustic performance, mainly in terms of frequency response. Having a theoretical, adaptable acoustic model would help us to identify critical aspects of the mechanical design and adjust these accordingly for better audio performance.

Goals
Part One – Research:

  • Find out what parameters needs to be taken into account (e.g. physical dimensions, materials used, etc.).
  • Collect common camera characteristics that need to be modeled (such as camera lens, acoustic leakage in connector ports, multiple microphones, etc.) to make the model usable for as many camera types as possible.
  • Evaluate the best model to use. E.g. make an equivalent electrical circuit for simulations in SPICE, make a purely numerical model using, for example, MATLAB, etc

Part Two - Development of Acoustic Model:

  • Develop the model according to the results from part one.

Part Three - Evaluation:

  • Make measurements on one or several cameras and compare with the model.
  • Use the model to identify the critical acoustic components of a camera, modify the camera and see if the acoustic performance is improved as expected.

 

Who are you?
This thesis work is targeted towards two students with good understanding in acoustics and sound propagation. We hope that you have a strong interest in audio design and enjoy the pursuit for higher quality audio.

OK, I am interested! What do I do now?
You are valuable to us – how nice that you are interested in one of our proposals! There are a few things for you to keep in mind when applying.

Applications are accepted in both Swedish and English, and you apply via the proposal advert.

  • The announced theses are open only to students affiliated with a Swedish university/college either directly or via an exchange program.
  • When the thesis proposal states that it includes two students working together, we would like you to apply in pairs. In these cases, send one application each but make sure to clearly state in your application who your co-applicant is. If you have any questions regarding this, please do not hesitate to contact us.
  • Please attach your CV and University/college grade summary.


We look forward to hearing from you!

Send application

More Information
For more information, contact Johan Sunnanväder or Per Ola Olsson, Axis Communications, on +46 46 272 1800.

 


Noise Mapping of a Magnetic Resonance Imaging (MRI) System


Background

Magnetic Resonance Imaging (MRI) is a technique used in the field of radiology where a strong magnetic field, radio frequency (RF) waves and field gradients are employed to achieve images of the inside of the patients’ body. A known issue when it comes to MRI examinations is the extremely high noise present caused by the gradient magnetic field. Rapid current switching within the coils produces enormous Lorentz forces acting on the coils which, in turn, emits noise. The acoustic noise varies depending on the choice of image parameters and the MRI sequence selection. Other noise sources associated with an MRI system are RF waves and noise produced by sub-systems like fans and cryogen systems used for cooling of the magnet.

The most common way for noise controlling an MRI device is passive noise control, where the patient is asked to wear earplugs and/or headphones. While examinations often last between 20-30 minutes, wearing headphones under such a long period of time in combination with other factors (such as the patient having to remain completely still during that time) may be extremely uncomfortable for the person in question.

Aim
The aim of this project will therefore be to reduce the noise produced by the MRI system as well as the one transmitted into other adjacent rooms. To that end, a pre-study will be first carried out in order to determine the overall noise level of the system and to establish a noise radiation map. To do so, baseline data must be collected and the sound field of the MRI system should then be determined. Challenges such that of measuring surrounded by a strong magnetic field as well as the eventual noise-reduction strategies to be taken, should be addressed.

Mer information!

Om du är intresserad av detta förslag på examensarbete, kontakta:

Juan Negreira  Avdelningen för teknisk akustik, LTH


Predicting Structure-borne Sound


Background
Since noise exposure can disturb the well-being, acoustical comfort in the built environment is of great importance when constructing new dwellings. Population growth causes densification of cities, which together with space limitation issues, lead to buildings being constructed closer to existing vibration sources such as motorways and railways, and vice versa. At the same time, architectural trends, environmental benefits and cost result in increased use of lighter materials such as wood and hollow-core concrete slabs. Light-weight structures make the achievement of acoustical comfort in dwellings an increasing challenge. A major issue when designing buildings regarded as acoustically pleasant, especially in the low-frequency range, is the lack of reliable prediction models to be used during the design stage of the building. Predictions of structure-borne noise are nowadays mostly made based on measurements performed on existing buildings and engineers’ experience. Hence, it is of interest to develop tools (e.g. computer models) that could adequately predict noise and vibrations. The computer models developed for that purpose could combine and couple different numerical methods, e.g. the Finite Element Method and Statistical Energy Analysis, and they may also use measurement data as input.

Aim
The aim of this Master’s Thesis project is to investigate and develop numerical models that could be used in the early design stage of structures (e.g. buildings, tunnels), specially aimed at predicting structure-borne noise in railway tunnels. With such tools, one could address vibration and noise issues as well as undertake mitigation measures before the structure is constructed. The tools will also enable time and cost savings for the building industry in terms of less retrofitting and wiser selection of design solutions.

Mer information!

Om du är intresserad av detta förslag på examensarbete, kontakta:

Juan Negreira  Avdelningen för teknisk akustik, LTH


Development of Finite-Element Models to Predict Impact Sound Insulation


Beskrivning:

Dissatisfaction of dwellers due to impact noise is a common problem often encountered in wooden multi-storey buildings nowadays. Such problems could be lessened by addressing vibroacoustic issues during the design phase of buildings if proper prediction tools were available for the engineer. Unfortunately, product development nowadays is still carried out in the aftermath of the construction based on engineers’ experience and measurements performed on already existent buildings; due to the difficulties involved in predicting vibroacoustic behaviour of such constructions. The substitution of measurements by easy-to-use numerical predictive models, however, must take place only after those have proven to possess enough accuracy for the predictions carried out. Along those lines, proper modelling of the excitation sources, the structural element involved (e.g. floor) as well as accurate modelling of the rooms is needed.

The objective of this master thesis is to investigate and develop improvements for numerical tools (using the finite element method) for purposes of prognosis. More specifically, focus is put into description of the loads involved (e.g. walking loads, the standardised ISO tapping machine used as impact excitation source for evaluating step sound insulation according to the ISO standards, etc.) as well as on the description of the sound pressure field of the receiving room (i.e. absorption, etc).

General simplified guidelines for creating finite element prediction tools are to be proposed. Ultimately, a prediction tool combining the knowledge stemming from the investigations performed will enable the determination of the standardised single number acoustic ratings obtained from measurements. By use of them, acoustic comfort could be address during the design phase of buildings without having to spend that much money and time in performing measurements and building mock-ups.

Mer information!

Om du är intresserad av detta förslag på examensarbete, kontakta:

Juan Negreira  Avdelningen för teknisk akustik, LTH


Ultrasonics


Beskrivning:

This project is part of a PhD program that considers the development of a novel plane-strain biaxial loading device for granular rocks. This apparatus aims at the investigation of strain evolution at different scales and the simultaneous assessment of the evolution of stiffness, in a full-field sense. All these cannot be provided by a single technique and thus a combination of approaches is required. More specifically, the multi-scale strain measurements will be accomplished by combining Neutron Diffraction with Digital Image Correlation (DIC) and the monitoring of the evolution of damage will be realised with the use of Ultrasonic Tomography (U-Tomo).

The objective of the current project is the development of novel ultrasonic transducer arrays for the realization of the U-Tomo. These transducer arrays will have to be flexible in order to be able to follow the deformation of the rock specimens, since the U-Tomo technique is intended to be used in-situ (i.e., while realising deformation experiments on rock samples) and simultaneously with Neutron Diffraction and DIC.

Om du är intresserad av detta förslag på examensarbete, kontakta:

Delphine Bard  Avdelningen för teknisk akustik, LTH


Utformning av bullerplank


Beskrivning:

VERKSAMHET
I Svedala kommun i närheten av Malmö Airport ligger Sveriges sydligaste racingbana. Sturup Raceway upprättades år 1972 och är idag en tekniskt krävande bana för både bilar och motorcyklar. Utöver tränings- och tävlingsanläggning för motorsport så är Sturup Raceway även en plats för konferenser, företagsevent och racingupplevelser för privatpersoner. Det är också ett utbildningscenter, som bland annat erbjuder halkkörning och utbildningar inom bilsäkerhet och Eco Driving.  Läs mer här!

Om du är intresserad av detta förslag på examensarbete, kontakta:

Delphine Bard  Avdelningen för teknisk akustik, LTH eller

Helene Ensegård  Kontaktperson Miljöbron Skåne, Tel.0706 – 35 39 25

 


Åtgärder för att minska buller


Beskrivning:

VERKSAMHET: MOM EVENTS
Ljungbyhed Park, tidigare känt som F5, är numera ett center för konferens och event. Företaget MOM Events driver banan som är belägen på det gamla kortbanesystemet där det förr i tiden lyfte propellerplan. Banan som är utmärkt för testkörning och motorrelaterade evenemang anses vara en av de mer säkra banorna i Sverige då det finns stora avåkningszoner av gräs. Exempel på aktiviteter som MOM Events anordnar är Bli Racingförare för en dag, Safety driving, Sparsam körning, Förarcoaching, Skåne truckshow, bilträffar, rallytävlingar m.m.  Läs mer här!

Om du är intresserad av detta förslag på examensarbete, kontakta:

Delphine Bard  Avdelningen för teknisk akustik, LTH eller

Malin Planander  Kontaktperson Miljöbron Skåne, Tel. 0732 – 75 04 29

 


Development of Smartphone app for reverberation time measurements in rooms with furniture


Beskrivning:

This project is aimed to develop an app in order to encourage users to measure reverberation time in any room that might be in need of acoustic measures. The app should measure impulse response of the room. It should be possible to take pictures that can be uploaded and connected to the actual measurement. It has to evaluate measurements in the octave bands 125-4000 Hz and it should be able to use a manual impulse source. Please, read more here!

Om du är intresserad av detta förslag på examensarbete, kontakta:

Delphine Bard  Avdelningen för teknisk akustik, LTH


Auralization using GPUs


Beskrivning:

Auralization in room acoustics aims at making the acoustics of a room audible. Vorländer defines the term auralization as follows [Vorländer, 2008]: ”Auralization is the technique of creating audible sound files from numerical (simulated, measured, or synthesized) data.”

The idea is to enable a user to experience the sound quality of a room even though that room might not yet exist. Traditionally, the process of creating the convolution corresponding to the auralization of a sound in a single point in a room has been computationally hard. In this project we propose a different approach in solving the problem is proposed. Please, read more here!

Om du är intresserad av detta förslag på examensarbete, kontakta:

Delphine Bard  Avdelningen för teknisk akustik, LTH


Statistical Investigation of Human Walking Pattern

  Statistical Investigation of Human Walking Pattern


Om du är intresserad av detta förslag på examensarbete, kontakta:


Delphine Bard  Avdelningen för teknisk akustik, LTH

Göran Sandberg  Institutionen för byggvetenskaper, LTH


Hedson Technologies

Hedson Technologies söker examensarbetare

Hedson Technologies utvecklar hjultvättar för bland annat däckverkstäder. Vi vill sänka ljudnivån genom ljuddämpning i maskinerna för att förbättra arbetsmiljön för våra kunder. Läs mer här!  

Om du är intresserad av detta förslag på examensarbete, kontakta:

Delphine Bard  Avdelningen för teknisk akustik, LTH

Erling Nilsson  Saint-Gobain Ecophon AB, Tel: 042 179734
                        Mail: erling.nilsson@ecophon.se


Modellering av porösa absorbenter med ytskikt och jämförelser med mätningar i impedanstub


Beskrivning:

Examensarbetet går ut på att utvärdera några befintliga teoretiska och empiriska modeller för porösa material. Modellerna ska användas för att beräkna ytimpedans och absorptions- och reflektionskoefficienter för flerskiktsabsorbenter. Fysikaliska parametrar relevanta för de absorberande egenskaperna ska identifieras och där så är möjligt bestämmas. Flerskiktsabsorbenterna formuleras med överföringsmatriser där delmatrisernas fysikaliska innebörd ska framgå. Modellerna implementeras i ett Matlab-program (Graphical User Interface)) som grafiskt möjliggör en parameterstudie. Verifiering av modellerna görs genom jämförelse med mätningar i impedanstub.

Referenser:

  1. J.F. Allard. Propagation of sound in porous media, modelling sound absorbing materials. Elsevier Science Publishers LTD 1993. Applied Science.
  2. U. Ingard. Notes on Sound Absorption Technology, 1994, Noise Control Foundation.
  3. T. J. Cox and Peter D’Antonio. Acoustic Absorbers and Diffusers, Theory, Design and Application, 2004, Spon Press.
  4. K. V. Horoshenkov. Characterisation of acoustic porous materials. Vol. 28. Pt.1. 2006. Proceedings of the Institute of Acoustics.
  5. X. Olny and R. Panneton. Acoustical determination of the parameters governing thermal dissipation in porous media. J. Ac. Soc. Am., 123:814–824, 2008.
  6. R. Panneton and X. Olny. Acoustical determination of the parameters governing viscous dissipation in porous media. J. Ac. Soc. Am., 119:2027–2040, 2006.

Om du är intresserad av detta förslag på examensarbete, kontakta:

Delphine Bard  Avdelningen för teknisk akustik, LTH

Erling Nilsson  Saint-Gobain Ecophon AB, Tel: 042 179734
                        Mail: erling.nilsson@ecophon.se


”Kalibrering” av rumsakustisk mjukvara


Beskrivning:

”Kalibrering” av rumsakustisk mjukvara (Odeon, CATT, Icare, …) mot fältmätningar. Fältmätningarna utgörs av det klassrumsmätningar som utförts vid Ecophon där mätningar utförts i 19 klassrum för en rad rumsakustiska konfigurationer. Binaural inspelningar av tal genomfördes också. Syftet med arbetet är att få relevant indata till simuleringsprogrammen när det gäller tak- och väggabsorbenternas vinkelberoende egenskaper och att kvantifiera ljuddiffusionen av typisk klassrumsinredning.

Om du är intresserad av detta förslag på examensarbete, kontakta:

Delphine Bard  Avdelningen för teknisk akustik, LTH

Erling Nilsson  Saint-Gobain Ecophon AB, Tel: 042 179734
                        Mail: erling.nilsson@ecophon.se


Room Acoustic Comfort™


Beskrivning:

Vid Ecophon har en metodik för rumsakustisk design utvecklats. Metodiken innebär att Människan – Rummet – Aktiviteten utgör hörnstenar vid planering för rumsakustisk komfort. När det gäller människan beaktas hörselns flerdimensionella karaktär vilket innebär att flera rumsakustiska mått används vid rumsakustisk utvärdering. Mått som används är efterklangstid, Clarity C50, Strength (se ISO 3382) och ljudutbredningsmått som DL2 och DLf (se ISO14257). Måtten svarar mot de mänskliga upplevelserna av efterklang, taltydlighet, hörstyrka och rumslig utbredning. Beroende på den aktivitet som pågår i rummet kommer vissa av dessa parametrar att bli mer betydelsefulla än andra för den rumsakustiska designen. Vidare, beroende på rumstypen kommer parametrarna att vara mer eller mindre oberoende. Uppgiften i examansarbetet är att fastställa dessa RAC-parametrar för några olika rumstyper som t.ex. kontor med öppen planlösning, klassrum, matsal, förskola.

Om du är intresserad av detta förslag på examensarbete, kontakta:

Delphine Bard  Avdelningen för teknisk akustik, LTH

Erling Nilsson  Saint-Gobain Ecophon AB, Tel: 042 179734
                        Mail: erling.nilsson@ecophon.se


Kvantifiering av ljudskattering


Beskrivning:

Uppgiften är att ta fram en förenklad mätmetod för att bestämma skatteringkoefficienten enligt ISO 17497-1:2004.

Om du är intresserad av detta förslag på examensarbete, kontakta:

Delphine Bard  Avdelningen för teknisk akustik, LTH

Erling Nilsson  Saint-Gobain Ecophon AB, Tel: 042 179734
                        Mail: erling.nilsson@ecophon.se


Sidansvarig: Bo Zadig