On Friday 19th August Gerd Høy Marbjerg successfully defended her PhD project: Room acoustic simulation tool for the optimization of absorbing ceilings.
The aim of the project was to develop an advanced simulation tool which employs impedance descriptions of the surfaces making it sutable for optimzation of absorbing ceilings.
"The examiners were in agreement that the thesis addresses a very difficult problem and presents highly original work."
If a simulation tool is to be used for the optimization of absorbing ceilings, it is important that it includes a good acoustical description of the surfaces. In most available tools the surfaces are described by how large a portion of the incident energy is absorbed and how large portions of the reflected energy are specularly and diffusely reflected. These properties are determined by assuming that the angle of incidence of the sound on the absorber is random.
Rooms where absorbing ceilings are installed are often small rectangular rooms with most of the absorption located on the ceiling. In such rooms the angle dependence of the absorption and phase shifts on reflections play an important role. To be able to model both specular and diffuse reflections a combination of the image source model and radiosity will be used in the project.
The examiners were in agreement that the thesis addresses a very difficult problem and presents highly original work. In principle, it combines methods that operate in different domains that have been previously treated as incompatible. This work provides an important new tool that is amongst the first to simulate room acoustics in the medium frequency range. Further, it identifies important deficiencis both in using only energy-based numerical models and in the current practice of characterizing material properties. As such, we anticipate this will impact both further theoretical research and future practical applications including measurement techniques.
The project was an industrial PhD, funded by Saint-Gobain Ecophon.
Principal supervisor: Associate professor Jonas Brunskog, DTU Elektro
Co-supervisor: Associate professor Cheol-Ho Jeong, DTU Elektro
Examiners: Associate professor Ewen MacDonald, DTU Elektro, Professor Lauri Saviolj, Aalto University, Finland, Research Director: Alain Le Bot, École Centrale de Lyon, France,
Chairperson: Associate professor Vicente Cutanda Henriquez