Ana Petelj worked as a scholarship holder at the Fraunhofer Institute for Building Physics in Germany from 2013 to 2014. Her project focused on the influence of granule size and thickness on the acoustic characteristics of loose granular absorbers. She independently conducted acoustic measurements and evaluated the data, obtaining new results that improved understanding of granular absorber acoustics. Ana integrated well into the work group and completed tasks diligently. Her work was outstanding and she is thanked for her cooperation, though she has now left the Institute after completing her scholarship.

1. To whom it may concern
Ana Petelj worked in 2013 and 2014 as a scholarship holder of the Deutschen Bundesstiftung Umwelt
(DBU) in the Department of Acoustics at the Fraunhofer Institute for Building Physics in Germany. Her
project was titled »Influence of granule size and thickness of material on the acoustic characteristics of
loose granular absorber«. She was involved in the current research and project work of the working
groups Noise Control and Room Acoustics and covered the topic in the context of and according to the
requirements of our research area absorber development.
Ana has devoted to her subject with great commitment and in the shortest time she got familiar with the
work equipment, measurement techniques and software programs existing at the Institute. She
independently carried out the acoustic measurements and evaluated measurement data with regard to
the model calculations created by herself. In the framework of the project new and valuable results were
obtained that contributed to the understanding of the acoustics of loose granular absorbers. With this
scholarship, Ana reached her goal to model theoretically uniform loose granulates, to determine the
material parameters and to establish an excellent agreement between measured and computed
absorption data.
Ana has integrated perfectly into the work group, also her personal behavior was always impeccable and
collegial. She solved the tasks entrusted to her with diligence, initiative and commitment always to our
complete satisfaction.
Ana left us after the end of the scholarship. We deeply regret this, because she has done outstanding
scientific work. We thank her for her cooperation and wish her all the best for her future life.
Dr. Peter Brandstätt
Group Manager Noise Control and Vehicle Acoustics
Department Acoustics
Fraunhofer Institute for Building Physics IBP
Nobelstr. 12 | 70569 Stuttgart | Germany
Phone: +49 711 970-3392
peter.brandstaett@ibp.fraunhofer.de