At the beginning of the Student Acoustics Seminar, which took place on January 22, 2026, the participants were welcomed by the chairman of the Czech Acoustics Society, Prof. Ondřej Jiříček. "I am very pleased that this event is becoming a tradition. I hope that its level will continue to rise. Therefore, I wish all the speakers every success. At the same time, I hope that they will become a breeding ground for new acousticians who will gradually join the Czech Acoustical Society and do credit to this field," said Prof. Jiříček.
Students from four universities spoke at the conference: in addition to CTU, these were Palacký University in Olomouc, Brno University of Technology, and the University of West Bohemia in Pilsen.
Acoustic modifications in heritage-protected halls
Old churches and larger cathedrals have one characteristic in common, which is a very long reverberation time, often exceeding eight seconds. This is traditionally suitable for organ music or religious chants. Thanks to their ability to create a magical atmosphere, they are often sought-after locations for various cultural and social events. For example, for electronic music concerts or community events with a speaker who needs to be understood. However, this requires a shorter reverberation time. Jan Filip Müller, a student in the Electronics and Communications bachelor's program, focused on this problem in his contribution.
"The fact that these are listed buildings complicates matters greatly. It is not possible to make structural changes to them or alter their character. For example, we cannot install acoustic panels. It is necessary to use non-invasive solutions. This could be, for example, the use of helium-filled balloons as acoustic absorbers, which would be released into the space before the event," described Jan Filip Müller. In addition, the reverberation time can be regulated according to their quantity. "We need a different reverberation time for each event. The number will be different for a concert than for an event with a speaker," he added.
Müller conducted his research during his stay at the University of Le Mans, using the intermittent noise method. He divided the research into four phases. First, he measured the reverberation time of an empty reverberation chamber, then with balloons filled with air, and in the next phase, he performed measurements with balloons filled with helium. The fourth phase, which the student will carry out in the coming semester, is simulation. He will perform this in the COMSOL program, testing a larger number of balloons and also testing their different dimensions.
"Helium has absorbent properties compared to air. With 15 balloons, the difference is already one second," said Müller.
Yerba maté as an alternative insulation material
During the Student Acoustics Seminar, not only bachelor's and master's students, but also doctoral students are traditionally given the opportunity to present their work. One of them was Jorge Joaquin Garcia, who is studying for his doctorate at both the Faculty of Electrical Engineering of the Czech Technical University in Prague and the Università degli Studi di Brescia in Italy.
In his presentation, he explored the potential of biological waste as a source for the development of sustainable acoustic materials. Specifically, he focused on the use of leached yerba maté leaves. This is a traditional South American drink with stimulating effects (due to its caffeine content), which is prepared from dried and crushed leaves of the Paraguayan holly. Although this drink is still most widely consumed in South American countries, its popularity in Europe is growing.
The first step was to mix the leached residues from the yerba mate drink with water and starch. After drying, the mass becomes a solid biopolymer. Jorge Joaquin Garcia tested how different grain sizes and densities affect sound absorption.
"The finer the granulometry, the lower the peak amplitudes and the shift to lower frequencies," said Jorge Joaquin Garcia, sharing the results of his research. In other words, the finer the grains, the better the material will absorb sound.
Keeping pace with research in the field of acoustics
For students, participating in the Student Acoustics Seminar is a valuable experience in practicing public speaking and responding quickly to questions from the audience. The seminar brings together not only teachers, but also peers of the same age, who can draw inspiration for their projects and final theses. The audience traditionally includes members of the Czech Acoustical Society, which co-organizes the Student Acoustics Seminar, as well as experts from the field. This gives students the opportunity to meet representatives of companies and establish important contacts in the field.
Students at the Faculty of Electrical Engineering of the Czech Technical University in Prague can study acoustics at the Department of Radio Electronics or the Department of Physics, for example. "Each workplace looks at acoustics from a different angle and focuses on different issues. Thanks to the Student Acoustics Seminar, we can learn about the research our colleagues are working on in the field," says Dr. Petr Honzík from the Department of Radio Electronics at the Faculty of Electrical Engineering of the Czech Technical University in Prague, which co-organizes the Student Acoustics Seminar.
You can watch a recording of the 2026 Student Acoustics Seminar. You can read about what the SAS looked like in 2025 and 2024 on the FEL CTU website.
Photos by Petr Neugebauer, FEE CTU.
