You may remember huge lecture halls with 200 students from university. When a lecture wasn’t interesting, you could simply close your eyes or chat quietly with your neighbor. When you were interested in the subject, however, you wanted to be able to follow the lecture without being disturbed. Imagine a lecture halls like this echoing so much the person who speaks can hardly be understood! This was the case at the University of Twente, where we were asked to improve the acoustics.
Before we take a look inside the University of Twente, we would like to explain to you what reverberation is and what causes it. When sound repeatedly bounces against walls and objects in a complicated pattern, reverberation occurs. The size of the room and the material of the walls play an important role in this phenomenon: The larger the space, the more reverberation occurs. Building materials play an additional role: wood, for example, absorbs noise much better than concrete does.
So, what exactly is "good reverberation"? To ensure good speech intelligibility in large rooms, such as lecture rooms, theroom’s reverberation time should not exceed 1 second. The reverberation time represents the amount of time during which sound can still be heard once someone stops talking.
We improved the acoustics in several of the university’s rooms: in the lecture halls, for example, we improved speech intelligibility for lectures in front of a group as well as group discussions.
In order to improve the acoustics of the two lecture halls of the “De Spiegel“ building, we installed several sound-absorbing products, such as ARTpanels and ARTwalls. As a result, the reverberation time was reduced to 1.09 seconds in lecture hall 1 and to 1 second in lecture hall 2 (with this hall absorbing the sound better because its seats are covered with fabric).
The “Bastille” atrium is a multifunctional space for activities such as workshops and events. The disadvantage of this space is its long reverberation time of 2.6 seconds, making it hard to understand the speakers. By placing 124 square meters of acoustic wall covering, we managed to reduce the reverberation time to 1.6 seconds.
Speakers in the large conference room of the university could hardly be understood due to disturbing reverberations. By placing 40 square meters of ARTwall, we reduced the reverberation time to an acceptable level.
Products used: ARTwall (vide) 562 x 290 cm, ARTwall: 1870 x 107 cm and a strip of 1870 x 53 cm mounted against a hollow wall of 18 meters in 2 parts with a 10 cm gap in which a light line is placed. ARTpanels: 7 pieces of approx. 100 x 200 cm with photo print