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Acoustics in the Sound Environment Centre

Within the groups involved in the Sound Environmental Center, acoustic research is going on at the acoustics groups at LTH (in Lund) and at DTU (the Technical University of Denmark, in Lyngby, Demark). The group in at LTH is conducting research in, e.g., building acoustics, and have during the last years reported several interesting projects in this area. I will however concentrate this report on two project related to the group at DTU, as examples.

The first example is the MONICA project, which is a European funded project (www.monica-project.eu/ ) that demonstrates how cities can use IoT technologies to manage sound and security at large, open-air cultural events in the city. Jonas Brunskog is project leader for the acoustic actibvities at DTU within the project – it involves three PhD students, one postdoc and contributions from three associate professors at DTU. The contribution by the DTU group is mainly related to adaptive sound field control of outdoor concerts. Loudspeaker systems for outdoor sound reinforcement typically consist of two loudspeaker line arrays and a set of subwoofers arranged in a horizontal array or as two left-right clusters. In the ASFC, these systems (primary sources) are extended by the use of additional low frequency loudspeakers (secondary sources). These are placed behind the audience in between the primary sources and the neighboring region in which the sound from the event should be reduced (dark zone). The basic idea is to optimize the radiation from the secondary sources in such a way, that the sum of sound pressures from the primary and secondary sources effectively reduces the total sound pressure level in the dark zone. The adaptive aspect of the system is due to the changing weather conditions in outdoor conditions. The system have been developed and tested in a series of large scale tests, including concerts in Tivoli, Copenhagen, and in Turin, Italy. In these tests, we have shown that the system works when the conditions are geometrically simple. We have also faced several practical problem – especially when it come get permission and enough time to do the measurements needed for the system to work. The last experiment took place in Roskilde the 30/11 2019, with a live outdoor concert. Here everything finally went our way, and we got a clear audible reduction of the low frequencies, and a measured reduction of up to 15 dB. The project is now ending, and we are in the face of getting new founding to develop and continue this research.

The second example of a research project related to acoustics is the Forte project ‘Communication, a challenge for the older employee: Need for a communication supporting workplace’ with Viveka Lyberg-Åhlander (LU and Åbo) as PI. This project is in its startup face, and it is a cross-disciplinary research project, including both speech therapy, neural science and acoustics. This project has its origin in the increased retirement age of opera-choristers and in the results from the Stockholm Public Health Survey. The former put focus on the lack of knowledge of aging voice and the latter showed an increased incidence of communication/voice problems after the age of 55 in women and in all after 65. Today, life after retirement is active. However, the knowledge in the area of healthy elderly’s' voice and communication is scarce. Measures taken in the work-environment to support communication are hence, called for. The acoustic part of the project will mainly be investigating the effect of acoustics on vocal loading, cognition, recovery and communication. A research questions is: How will different participants with different inherent characteristics behave in different room acoustic conditions regarding voice use, speech and communication?

Jonas Brunskog, Associate Professor - Department of Electrical Engineering, Technical University of Denmark (DTU)