The organizers are pleased to welcome you to the 23rd International Congress on Acoustics in the beautiful and historical city of Aachen. The congress integrates the 4th EUROREGIO 2019, the regional conference of the European Acoustics Association. The technical program includes plenary, invited, contributed, and poster papers covering all aspects of acoustics in a very wide interdisciplinary range. In addition, there will be several special events focusing on Early Career Acousticians, on Acoustics in Industry, and on Public Outreach. Many activities are already in the context of preparation of the International Year of Sound 2020, organized by the International Commission for Acoustics.

As the congress chairs, we like to thank all the authors, session and topic organizers for their contributions to the event. Special thanks go to the Technical Chair, Martin Ochmann, and his team for acquiring 147 structured sessions and for arranging further 14 general sessions. Our sincere appreciation goes to the sponsoring and supporting companies and institutions.

We also extend our gratitude to the colleagues supporting us in the preparation of the congress, namely the EUROREGIO Chairs Dick Botteldooren and Gijsjan van Blokland, the members of the Technical Committee Brigitte Schulte-Fortkamp and Klaus Genuit, and last but not least, the professional congress organizers at DEGA, Teresa Lehmann and Julia Schneiderheinze, and Karin Charlier and the whole staff at the Institute of Technical Acoustics of RWTH Aachen University, who suffered days and weeks of additional workload.

The international family of acoustics benefits from the presentations, which are created, presented and set to discussion (and also criticism) by you, dear participants. The program committee has tried to arrange the conference as effective and pleasant as possible for you. We wish that ICA/EUROREGIO 2019 will leave a reverberant trace of scientific knowledge, innovative ideas and products and also a permanent trace of collegial, international and interdisciplinary cooperation.

Michael Vorländer, Conference Chair
Janina Fels, Conference Co-Chair