The annual Open Seminar on Acoustics is the largest conference in Poland gathering leading Polish acousticians for over sixty years. It is organized cyclically by subsequent divisions of the Polish Acoustic Society – in 2021 by the Krakow Division. During the Conference, works from all fields of acoustics are presented. The aim of the conference is to exchange scientific experience in the field of acoustics, promote science and integrate specialists from various fields related to acoustics. The Conference plays an integrating role for the environment of Polish acousticians as well as more and more often guestes from abroad. This enables exchange of ideas, implementation of new research techniques and opens new application areas. A special session will be organized to celebrate the International Year of Sound 2020-2021.