We organized a number of activities through which we learned together about the basics of sound propagation (through the air), the audible frequency range and how our hearing "ages" (presbycusis), Fourier analysis, and even a bit of machine learning for automatic sound recognition!
As a researcher, I feel it is both a duty and a privilege to get young people interested and excited about science, and especially girls because we need more women in science!
And if that wasn't sufficiently rewarding already, at the end of the day we each got a box of delicious cookies too :)