Dolphin vocalizations can only be understood with direct interactions using underwater whistles. This free Android app is for that:

DC Dolphin Communicator 2019

https://play.google.com/store/apps/details?id=sm.app.dc&hl=en_CA

With source code from:

https://gitlab.com/leafyseadragon/android-dolphin-comm-app

https://gitlab.com/leafyseadragon/android-acoustic-lib