The project studied the hearing ability of Humboldt penguins. The hearing ability of the penguins was determined psychoacoustically and by auditory evoked potentials (AEP). The results show that penguins hear best between 1 and 4 kHz in air. In addition, an animal audiogram database was created to facilitate comparison between the published audiograms of different aquatic animals. Penguins responded with a surprisingly low response threshold to sound stimuli in underwater playback experiments. This project has laid the foundation for future studies on the hearing capacity of diving birds, contributing to a greater understanding of how marine birds are affected by underwater noise.