The course focuses on the knowledge acquired about how the auditory sensory system processes the various components of acoustic messages (including voice and music): how this system extracts and codes the physical parameters of sounds and their statistical regularities, localizes sound sources and forms a percept of sound objects that can be included in a multisensory representation of the auditory scene and generate behavior. The last twenty years have been marked by the discovery of the molecular mechanisms underlying the functioning of the auditory system, essentially those of the sensory cells and their associated neurons. Based on a genetic approach, this deciphering has led to the development of an integrative vision of physical, physiological and molecular data. The pathophysiology of hearing impairment, whether hereditary or environmental and mainly noise-induced, was jointly documented, paving the way for the search for curative therapies. Two complementary lines of research have been explored in this course: how to "repair" the auditory sensory organ, and how to solicit brain plasticity to enable this repair to succeed.