Birds are among the most vocal of taxa and there is a wealth of research investigating how birds produce, sense, and use sounds. In this chapter, we describe how birds produce vocal sounds, and how the anatomy of vocal production varies among taxonomic groups. We also review the growing literature on the production of nonvocal sounds or sonations. We then turn to the anatomy of the avian ear and summarize the extensive literature on hearing abilities in birds. Birds rely heavily on sounds for communication both within and across species, resulting in an extraordinary diversity of sounds; here, we focus on describing how this diversity can be classified into relatively few functional categories of signals. Finally, we review the effects that noise, both natural and anthropogenic, has on the production and perception of sound signals by birds.