Sounds that are actually produced by healthy ears allow researchers and clinicians to study hearing and cochlear function noninvasively in both animals and humans. This book presents the first serious review of the biological basis of these otoacoustic emissions. Active processes, such as those in hair cells that produce emissions, represent a burgeoning and important area of sensory research. By providing a basis for understanding how and why otoacoustic emissions testing works through a basic understanding of general hearing processes, this volume will also interest clinicians, particularly otolaryngologists and audiologists.