Preface.- Introduction to Hearing Aids.- Population of Hearing Aid Candidates.- Hearing Aid Transducers.- Speech Perception and Hearing Aids.- Hearing Aid Signal Processing.- Spatial Hearing and Interactions with Hearing Aids.- Wireless Connectivity and Patient Interface.- Fitting and Clinical Verification of Hearing Aid Performance.- Validation of Hearing Aid Performance in Everyday Life.- Listening to Music through Hearing Aids.- Future Directions for Hearing Aid Development.