The introduction of high quality digital audio media such as the compact disc and digital audio tape has greatly raised expectations about sound quality in all types of recordings. Combined with a recent upsurge in interest in historical and archive recordings of music, speech and other audio material, the restoration of degraded sources has become an increasingly important field. Containing research previously unpublished in any form, applications of modern signal processing techniques to audio restoration are presented here in a comprehensive and authoritative text. As well as providing a wide coverage of existing methodologies the authors also analyse both current areas of research and future trends. In addition the text is supported by introductory material on digital signal processing. Aimed at researchers in signal processing, at communications industries and at music companies and media libraries wishing to remarket or use archive sound recordings, this is a unique and essential study of audio restoration techniques.