There have been many changes and developments since the publication of the first edition of Principles of Hearing Aid Audiology. The text of the second edition has been updated and extended throughout to reflect these changes, including the important changes to the Hearing Aid Council regulations and in British Standards. New tests, new prescriptive algorithms, developments in our understanding of how the cochlea works, open jaw impressions - all these new areas are now included. There is also a complete new chapter on digital hearing aids. Principles of Hearing Aid Audiology continues to be the one book which provides comprehensive and up-to-date material on hearing aid audiology for those in training or who wish to revise and update their knowledge. It is a book that is both readable and relevant.