From the Delmar/Cengage Web site:

"This book is devoted to the acoustical principles that underlie the design and fitting of hearing aids. It includes coverage of basic acoustics, including a full, but mostly nonmathematical discussion of the decibel unit, air-coulmn and Helmoltz acoustical resonance, horns, the effect of the acoustical transmission path of the ear on hearing-aid response, psychoacoustics, amplification systems of hearing aids (including signal processing and class D and digital circuitry), and noise-reduction system. These subjects are discussed in terms of their specific applications to the design and fitting of hearing aids. The book presents the information in simple understandable terms."