Description
Book SynopsisThe first book available on the subject, Digital Hearing Aids provides an overview of the signal-processing strategies implemented in modern digital hearing aids. Algorithms ranging from dynamic-range compression and directional microphones to sound classification and binaural noise suppression are clearly explained. The basic equations describing the signal-processing algorithms are presented along with full explanations for those less comfortable with the mathematics, and each processing strategy is accompanied by a summary of its effectiveness. The text is intended for a graduate audiology course in hearing aids and hearing-aid technology.
Trade ReviewH. Martin, Journal of Laryngology and Otology, (2009): "I was a little daunted when I flicked thought the book, due to the many mathematical equations and circuit diagrams ... However, I need not have worried, as the book is very well written and it is possible to follow the explanations without fully appreciating the details of the equations. ... An excellent reference resource for those involved in selecting and programming hearing aids and counselling users in the limitations of their aids." Denise Hoysack, AuD, CCC-A, Otology & Neurotology, (2010): "The author does a good job of explaining the complexities involved, the capabilities, and constraints of signal processing. Additionally, the book is littered with mathematical equations, graphs, charts, and figures to ease the difficulties of understanding the concepts discussed." Ron Brouillette, PhD, Advisory Group on the Prevention of Hearing Impairments, (2009): "... The text is easily understood and complete with specifics useful to those who desire to stay current with digital hearing aids technology."
Table of ContentsPreface Hearing-Aid Technology Types of Hearing Aids From Analog to Digital Digital Circuit Components Batteries Concluding Remarks References Signal Processing Basics Signal and System Properties Discrete Fourier Transform Filters and Filter Banks Block Processing Digital System Concerns Concluding Remarks References The Electroacoustic System Hearing Aid System Head and Ear Microphone and Receiver Vent Acoustics Occlusion Effect Concluding Remarks References Directional Microphones Hearing-Aid Microphones Directional Response Patterns Frequency Response Magnitude Frequency Response Microphone Mismatch Interaction with Vents Microphone Noise Microphones on the Head Microphone Performance Indices Rooms and Reverberation Benefit in the Real World Concluding Remarks References Adaptive and Multi-Microphone Arrays Two-Microphone Adaptive Array Delay-And-Sum Beamforming Adaptive Arrays Superdirective Arrays Widely-Spaced Arrays Array Benefits Concluding Remarks References Wind Noise Turbulence Hearing-Aid Measurements Signal Characteristics Wind-Noise Reduction Concluding Remarks References Feedback Cancellation The Feedback System Gain-Reduction Solutions Adaptive Feedback Cancellation Processing Limitations Concluding Remarks References Dynamic-Range Compression Does Compression Help? Algorithm Design Concerns Single-Channel Compression Multi-Channel Compression Frequency-Domain Compression Frequency Warping Concluding Remarks References Single-Microphone Noise Suppression Properties of Speech and Noise Signals Low-Level Expansion Envelope Valley Tracking Bandwidth Reduction Envelope Modulation Filters Concluding Remarks References Spectral Subtraction Noise Estimation Wiener Filter Spectral Subtraction Algorithm Effectiveness Concluding Remarks References Spectral Contrast Enhancement Auditory Filters in the Damaged Cochlea Spectral Valley Suppression Spectral Contrast Modification Excess Upward Spread of Masking F2/F1 Ratio Processing Comparison Combining Spectral Contrast Enhancement with Compression Concluding Remarks References Sound Classification The Rationale for Classification Signal Features Feature Selection Classifier Algorithms Classification Examples Concluding Remarks References Binaural Signal Processing The "Cocktail Party" Problem Signal Transmission Binaural Compression Binaural Noise Suppression Dichotic Band Splitting Concluding Remarks References Index
