A computer controlled digital master hearing aid

The design and implementation of a computer-controlled digital master hearing aid (DMHA) has provided a flexible and versatile research tool for research in speech processing algorithms to benefit the hearing impaired. The system includes programmable antialiasing and reconstruction filters, a digital signal processing board using the TMS320C25 chip, and programmable attenuators and switches. All elements in the system are under software control by an IBM PC. For a recent study on subjects with steeply sloping hearing losses, software has been developed to fit the DMHA to each individual using 253-tap FIR digital filters. The system has been used with success for this study, providing higher flexibility, precise fitting of the hearing aid and a large dynamic range (90 dB). It can be used to implement and evaluate new algorithms that cannot be implemented with analog circuits, such as enhancement of speech in noise and speech feature extraction