Studies with Digital Hearing Aids.

Digital hearing aids offer many advantages over conventional hearing aids. These include signal-processing capabilities that are superior to those of a conventional analog hearing aid, methods of signal-processing and control that are unique to digital systems and which cannot be implemented in conventional analog hearing aids, and innovative new techniques that are changing our way of thinking about hearing aids. An example of the first of these advantages is the extremely high precision with which the frequency-gain characteristic can be specified and the use of this capability to study the effects of frequency response irregularities commonly encountered with hearing aids. An example of the second advantage is the use of memory and logical operations in the implementation of multivariate adaptive paired-comparison techniques for more effective hearing-aid prescription. Another example is the use of powerful new signal processing techniques for noise reduction. The third advantage is the most important. The digital hearing aid can be viewed as a generalized hearing instrument which can be used for simulation, testing and prescription, as well as amplification. The use of the digital hearing aid as a simulator of other hearing aids is discussed and an illustrative example provided in which a new form of amplitude compression, orthogonal-polynomial compression, has been simulated using a digital master hearing aid.