Abstract
The development of hearing aids incorporates two aspects, namely, the audiological and the technical point of view. The former focuses on items like the recruitment phenomenon, the speech intelligibility of hearing-impaired persons, or just on the question of hearing comfort. Concerning these subjects, different algorithms intending to improve the hearing ability are presented in this paper. These are automatic gain controls, directional microphones, and noise reduction algorithms. Besides the audiological point of view, there are several purely technical problems which have to be solved. An important one is the acoustic feedback. Another instance is the proper automatic control of all hearing aid components by means of a classification unit. In addition to an overview of state-of-the-art algorithms, this paper focuses on future trends.
Highlights
Driven by the continuous progress in the semiconductor technology, today’s high-end digital hearing aids offer powerful digital signal processing on which this paper focuses
Compared to conventional directional microphones utilizing a single diaphragm with two separate sound inlet ports, the advantage of this approach is that it allows to automatically match microphone sensitivities and that the user can switch to an omnidirectional characteristic, when the direction of the target signal differs from the assumed zerodegree front direction, for example, when having a conversation in a car
The development of hearing aids covers a wide range of different signal processing components
Summary
Driven by the continuous progress in the semiconductor technology, today’s high-end digital hearing aids offer powerful digital signal processing on which this paper focuses. The obtained monosignal is further processed separately for different frequency ranges This requires an analysis filterbank and a corresponding signal synthesis. A technically challenging problem of hearing aids is the risk of acoustic feedback that is provoked by strong signal amplification in combination with microphones and receiver.
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