It has been shown that, apart from the ear's high selectivity for sounds of different frequency/pitch, amplitude modulation (fast sound level fluctuations) and sound localization are important mechanisms for object separation. In fact, it has to seperate auditory objects and selectively amplify them. A hearing aid that uniformly amplifies all acoustic signals does not help in a cocktail party situation. hearing aids) can not copy the abilities of the human ear yet. The available processing power advances almost as fast as the cpu performance found in home computers.Ĭomputers (e.g. Since then, hearing aids have been in constant development and producers meanwhile offer fully digital hearing aids that allow for a complex processing of acoustic signals. Thus, the introduction of the digital hearing aid can be regarded as a leap in technology. Not even mobile phones, that were regarded as a marvel of technology, had this efficiency. Despite the fact that digital technology was already widely spread, the possibility to fit a processing unit and digital circuitry into the confined space of a hearing aid, with minimal energy consumption, came as a surprise for the hearing aid industry. The first hearing aid processing acoustic signals digitally was presented in 1996.

The trend continues upwards, since life expectancy in our society increases continually and hearing loss is a typical age-related problem.

15 percent of all Germans suffer from inner-ear hearing loss. Trying to lip read what was said is futile, as ear and brain are not able to cope with the complex acoustic environment. Everbody is talking, in pairs or in larger groups - but some people don`t understand, what their opposite says. Imagine a cocktail party: Voices, clinking glasses, discreet music. Hearing aids can restore this ability only to some extent, since the complex object-forming processes have not yet been successfully replicated technically. They can only communicate when no other distracting sound sources are present. With hard-of-hearing persons, however, this is different. With healthy persons, scene analysis works flawlessly. One of the biggest mystery is the fact that humans are able to filter out the voice of a talking person from a variety of sound sources (other persons, barking dogs, passing cars. Almost everyone is oblivious of the complex processing in the ear and brain that transform sound waves into 'heard' information. Physiology and Modeling of Auditory Perception.Department of Medical Physics and Acoustics.

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Auditory signal path