From children to adults: How binaural cues and ear canal impedances grow

Fels, Janina; Vorländer, Michael (Thesis advisor)

Berlin : Logos-Verl. (2008)
Dissertation / PhD Thesis

In: Aachener Beiträge zur technischen Akustik 5
Page(s)/Article-Nr.: VIII, 157 S. : Ill., graph. Darst.

Abstract

In this thesis the growth-dependency of head-related transfer functions and their resulting parameters (interaural time and level differences) are analyzed as well as ear canal impedances. Custom-designed measurements for children were developed which made it possible to obtain anthropometric data from different kinds of subjects, ranging from infants to adults. The obtained data is statistically evaluated with regard to its influence on binaural cues and ear canal impedances with the help of suitable simulation- and measurement techniques. It becomes evident that children and adults differ tremendously as far as their respective head-related transfer functions are concerned. Furthermore it turns out that the head-related transfer function of a child cannot be obtained by scaling down the dimensions of an adult head. Differences in the anatomy of children and adults thus result in different binaural cues. The individual anthropometric parameters, however, affect the binaural cues to a varying extent. In this thesis the most important anthropometric parameter with regard to their influence on binaural cues, are determined. Ear canal impedances are undergoing certain changes as well while children are growing up and finally reach adulthood. This thesis presents for the first time, the age-related development of data that is most decisive for the impedances. These new findings open up new possibilities to develop artificial child heads and couplers for hearing aids that are suitable for children. Thus, improvements in certain fields of applications such as the development and fitting of hearing aids for children are now possible and measurement techniques that are used for classroom acoustics can now be optimized significantly as well. Moreover, these new findings are vital when it comes to re-evaluating standardized artificial heads.

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