Claus Nielsen

Research Audiologist

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Earmoulds and In-The-Ear hearing aid shells are often made of hard acrylic material, which does not accommodate shape changes of the ear canal occurring due to jaw action and head movements. This may cause discomfort in the ear - and acoustical feedback in the hearing aid.

Investigation of the dynamics of the ear and ear canal

The baseline data of the study were laser-scanned ear impressions taken in four different conditions

• Jaw in relaxed position
• With a bite-block in the mouth (similar to yawning)
• Head turned to the side away from the ear
• Head bowed down

Data from 30 normal-hearing ears was collected in the pilot study, while data from 42 hearing-aid users was collected in the main study. The hearing-aid users also completed an 8-item questionnaire covering physical fit, physical comfort, and acoustical feedback. Separate statistical shape models were built for each of the four conditions.


Confirming expectations and learning new things

As anticipated, the analysis of the shape models revealed that men have larger ears than women. Examination of the ear-canal deformations showed them to be larger in men than in women. Generally the largest deformations were discovered in the downward-facing part of the ear canal. Finally, a relation was found between the amount of ear deformation and how often acoustical feedback was experienced.

Further reading

S. Darkner (2008). Shape and Deformation Analysis of the Human Ear Canal. Informatics and Mathematical Modeling, Technical University of Denmark, building 321, Richard Petersens Plads, DK-2800 Kgs. Lyngby.

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    Ph.D. thesis

    Shape and deformation analysis