ABSTRACT
A new hearing aid shell technology has been introduced: A laser scans the impression
taken by an audiologist and the data are used to create a 3D image of the impression
on the computer screen. This image is used to design a shell with a vent and the receiver
bore. When the design is finished, another computer builds the shell from nylon powder
or liquid.
This technology duplicates the shape of the impression into the shell with extreme
accuracy. It would be expected that hearing aids made with such a shell would have
the perfect fit and would not require modifications and remakes. However, such an
assumption would be incorrect. In fact, all the problems common with the traditional
shells also are plaguing the new electronic shell: acoustic feedback, loose fit, discomfort,
and lack of secure fit. This article explains how the accuracy of an ear impression
taken by the audiologist contributes to the fitting of the shell, and concludes that
ear impressions taken with a higher viscosity silicone and the patient's mouth open
are the most appropriate to build e-shells.
KEYWORDS
Human ear - ear impression - hearing aid shell
