Open Versus Closed Hearing-Aid Fittings: A Literature Review of Both Fitting Approaches

Abstract

One of the main issues in hearing-aid fittings is the abnormal perception of the user's own voice as too loud, "boomy," or "hollow." This phenomenon known as the occlusion effect be reduced by large vents in the earmolds or by open-fit hearing aids. This review provides an overview of publications related to open and closed hearing-aid fittings. First, the occlusion effect and its consequences for perception while using hearing aids are described. Then, the advantages and disadvantages of open compared with closed fittings and their impact on the fitting process are addressed. The advantages include less occlusion, improved own-voice perception and sound quality, and increased localization performance. The disadvantages associated with open-fit hearing aids include reduced benefits of directional microphones and noise reduction, as well as less compression and less available gain before feedback. The final part of this review addresses the need for new approaches to combine the advantages of open and closed hearing-aid fittings.

Keywords: earmold; hearing aid; occlusion; open fit; real-ear measurements.

Figure 1.

Sketch of an example of a vent configuration from Kuk et al. (2005a).

Figure 2.

Sketch of a “Flex-Vent™”. Medial view (left) and lateral view (right).

Figure 3.

Sketch of a “hollow” (middle) and a “solid” (right) earmold described by Kuk et al. (2009).

Figure 4.

Sketch of a “nugget” earmold described by Saile (2010).