Indications of hearing levels for cartilage conduction hearing aids: Evaluation using 2 cm³ coupler and an artificial mastoid

Abstract

The indications for cartilage conduction (CC) hearing aids have not been clearly determined. In this study, we evaluated CC hearing aids using standard methods for air and bone conduction (AC and BC) hearing aids, after which we estimated the indications for CC hearing aids. The two evaluation methods were as follows: 1) the vibration emitted from the transducer was translated into sound and the output level was measured using a 2 cm³ copular (as with AC hearing aids), and 2) the vibration emitted from the transducer was evaluated using an artificial mastoid (as with BC hearing aids). In CC, the transmission pathway to the cochlea depends on ear structure. When the sound is transmitted via the eardrum, the output level should be evaluated using the AC method. In this case, CC hearing aids could provide adequate amplification for a mild to moderate hearing loss. Furthermore, CC hearing aids can be used in individuals with severe hearing loss when the audiogram shows loss of low to middle tones. In other ears, the output level should be evaluated using the BC method. Here, CC hearing aids can be effectively used in ears with normal BC thresholds.