Background: Various different hearing systems are available for device-supported hearing rehabilitation of patients with mixed hearing loss. Using the recently introduced objective comparison criterion "maximum output" (i.e., the maximum output level of a hearing device), the indications for different hearing devices can be compared.
Objective: This article reviews important terms such as gain, dynamic range, and maximum output level-all of which are relevant for the selection of a hearing device. The experimental part of this study compares all currently available hearing devices and determines the range of their indication with respect to the maximum bone-conduction hearing threshold.
Materials and methods: The maximum frequency-specific output levels reported in the literature for the Baha Cordelle 2, the Sophono Alpha 2, and the Bonebridge (measured at the skull simulator), as well as those of the Codacs and the Soundbridge (in-vivo measurements) are compared to the maximum output levels given in the datasheets of the BP110 Power, the Baha Cordelle 2, the Bonebridge, the Codacs, the Ponto Pro Power, and the Sophono Alpha 2. Using appropriate correction factors, the maximum dynamic range and thus the maximum indication based on the bone-conduction threshold was determined.
Results: In patients with mild sensorineural hearing loss, passive transcutaneous hearing or Bonebridge implants can achieve good audiological results. In the transition region to moderate hearing loss, percutaneous devices are applicable. Combined hearing loss with more pronounced sensorineural hearing loss is best treated with a Soundbridge or Codacs implant. In the latter case, the cochlear potential for speech recognition has to be explored and, where appropriate, cochlear implants considered as an alternative.
Keywords: Active hearing implant; Bone conduction; Gain; Maximum output; Mixed hearing loss.