Improved methods for verification of bone conduction hearing devices

Research Project, 2018 –

For patients who are rehabilitated with bone conduction hearing aids, there is a clinical need to be able to measure the patient's audibility. Currently, there is a well-developed method for this only when it comes to air conduction hearing aids, but for bone conduction hearing aids, this method is not possible to use. Instead, one has had to rely on the manufacturer's recommendations or the patient's subjective assessments and audiometric tests.

In a collaboration between Chalmers and Sahlgrenska, we have developed a new method to objectively measure the audibility of patients with bone conduction hearing aids. It involves testing the hearing aid on the patient in a sound field and at the same time using a skin microphone in the forehead that can pick up the sound generated from the vibrations in the skull bone. The sound pressure in the forehead is measured both at the hearing threshold and at the maximum output level of the device. A synthetic speech is then played to see if this is in the patient's so-called dynamic range, which is between the hearing thresholds and the maximum output level of the device. If it turns out that the speech is not completely in the dynamic range, adjustments should be made to the fitting of the device to better suit the individual, or alternatively, change to a louder device if the maximum sound level is not high enough. In this way, a more objective, individualized programming of bone conduction hearing aids can be created.