Maximilian Eliasson and Benjamin Blomqvist, Electrical Engineering

Abstract:
This thesis documents the process of developing and testing a prototype bone conduction stimulator for ankle audiometry using the novel B250 transducer which is developed by the Biomedical signals and systems research group. The device is intended to be used for screening for conductive hyperacusis (heightened sensitivity to internal bodily sounds), a symptom of superior canal dehiscence syndrome (SCDS). SCDS originates from an opening in the temporal bone overlying the superior canal of the vestibular labyrinth and results in symptoms such as vertigo and conductive hyperacusis.

The project utilises the B250 bone conduction transducer and focuses on the development of a driver circuit and enclosure of a prototype ankle audiometer. Specifically, the device must have a signal stability and usability that is better than, or equal to pre-existing tools. Since the device is intended to be certified as a medical device, care was taken to comply with relevant standards. The device is required to be able to stimulate the patient at five different intensity levels with a pure tone of around 250 Hz where the B250 has its peak in frequency response. A secondary goal was to construct a method to attach the transducer to
the patient at a constant force of 10 N.

The resulting prototype is able to stimulate at 244.7 Hz with low harmonic distortion (below 2%) and within the margin of error for all the desired intensity levels. The circuit and batteries are enclosed within a small portable plastic box. For further improvement and simplification of the ankle audiometry method, a solution to construct a patient attachment is also proposed in the thesis.