Subjective) tinnitus is a phantom perception, where a sound is perceived by the subject that cannot be objectively perceived by other observers. an estimated 9.8% of people suffer from chronic tinnitus, moreover, for 1%-3.1% of people, it severely impacts their lives, leading to anxiety, depression, and insomnia, amongst other symptoms.
Tinnitus is strongly related to hearing loss, however, the ear is likely not the sole cause of tinnitus.

Currently, the generation and progression of tinnitus is thought to be a complex multifactorial process. Although research is ongoing and a consensus is not reached yet, the most recent theories consider the following mechanism for the development of tinnitus: (1) a lack of auditory input, triggers (2) over-expression in auditory neurons in the brainstem and auditory cortex, both part of the ascending pathway, where after (3) the tinnitus signal becomes wrongly labeled as important by the brain’s medial pathway and directed to the conscious parts of the brain where it is perceived, subsequently (4) the descending pathway is unsuccessful in suppressing the generation of tinnitus.

It is hypothesized that pairing acoustic stimulation using tinnitus-matched sound with transcutaneous electrical nerve stimulation of the vagus nerve can teach the brain to associate the distressing tinnitus sound with the de-stressing stimulation of the vagus nerve. Over time it is expected that the tinnitus sound will be labeled as unimportant by the medial pathway and is thus consequentially suppressed.

To investigate this hypothesis a bimodal stimulator is required that can combine acoustic stimulation and transcutaneous electrical vagus nerve stimulation. The device should be easy to use and safe. The specific focus of this thesis report was to design the electronic hardware for electrical stimulation and power management and implement various safety features.

From testing the stimulation output it could be concluded that the device is successfully able to produce the electrical pulse pattern and potentially any other electrical pattern. Following a risk assessment, and analyzing the safety of the device, it was concluded that the device can be used to test the efficacy of the proposed treatment, given that it is used in the prescribed circumstances and that the user is aware of the risks. Furthermore, it was shown that the device was able to stimulate the vagus nerve. Overall, the device was easy to use and was able to pair acoustic and electrical stimulation.