Tinnitus, the perception of sound without an external source is common, affecting around 10% of adults. Tinnitus can seriously reduce quality of life, for example through annoyance, sleep deprivation, anxiety and depression. Since tinnitus is associated with hearing loss, a common theory for the underlying cause is that the brain reacts to the hearing loss by ‘turning up the volume’. We aim to identify abnormal brain activity associated with tinnitus following hearing loss due to surgical procedures to remove a tumour on the hearing nerve, information that is essential for understanding exactly how the brain turns up the volume.