Radiotherapy and combined radiotherapy and chemotherapy are used to treat most tumours in the head and neck region. Unfortunately, these treatments often result in hearing loss and tinnitus that has a negative impact on quality of life. This study will use a battery of sensitive tests, including measures of hair cell and neural function, before and after treatment, to measure the effects of these treatments on auditory function. The results will be compared with the individual radiotherapy dose characteristics, using state-of-the-art data mining technology, to identify the auditory substructures that are most sensitive to radiation with respect to the effects on auditory function. The data will provide the basis for new dose constraints to limit radiation doses to any identified substructures and to minimise loss in hearing ability for patients undergoing treatment for head and neck cancer.