i. accessing big datasets of existing HA user data from the EVOTION clinical partners (UCL/UCLH and GST in the UK; OTICON in Denmark) ii. collection of prospective HA user data who will be recruited to the prospective EVOTION study and who will undergo some additional assessments iii. collection of real time dynamic data of the human participant HA users who will be given a smart phone with different apps (auditory tests; auditory training), sensors (recording of heart rate, blood pressure, respiratory rate etc.) and smart HAs (recording environmental factors such as noise levels, type of noise etc.) so that real life contextual factors that affect HA usage and outcome can be identified.