Bimodal, CROS and Severe Profound Hearing Loss Study

Inclusion Criteria: * Participant is willing and able to give informed consent for participation in the study. * Male or Female, aged 18 years or above. * Consistent unilateral user of an Advanced Bionics cochlear implant and a contralateral hearing aid for at least 6 months, ideally 12 months, and Bilateral severe to profound hearing loss (meeting NICE criteria for implantation-2009). (group 1) * Consistent unilateral user of an Advanced Bionics cochlear implant for at least 6 months and ideally 12 months, with no useful contralateral hearing (group 2) * Consistent user of bilateral hearing aids for at least six months (group 3) and bilateral severe profound hearing loss (80dB or worse at 2000 and 4000 Hz with speech discrimination of at least 50% IHR sentences live voice at 60dBA) * First language English * Post-lingual onset of severe to profound hearing loss * No other handicaps that would interfere with participation in the study in the opinion of the Principle Investigator Exclusion Criteria: * Unstable cochlear implant or hearing aid fitting * Using medication in an intermittent manner that might influence hearing levels * Cognitive or psychological challenges that might lead to variations in attention