Non-linear Frequency Compared to Conventional Processing in Patients With and Without Cochlear Dead Regions.

The investigators are interested in an additional hearing aid feature called non-linear frequency compression (NLFC). This aims to improve audibility of high frequency sounds by converting them into lower frequencies and has been shown to benefit those with moderate-severe sensorineural hearing loss (SNHL). Cochlear dead regions (DRs) are areas of the inner hearing organ (the cochlea) where there is little or no function and are commonly found in regions responsible for detecting high pitched (frequency) sounds. Not all people with hearing loss have DRs. The investigators would like to determine whether based on the presence or absence of DRs, patients with moderate-severe SNHL perform better or prefer their hearing aids programmed conventionally, or with NLFC activated. To do this, two participant groups will be created based on findings from the threshold equalising noise (TEN) test which identifies cochlear DRs. Two participant groups will be created; one group with DRs and one group without DRs. All participants will receive two hearing aids and will wear these programmed conventionally for \~six weeks and with NLFC activated for \~six weeks in a counterbalanced manner. Following each condition, participants will complete a questionnaire and various speech tests will be performed. This involves participants repeating sentences, words or speech sounds they hear from a speaker in quiet and in the presence of background noise. Individuals' scores will be calculated for each test and their performance when NLFC was activated and deactivated will be compared. This will be analysed alongside the questionnaire data to compare the 'DR' and 'no DR' group in both conditions. Findings may help to determine whether NLFC should be activated for all moderate-severe SNHL patients, or just those with DRs, helping clinicians to optimise hearing aid settings for patients.