The purpose of this study is to investigate the functional benefits of frequency compression vs no frequency compression or fitted to hearing loss in severe-profound hearing impaired adults with high frequency hearing losses. Thus, assessing whether hearing aids for this patient population can be adapted to improve speech perception.

Frequency compression is a feature available on some digital hearing aids, which is aimed at increasing the audibility of high frequency sounds. It works by taking sounds above a fixed start frequency and compresses it into lower frequencies where residual hearing is better.

Inclusion Criteria:

1. Participants must be over 18 years of age- This study is looking at the use of frequency compression & its effects of speech perception in adults.
2. No ear surgery that would make it impossible to fit a hearing aid- To ensure limited confounding variables.
3. No history of ear surgery within the last 12 months- To ensure limited confounding variables.
4. No history of ear infection(s) within the last 6 months- To ensure no contraindications and limited confounding variables to testing.
5. No otoscopic abnormality making it impossible to fit a hearing aid- To ensure no contraindications to testing.
6. Bilateral severe-profound hearing impairment with air conduction thresholds >71dBHL within the frequency range of 250Hz to 4 kHz- To analyse the effects of frequency compression on speech perception within this patient population.
7. Post lingual deafness, with good spoken English- To ensure reliability of speech testing.
8. Previous bilateral digital hearing aid experience (6+ months)- To ensure limited confounding variables.
9. Written consent required.

Exclusion Criteria:

1. Participants under the age of 18 years.
2. History of ear surgery making it impossible to fit a hearing aid.
3. History of ear surgery within the last 12 months.