A photo of the ear of an older person with a hearing aid. Photo by rawpixel.com from Pexels.
Read about research into the inner ear:
N. R. Gough, A Key to Restoring Age-Related Hearing Loss. BioSerendipity (21 November 2018) https://www.bioserendipity.com/a-key-to-restoring-age-related-hearing-loss