The two most common types of hearing loss are caused by aging and exposure to excessive noise. In both cases, the hairs or nerve cells in the cochlea that are responsible for sending sound signals to the brain are progressively affected.

When the hairs or nerve cells become damaged or missing, the electrical brain signals are not transmitted effectively and sounds are not processed as well. At this point, it may be difficult to recognize words in the presence of background noise and higher pitched tones often become muffled.

Despite similarities in the effects of age- and noise-related hearing loss, however, a new study from the Society for Neuroscience has found that these two conditions impact sound processing in the brain on different timescales. The research suggests that each type of hearing loss should have its own unique treatment.

A research team led by Michael Heinz and Kenneth Henry set out to observe how the auditory nerve encodes sounds. The experts used a chinchilla model of age-related hearing loss, which is the traditional animal model for most types of research related to the ear. This is due to the fact that chinchillas have inner ear anatomy that is very similar to humans.

Next, the researchers compared their results to data from a chinchilla model of noise-induced hearing damage. They found that the same level of sound sensitivity loss caused more severe processing changes in the auditory nerve of chinchillas with noise-induced hearing loss compared to those with age-related hearing loss.

The study revealed that mild noise-induced hearing loss caused the same amount of processing impairment as moderate to severe age-related hearing loss. The findings emphasize the need for hearing-safety awareness, as well as for more customized treatments of hearing loss.