Noise induced hearing loss (NIHL)
Noise induced hearing loss (NIHL) is hearing loss that is caused by loud sound. It usually occurs after years and repeated exposure to loud noise. It can also occur after a single high intensity loud noise incident such as an explosion.
Loud noise causes acoustic trauma to the hair cells in the cochlea. The hair cells can die and be replaced by scar tissue. When a hair cell is lost it cannot regenerate and is lost forever. Loud noise may also damage the nerve junctions of the cochlear nerve.
NIHL usually occurs in both ears and develop over time. It may not be noticed at first. Patients may later on develop tinnitus and have difficulty hearing certain frequency sounds like “s”. They will then experience problems in following conversations in the presence of back ground noise.
When exposed to sudden high intensity sound, a patient may experience sudden loss of hearing, pain, bleeding from the ear, dizziness and tinnitus. With explosions the transfer of energy via a pressure wave can cause barotrauma such as rupture of the eardrum.
NIHL in the workplace is also called occupational hearing loss and is the most common occupational disease in the world. Mineworkers, factory workers military personnel and musicians are mostly affected. Programs are instituted all over the world in nearly every industry to prevent and address occupational hearing loss.
NIHL should be prevented. Education and knowing about the risk, reducing the source of the noise, reducing the time of exposure and wearing ear protection all helps. There are different earplugs, caps, muffs and noise protectors on the market. Certain noise protectors will conduct sound and allow communication yet filter out certain loud harmful noises.
Unfortunately some people are more prone to develop damage due to loud noise than others. For patients with established hearing loss, FM systems, hearing aids or even cochlear implantation (CI) may improve the hearing.
Medication that may reduce the oxidative stress of the cochlea if taken before and after noise exposure is currently investigated. This may also benefit people with occasional exposure such as those attending music concerts or hunting. Stem cell therapy to replace lost hair cells is not yet available.