Though we are exposed to different types of sounds all day every day in the form of music, television, radio, traffic and more, there are sounds that can be harmful to our hearing. Even if we are exposed to these harmful sounds for only a brief moment, if they are loud enough, they can affect the way we hear as a result.
When sensitive structures in the inner ear are damaged because of this, that is considered to be noise-induced hearing loss.
Sometimes its effects can be immediate, while for others, it may take a while before it starts to become noticeable. Having that said, noise-induced hearing loss isn’t always permanent for everyone.
To fully understand how loud sounds can damage our hearing, it’s important to understand exactly how we hear.
When sound waves enter the outer ear and travel through the narrow passageway called the ear canal, it then leads to the eardrum. The eardrum vibrates from the incoming soundwaves and sends those vibrations to three tiny bones inside the middle ear called the malleus, incus and stapes. These bones couple the sound vibrations from the air to the fluid vibrations held in the inner ear. An elastic partition runs from the beginning to the end of the cochlea, splitting into two parts: upper and lower. The partition is called the basilar membrane because it serves as the base.
Once the vibrations cause the fluid inside the cochlea to ripple, a traveling wave forms along the basilar membrane, in which hair cells (sensory cells) that sit atop the basilar membrane ride the wave. Lastly, the auditory nerve carries electrical signals to the brain, translating it into sounds that we are able to recognize and understand.
In turn, most noise-induced hearing loss is caused by the damage and eventual death of those hair cells. And unlike bird and amphibian hair cells, human hair cells do not grow back.