What are the dangers of loud noises?
How can high-volume sound cause hearing loss?
The way we hear sound involves an intricate series of physical, chemical and electrical activity within our ears. An integral part of our ability to hear lies in the tiny hair-like cells within the cochlea. As sound vibrations enter the ear, these cells – called stereocilia – will bend. This bending action opens pores within the cells, allowing ions into the cells and creating an electrical charge to stimulate our auditory nerve so sound can be perceived. Once the sound stops the hair-like cells will spring back into a straight position. These stereocilia cells, however, are delicate structures that when damaged can start a domino effect leading to hearing loss. Loud noises are one of the ways these tiny cells can lose their bounce.
Noise-induced hearing loss (NIHL) can be caused by either a single exposure to a deafening sound or longer-term exposure to loud noise such as music. These exposures will damage the stereocilia’s ability to bend and ultimately limit if not remove the electrical signals sent to the auditory nerves and subsequently the sound being integrated by the brain. A normal conversation is held at about 60 decibels, but if exposed to sounds over 90 decibels every day chronic hearing loss may occur.
Before the band begins to play the sound-translating hair-like cells are active and stand relatively straight.
After being bombarded with sound, these cells wilt and in some instances are damaged, creating that post-party buzzing sound.
Switching electricity for light
Researchers at the University Medical Center Göttingen, Germany, have used optical fibre technology to restore hearing in gerbils, a breakthrough that could improve on current technology used to combat hearing loss, such as cochlear implants. These implants have revolutionised medical treatment for those who are hearing impaired. Modern-day cochlear implants convert sound into electrical signals in the same way as the natural ear but are still somewhat sensitive to all surrounding sounds. The German research team have taken on this challenge, and rather than producing an electric signal, their device creates light. With the aid of a virus-carrying gene encoding for light sensitivity, hearing- impaired gerbil test subjects were found to respond to sound with the use of the optical implant.
This article was originally published in How It Works issue 118
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