We are exposed to sound all day everyday. Especially dangerous is the so called "leisure noise". In this case we perceive the sound level mostly as comfortable although it reaches incredible dimensions. We also are exposed to impact noise that we consider is not loud enough to affect our hearing or "are used to it, and it's ok".

Hearing damages caused by noise are vicious. Because hearing loss caused by noise influence is only rarely perceived indirectly. Noise damages the hearing slowly and unrecognized but steady and most of all lasting and irrevocable. The sensitive hair sense cells in the human's inner ear are pulled out due to constant noise influence.

When people have their hearing examined by an audiologist, pitch sounds between 250-8,000 Hz are routinely measured. These are tested because they are the most important for understanding speech.

More recently, some researchers have begun to look at how noise may affect hearing for the very high pitch sounds- those between 9,000 & 18,000 Hz, known as the extended high frequencies.

Research has found that some people who are exposed to loud noise have reduced hearing in the extended high frequencies, but not in the more conventional (250-8,000 Hz) frequency range. Based on these findings, it has been suggested that a noise induced hearing loss may be detectable at an earlier stage by testing hearing in the extended high frequencies.