Sounds above 90 decibels (Decibel-dB or dBA- a measurement of the loudness or strength of sound vibration) may cause vibrations intense enough to damage the delicate sensory cells of the inner ear, especially if the sound continues for a long time. These sensory cells in the inner ear typically do not recover once damaged; once they are gone, they are never replaced.
For instance, daily activities such as speech take place in the 60-80 dB range (the GREEN zone) and are safe without hearing loss for up to 12 hours. Alternatively, a jackhammer produces a sustained noise level of 120 dB, the noise from a large truck can peak at around 90 dB, and the average noise level inside the cabin of an airplane can be between 90-100 dB over the duration of your flight.
If you turn up your iPod or car radio to drown out the racket around you, you are actually blasting your ears with a dangerous level of sound. This combination of noise can cause hearing damage in a very short period of time. For further information, visit the Dangerous Decibels website.