Similar noise levels at the same workplace can affect people differently. In order to find out which workers are most likely to suffer from noise induced hearing loss, Austrian researchers from the Institute of Environmental Health in Vienna, Austria, have developed a simple test.
The test measures temporary hearing loss, also known as temporary threshold shift (TTS). By doing this, it is possible to tell how fast the inner ear cells recover after being exposed to noise. The speed of recovery is crucial in determining the level of susceptibility to noise induced hearing loss.
Noise exposure and hearing loss
The test exposes participants to frequencies of between 200-500 Hertz, about 100 decibels. After this, an audiogram (a description of hearing ability) at 4 kilohertz for 10 minutes is performed. The level of temporary hearing loss, TSS, measured after 2.5 minutes, indicates how likely the person is to suffer from permanent hearing loss (permanent threshold shift) caused by noise exposure.
The Austrian researchers measured the hearing of 125 male teenage apprentices working at a steel company. The hearing was measured at the beginning of the apprenticeship before noise exposure. After this, their hearing was tested every three to five years for a period of 13 years.
The results of the test show that 82% of the participants who were expected to have their hearing affected by noise experienced hearing loss. Of the participants who were initially expected not to be vulnerable to noise, one in two was affected.
The use of the test
The lack of accuracy in the test means that it cannot be used to assign some workers to noisy jobs and exclude others. Instead, the results can be used “for improving counseling especially concerning use of hearing protectors and for a tighter schedule for hearing tests,” one of the authors, Dr. Michael Kundi says to Reuters.
The study was published in Occupational and Environmental Medicine.