When using headphones, personal music players can subject listeners to noise levels similar to those of jet engines. Noise levels exceeding 110dB are known to cause hearing problems such as temporary hearing loss and tinnitus (ringing in the ears). But for the first time the underlying cell damage has been observed.
Turning the volume up too high on your headphones can damage the coating of the ears' nerve cells, leading to temporary hearing loss, scientists from the University of Leicester in the UK have now shown.
Coated nerve cells
Nerve cells that carry electrical signals from the ears to the brain have a coating called the myelin sheath, which helps the electrical signals travel along the cell. Exposure to loud noises, i.e. noise over 110dB, can strip the cells of this coating, disrupting the electrical signals. This means the nerves can no longer efficiently transmit information from the ears to the brain.
However, the coating surrounding the nerve cells can reform, letting the cells function again as normal. This means hearing loss can be temporary, and full hearing can return.
Reversible hearing loss
University of Leicester researcher Dr Martine Hamann of the Department of Cell Physiology and Pharmacology, who led the study, said:
"We now understand why hearing loss can be reversible in certain cases. We showed that the sheath around the auditory nerve is lost in about half of the cells we looked at, a bit like stripping the electrical cable linking an amplifier to the loudspeaker. The effect is reversible and after three months, hearing has recovered and so has the sheath around the auditory nerve."
The study has been published in the Proceedings of the National Academy of Sciences.