Earphones 'as dangerous as noise from jet engines'
Earphones and headphones have for the first time been shown to damage the coating of nerve cells, leading to temporary deafness.
While noises louder than 110 decibels are known to cause hearing problems such as temporary deafness and tinnitus - ringing in the ears - it's the first time the underlying cell damage has been observed.
Earphones or headphones on personal music players can cause as much damage as jet engines, the University of Leicester researchers say.
"The research allows us to understand the pathway from exposure to loud noises to hearing loss," says researcher Dr Martine Hamann.
"Dissecting the cellular mechanisms underlying this condition is likely to bring a very significant healthcare benefit to a wide population. The work will help prevention as well as progression into finding appropriate cures for hearing loss."
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 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.
"We now understand why hearing loss can be reversible in certain cases," says Hamann.
"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."