31st August 2012 - It is well known that loud music can damage hearing, now a study by the University of Leicester has uncovered just how the damage is caused.
Nerve cells carrying electrical signals from the ears to the brain have a protective coating called the myelin sheath. Pumping up the volume and exposing ears to loud noise over 110 decibels can strip the cells of the coating. This disrupts the signals, causing hearing problems over time.
Action on Hearing Loss says some portable music players can be wound up to volumes of 100dB(A) - above danger levels and as loud as being next to a pneumatic drill at road works.
Dr Martine Hamann from the University of Leicester department of cell physiology and pharmacology led the hearing loss study. "Dissecting the cellular mechanisms underlying this condition is likely to bring a very significant healthcare benefit to a wide population," she says in a news release. "The work will help prevention as well as progression into finding appropriate cures for hearing loss."
Dr Hamann says the sheath can rebuild itself allowing the nerve cells to work properly again, meaning hearing loss can be temporary. "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."
Earlier research by the Leicester team focussed on the effect of loud noise on the brain's dorsal cochlear nucleus. This carries signals from the ear's nerve cells the part of brain responsible for decoding and understanding sound.
Damage to cells in this area was found to cause tinnitus, or ringing in the ears.
Reacting to the findings in an emailed statement Action on Hearing Loss's head of biomedical research Dr Ralph Holme says: "Tinnitus erodes the quality of life for more than 600,000 people in the UK, which is why it is so important that effective treatments are developed to silence it.
"Only with more investment in research, like that being carried out at the University of Leicester, to better understand the cellular processes involved can we hope to find much needed cures."
Tips to protect hearing
Action on Hearing Loss offers tips on protecting hearing for people using personal music players.
It says good quality earphones or headphones are important. Some of the ones that come free with a gadget may be poor quality, leaking sound and letting in the background noise. To get round this, people simply turn up the volume, sometimes to dangerous levels.
The charity says sound-isolating or noise-cancelling headphones are better at blocking background noise, so listening volumes can be lower.
It also recommends regular breaks from music through earphones of at least five minutes an hour.
Many devices have volume limiting features which can be used to set safe maximum volume levels.
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