THE HUMAN RACE IS LOSING ITS HEARING

Prolonged exposure to loud noise — usually from portable devices played through earphones — is the culprit, writes Guy Kelly

If Nicole Russell could turn back the clock, she’d turn down the volume. In 2004, at seven years old, Russell picked up an Apple iPod, plugged in a pair of the standard white headphones, pressed play, cranked it up, and formed a habit she’d enjoy for “at least five hours a day” for the next decade. She’d listen in the morning, on the way to school, during break, even as she fell asleep.

She used headphones with her iPad, and when she watched television, she’d turn the volume up high. While she was at university, doctors diagnosed her with hearing loss in both ears and said there could only be one cause: the excessive loud music.

In our increasingly noisy society, stories like Russell’s are common. A report by the World Health Organisation says that nearly 50% of people aged between 12 and 35 — or 1.1-billion young people — are at risk of hearing loss “due to prolonged and excessive exposure to loud sounds, including music they listen to through personal audio devices”.

“People don’t know about safe listening levels, and in a culture where headphones are everywhere, that’s dangerous,” says Francesca Oliver, an audiology specialist at Action on Hearing Loss in the UK.

“Biologically, our ears have not adapted to withstand the volume of noise most of us encounter — or subject ourselves to — almost every day.

“For example, anyone using headphones should listen at less than half the maximum volume for no more than half an hour at a time, but how many people know that or implement it?”

It’s believed that everybody — from obvious cases like musicians and construction workers, to the rest of the public (commuters, gym-goers, school children, hairdressers, drivers, toddlers, or anyone with a handheld device) — is in danger of damaging their hearing from overexposure to loud noises, more than ever before. Put plainly: the human race is losing its hearing.

To understand what noise-induced hearing loss is, it helps to understand the ears.

The outer, cartilaginous part — the pinna — is unique to us: the shape, protrusion, size are all matched with your height, head shape, everything that makes you “you”. Swap ears with your partner and you won’t be able to hear properly.

Inside the ear are two muscles and three of the smallest bones in the body. When sound waves hit the eardrum, vibrations move through these bones to the inner ear, the cochlea, where they meet 15,500 tiny hair cells, called stereocilia, divided into 3,500 inner hair cells and about 12,000 outer hair cells.

When sound arrives, these move, sending signals along the auditory nerve to the brain, which interprets what the sound is and where it’s coming from. These hair cells are crucial to what makes hearing loss so dangerous. They’re in limited supply. At 10 weeks of foetal gestation, all 15,500 are created, and from that point on, for the rest of our lives, we can only ever lose them.

Picture a perfect, luscious lawn of grass — each blade erect. This represents your hair cells at birth. Ideally, all the grass has to handle is wind, rain and the occasional bird plodding over it. This is safe, low-level sound, like people talking or music played at a reasonable volume.

Now imagine if someone walked or drove across that grass. That’s like exposure to very loud noise. This is the feeling of your ears ringing after a party, before the sensation wears off by the next morning.

But if you keep cutting across the lawn on that same path over days, weeks, months and years, the grass will wear down to such a damaged state that it cannot recover. This is what happens with hearing loss: hair cells have been destroyed permanently, creating a gap, so sound waves have no way of getting to the brain. And it’s irreversible.

The “safe sound threshold” sits at around 80-85 decibels (dB) — somewhere between a vacuum cleaner and an alarm clock. After eight hours’ exposure at 85dB, hearing is damaged.

The scale is then exponential: each increment of 3dB doubles the pressure, therefore halving the safe exposure time. An iPod at full blast is about 100dB, the same as a nightclub or hairdryer. Just 15 minutes of that can result in hearing loss.

Moving up the scale, a rock concert is about 113dB. A pneumatic drill is harmful after one second. A gun blast is even quicker.

Sound is a force that can destroy more than ear hair cells. When a bomb levels a house, it’s sound that’s tearing those bricks apart. The simplest thing we can do is be aware of the noise levels of the environment we’re in, then act. There are free apps that act as sound meters (Apple introduced a similar feature on its watches last year), which instantly tell you the decibel level you’re experiencing. If you can control the level, turn it down. If you can’t, specialist ear plugs are cheap and easy to carry around.

The message to save our ears is loud and clear – but is anybody listening?