Generation after generation, teenagers have been told by their forebears to turn down that music. Now there seems to be a good medical reason to do so.

The World Health Organization warned in a recent report that over a billion young people are at risk for permanent hearing loss. One of the main culprits is a widely used device for listening to music — the smartphone. 

"Anything where you're putting sound into the eardrum, that's something as a society that we need to take a closer look at," says Rex Banks, chief audiologist at the Canadian Hearing Society.

That's because loud noises damage the cilia of the inner ear, the tiny hair-like structures that change sound waves into electrical signals that are carried to the brain. The damaged cilia never grow back. "Once they've been damaged, that's irreversible," says Banks.

Dr. Shelly Chadha, prevention of deafness and hearing loss technical officer for the World Health Organization, explains the danger with smartphones is that many people are listening to music that is simply too loud. 

Compounding the problem, says Banks, is the fact that people often listen to music when they are out on the street or in the subway where there is a lot of other background noise.


Ears ringing after a night at the clubs? That's your hearing trying to protect itself. (Yoshikazu Tsuno/AFP/Getty Images)

Most earphones that come with smartphones and MP3 players do a poor job of blocking ambient street noise. So in noisy urban environments, users frequently turn up the volume to maximum in order to overcome the din of city life. 

He points out that most of us are slowly damaging our hearing without realizing it.

But the ears have their own way of signalling danger. Coming out of a nightclub and finding that your ears are ringing or that you have to speak loudly to hear your own voice is a common situation that most people think is benign. But it is actually a defence mechanism your ears use to protect themselves from damaging noise levels, a phenomenon called a "temporary threshold shift."

Give your ears a rest

Banks says that when this happens you should get away from the noise give your ears a rest for about 12 hours. Hopefully, the damage hasn't become permanent and your hearing will recover.

There are ways to preserve your hearing.

A normal speaking voice usually measures around 60 decibels. Volumes above 85 decibels will cause damage after about eight hours and levels above 100 decibels can do so in 15 minutes. But measuring decibel levels is impractical and complicated for most people. 

Chadha recommends an easier test. 

Sit in a quiet room and listen to your music at about 50 to 60 per cent of the maximum sound level of the device. You should still be able to carry on a conversation with a person sitting near you. If you can't hear that person, the music is too loud.

Banks recommends holding your ear buds and closing your fist around them. If you can hear the music through your fist, you're playing it too loud.

Some solutions

One solution to the problem could be noise-cancelling earphones that can block ambient sound and allow music lovers to listen to their music at lower and safer volumes.

There are also built-in safety options for most devices. Apple introduced a way of limiting the volume on its iPod and iPhone devices after a 2006 class action lawsuit accused it of not taking adequate measures to protect its customers' hearing. Google has introduced similar volume-limiting apps for its Android devices.

But Banks warns that none of these features is perfect and nothing should give you licence to expose yourself to as much noise as you want. 

He says the best strategy is to remove, reduce and rest: Remove yourself from prolonged loud sounds, reduce the amount of background noise around you and give your ears a chance to rest and recover.​

Chadha says the goal of the WHO report was not to scare people from using smartphones. She says that if you listen to your music at safe volumes, you can listen for long periods. 

"We're not telling people not to listen to music, just to make sure that they listen safely forever."

Christopher Labos is a cardiologist and epidemiologist at the McGill University Health Centre. He is currently a fellow in global journalism at the Munk School of Global Affairs at the University of Toronto.