MP3 players and iPods sold in the EU will soon be required to have a default setting to discourage people from listening at dangerously high volumes.

The EU is revising its safety standards for personal music players after a scientific committee warned that prolonged exposure to loud playback on these portable audio devices could permanently damage hearing.

The commission asked the committee for its opinion in light of the growing popularity of portable music players, including mobile phones, especially among the young.

Sales of these devices have soared in recent years. In the EU, between 50 and 100 million people use them every day. It is estimated that as many as 10 million of these are at risking problems with their hearing in later life.

So how loud is too loud? The answer depends on how long you listen.

There are essentially two problems with personal music players. For starters, people often use them in noisy places – on the bus for example – and so have to turn up the volume. With some devices, the volume even goes up automatically.

The other problem is prolonged use. A lower volume may be more harmful than louder music if the exposure is longer.

With most personal music players, the sound level ranges from 60 dBA (decibels adjusted) to 120 dBA. According to the scientists, hearing loss is not likely to occur at levels below 80 dBA – roughly the equivalent of someone shouting or traffic noise from a nearby road. Even at 80 dB(A) you can still listen safely up to 40 hours a week. But turn up the sound a bit, and the risk goes way up. At 89 dB(A), five hours per week is the recommended maximum.

Besides providing a default setting, personal music players will have to alert consumers to the risk of overriding the safety limit. This could be a label or an on-screen warning – the technical details will be up to manufacturers.

Currently producers are only required to include a warning in the instruction manual.