People should listen to music for no more than one hour a day to protect their hearing, the World Health Organization suggests.
It says 1.1 billion teenagers and young adults are at risk of permanently damaging their hearing by listening to "too much, too loudly".
It said audio players, concerts and bars were posing a "serious threat".
WHO figures show 43 million people aged 12-35 have hearing loss and the prevalence is increasing.
In that age group, the WHO said, half of people in rich and middle-income countries were exposed to unsafe sound levels from personal audio devices.
Meanwhile 40% were exposed to damaging levels of sound from clubs and bars.
The proportion of US teenagers with hearing loss went from 3.5% in 1994 to 5.3% in 2006.
Dr Etienne Krug, the WHO's director for injury prevention, told the BBC: "What we're trying to do is raise awareness of an issue that is not talked about enough, but has the potential to do a lot of damage that can be easily prevented."
The full report argued: "While it is important to keep the volume down, limiting the use of personal audio devices to less than one hour a day would do much to reduce noise exposure."
Dr Krug said that a good ambition aim.
"That's a rough recommendation, it is not by the minute, to give an idea to those spending 10 hours a day listening to an mp3-player.
"But even an hour can be too much if the volume is too loud."
The WHO's safe listening times are:
- 85 dB - the level of noise inside a car - eight hours
- 90 dB - lawn mower - two hours 30 minutes
- 95 dB - an average motorcycle - 47 minutes
- 100 dB - car horn or underground train - 15 minutes
- 105 dB - mp3 player at maximum volume - four minutes
- 115 dB - loud rock concert - 28 seconds
- 120 dB - vuvuzela or sirens - nine seconds