Teenagers cranking up the music on headphones and other personal devices are being warned that they risk losing their hearing if they do not change their habits urgently.
Results from a new survey carried out by the National Foundation for Deaf & Hard of Hearing found many young people had the volume settings up far too loudly.
As a result, their hearing suffered - with 34 per cent of the 479 Year 9 students found to have "abnormal hearing", meaning that their parents were advised to get them checked by their family doctor.
That's much higher than a World Health Organisation (WHO) estimate that 20 per cent of people aged between 12 and 35 suffer from hearing loss - and that global figure was up by a third since the late 1990s.
Students from Auckland's Rutherford College and Manurewa High took part in the Listen Up Screening Pilot programme; as did students from Picton's Queen Charlotte College.
The results varied wildly, with 42 per cent of students found to have abnormal hearing at Rutherford (decile 5), 32 per cent at Manurewa (decile 1) and only 10 per cent at Queen Charlotte (decile 6).
More than a third of all those tested said they experienced ringing in their ears, which was possibly a precursor to tinnitus - 41 per cent of those with abnormal hearing and 36 per cent of those with "normal" hearing.
At Manurewa, 28 per cent of students tested said they listened to music at maximum volume for more than three hours a day.
WHO recommends youths are not exposed to maximum levels for more than six minutes a week.
Foundation for the Deaf chief executive Natasha Gallardo said most students were using either headphones or ear buds to listen to their devices.
"This really is becoming a public health issue, and as a nation we need to address youth hearing loss immediately," she said.
"Once you lose your hearing, you cannot get it back. Yet the propensity for teenagers to put their hearing at risk is truly frightening. Parents, caregivers, teachers, employers – we all have to take urgent steps to help young people see the harm they might be doing."
The foundation plans to lobby the Government for mandatory hearing screening of high school pupils, as currently there are no compulsory checks after pre-school monitoring.
"We need a national programme to assess just how extreme youth hearing loss rates are, and identify children that are at risk early, as prevention and early detection are key," Gallardo said.
WHO says acceptable daily sound levels work like a monetary allowance: you have a limited amount to spend each day. The louder or longer you are exposed to high levels of sound, the more you "spend", the faster you run out of your allowance.
Safe listening levels depend on the intensity (loudness), duration (length of time) and frequency (how often) of the exposure. The highest safe sound level is 75 decibels up to a maximum of eight hours. So you could be exposed to the same level of loudness in 15 minutes of music at 100 dB as an industrial worker gets in an eight-hour day at 85 dB.
How to spot someone with hearing loss
• They turn the TV volume up louder than you would.
• They miss parts of the conversation, and ask you to repeat it.
• They lean forward with an ear towards the sound."