Specialists say we are sitting on a hearing-loss timebomb, and predict a surge in problems in 10 to 20 years.

Hong Kong College of Otorhinolaryngology fellow Albert Luk Wai- sing said: "The full fallout from prolonged and intense MP3 use is not yet known, but we will see a significant rise in the number of premature hearing-loss cases among youth entering their middle age a decade or two from now."

Speaking at the Hear Talk Foundation Ear Caring Day ceremony at Tsim Sha Tsui's Kowloon Park Piazza yesterday, Luk warned that more than half of secondary school students are not taking steps to protect their hearing. Luk said people are assaulted by urban noise pollution daily, but using loud music to drown it out could lead to irreparable damage.

With roadside traffic at 70 decibels, an MTR ride at 80 and construction noise at 90, people wearing conventional earphones have to crank their music up to over 100 decibels to drown out the racket, well beyond a healthy tolerance of 80, Luk said.

According to an ongoing survey on the auditory health of Hong Kong's secondary school population, less than a quarter of about 4,000 respondents use silicon or noise-canceling earphones capable of shielding external noise. Given the 83 percent MP3 use rate among the students surveyed, the problem is only going to get bigger. Last year 1.67 million MP3 devices were sold, compared with 740,000 in 2003 and 370,000 in 1998, Luk said.

Hearing-loss symptoms emerge around the age of 25, Luk said, emphasizing that teenagers should take steps today to protect their hearing. According to the foundation, of the 34.2 percent of seniors suffering from hearing loss, one-fifth also suffer depression, twice the number of elderly with normal hearing.

Ear, nose and throat specialist Peter Tang Shu-on said the onset of tinnitus - a ringing in the ears or a high-pitch buzz after moving from a loud to quiet area - are symptoms of hearing damage.

He said people experiencing phantom noises should leave loud areas immediately or risk permanent damage.

A recent survey by the foundation of five secondary schools found 70 percent of respondents regularly set their music volume to maximum to override ambient noise. Experts suggest users limit themselves to 60 percent volume capacity for a maximum of 60 minutes at a time.

But the warnings seem be falling on deaf ears: this year's survey found 23 percent plugged in 20 hours or more a week, while 15 percent of that group were wired for music for over 50 hours a week.