More than one billion people risk irreversible hearing loss from exposure to loud sounds such as music played on their smartphone, UN health experts have warned, unveiling new guidelines to help address the problem. The recommendations to prevent noise-induced hearing loss and related conditions such as tinnitus \u2013 commonly experienced as a ringing sound inside the ear - include better functions on personal audio devices that monitor how loud, and for how long, people listen to music. "Over a billion young people are at risk of hearing loss simply by doing what they really enjoy doing a lot, which is listening regularly to music through their headphones over their devices," said Technical Officer Shelly Chadha, who works on preventing deafness and hearing loss at the WHO. The one billion people at the risk of irreversible hearing loss are aged between 12 to 35 years. "At the moment, we don't really have anything solid other than our instinct to tell us: are we doing this right, or is this something that is going to lead to tinnitus and hearing loss a few years down the line?," she said. Today, hearing loss which is not addressed is estimated to cost the global economy USD 750 million, the World Health Organization (WHO) said. "Think of it like driving on a highway but without a speedometer in your car or a speed limit," Chadha said. "And what we have proposed is that your smartphone comes fitted with a speedometer, with a measurement system that tells you how much sound you're getting and tells you if you're going over the limit," she said. A parental volume control option is also included in the UN recommendations to industry, which participated in two years of discussions, along with experts from government, consumer bodies and civil society.