Many factors can cause hearing loss, including the degeneration of organs with increasing age, damage to nerves and blood vessels by toxins, diseases and injuries.

While age is the single biggest cause of hearing impairment, the modern urban lifestyle can contribute to age-related hearing loss, with direct damage to the ear, experts say.

"About 15 years ago, I had few patients complaining of hearing loss in a whole year," says Chen Chongxue, an ear, nose and throat specialist with No 1 Hospital of Tsinghua University in Beijing.