The evidence is undisputed. What you don’t know can damage your hearing for life. Noise-induced hearing loss is probably the biggest global public health emergency you’ve never heard of. The World Health Organization says one of every five U.S. teens (ages 12–19) has a measurable hearing loss likely from loud noise.

The WHO calls hearing loss a global health crisis with 1.1 billion young people at risk from damaging sound, largely from personal listening devices turned up too loud.

Protect yourself from hearing loss. Experts give this advice: Turn down the volume on personal listening devices to 60% of volume or lower. Take a listening break every hour. Use earplugs in noisy places or situations such as sports stadiums or in the presence of heavy machinery or loud music.

Untreated hearing loss has serious health consequences: It can harm the heart and brain; lead to mental health problems like depression; and cause sleeping problems and even cognitive decline. Untreated hearing loss impacts school and job performance, and income.

Hearing loss can result from a one-time exposure to loud sound — up close at a concert — or from loud noise over prolonged periods.

Be aware of the noise level around you and protect yourself using earplugs or by moving away from the noise, urges the National Institute on Deafness and Other Communication Disorders.

Damage to hearing is cumulative, says the NIDCD. The louder the noise and the longer the exposure, the greater the risk of permanent damage.

Over-the-ear or noise-canceling headphones that block out the sound around you make them a better choice than in-ear earphones or earbuds. Without competing outside noise, you’re less likely to turn up the volume to unsafe levels — just make sure you remain aware of your surroundings.

The CDC considers sound at 70 decibels and below to be safe. Some headphones can top out at 100 decibels or more, which can permanently damage hearing in just 15 minutes. People regularly experience dangerous decibels — in restaurants and bars, on subways and at the gym.

Hearing loss is usually subtle, occurring gradually; most people may not be aware they are affected.

Often those close to us spot the problem first. It’s a good idea to check your hearing from time to time. Online hearing tests (such as the WHO’s hearWHO app) are quick and easy and can alert you to a problem.

Editor's note: Timothy Higdon is president and CEO of Hearing Health Foundation. Visit hhf.org/keeplistening.