Have you ever found it difficult to hear friends or family while engaging in a space filled with background noise? You may be suffering from a medical condition called hidden hearing loss.

Potentially impacting millions of people, especially those living in noisy, urban environments, hidden hearing loss is a phenomenon that can happen in those who otherwise have good hearing. In fact, standard hearing tests won't detect it.

“We live in a really loud world,” said Barbara Shinn-Cunningham, a professor of biomedical engineering in Boston University’s College of Engineering who studies hidden hearing loss. “We can’t really test how much noise exposure people have had over a lifetime. But when we do these tests, we ask subjects questions such as: Do you mow the lawn a lot? Do you like loud music? And the people with the most noise exposure tend to be the worst listeners.”

How it works

So why can you hear in a doctor's office just fine but not in a crowded bar with friends? In a healthy ear, sound waves are picked up by hair cells and processed into signals that can be interpreted by the brain. As we age or are exposed to extremely loud noises, these hair cells can be damaged and die, causing what's known as standard hearing loss.

In an ear with hidden hearing loss, the synapses that relay the signals from hair cells become damaged. Lose enough of them and the ear's ability to filter out background noise and focus on important conversations becomes limited.

"It’s as if there’s a big Jumbotron showing a picture," Harvard researcher M. Charles Liberman told CBS News, "but as more and more of its bulbs go black, it gets harder and harder to realize what the picture shows."

While standard tests gauge hearing sensitivity using auditory tones, a new hidden hearing loss exercise asks you to repeat phrases against louder static background noise. The test — which was prepared for the Associated Press by the Mailman Center for Child Development at the University of Miami — will reportedly give those with hearing loss trouble by the second or third track.

While there is currently no treatment for hidden hearing loss, researchers like Liberman are making advancements in the development of a drug that may be able to regrow damaged synapses.

The best advice for those looking to avoid further loss is to limit exposure to loud environments, wear ear protection when using machinery, and simply turn down the music.

Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.