The lowly earplug, generally a cheap piece of spongy foam, is starting to gain attention as a safety device — akin to seat belts, sunscreen and bike helmets — that can protect ears from the damage caused by the loud noises of everyday life.

What noises?

Not just concerts and football games, where people often leave with clear signs of harm, such as muffled hearing and ringing ears.

Damage from noise that doesn’t seem all that bad in the moment — such as the music in spinning class and the buzz of a lawn mower — can accumulate slowly, harming hearing in ways that may not reveal themselves for years.

Enter the ounce of prevention: the earplug. They’re cheap, available, easy to tote in purse or pocket and woefully underused, hearing specialists say. The greatest risk from noise, hearing loss, is often unnoticed in its early stages. Tinnitus, an insistent and often distressing ringing or buzzing, is easier to recognize.

Justin Bieber may not realize that foam earplugs shouldn’t obviously stick out of the ear. (Jeff Kravitz/FilmMagic)

Even more rare and debilitating is hyperacusis, a sound sensitivity where everyday noises such as clinking ice cubes seem loud and painful. Hyperacusis can progress to constant, burning ear pain. “People can’t comprehend your normal-looking outward appearance with the unseen disturbance going on inside your head,” said Richard Salvi, a professor at the University at Buffalo in New York and scientific advisor to the nonprofit Hyperacusis Research.

Like many people, Gifford Krivak, a Fairfax County high school English teacher, never thought about shielding his ears from noise. As a track coach, he used a starter’s pistol, but the resulting ringing in his ears always resolved quickly.

Last year, after a flight from Baltimore to Houston, he felt intense ear pressure while descending. The ringing returned, this time for good. “I never heard of tinnitus until I had to deal with it,” he said. “And no doctor had ever mentioned it.”

Krivak, 48, has the trifecta, with some hearing loss and mild hyperacusis, too. Noise makes his ears hurt. “I have had to leave a baseball game in the sixth inning,” he said. Despite ear protection, “it was just too loud.”

Now, to prevent worsening, he always has earplugs at the ready. He wears them on the Metro, during fire drills and whenever noise is unavoidable.

“Learning how to put them in correctly was an issue,” he said. “It took me a while to figure it out.”

Foam earplugs — the cheapest, most common and most protective — must be rolled between your fingers into a tight cylinder and then inserted into the ear where they expand to fill the ear canal. The key is the insertion: People need to pull the ear up, out or back to help the earplug slip beyond the curve in the ear canal.

“It’s a very individual thing,” said Theresa Y. Schulz, hearing conservation manager for Honeywell Safety Products, which makes protective hearing devices including earplugs. “Everybody’s ear canal is different.” People worry the earplug might hit the eardrum and cause pain or damage, but “you are not anywhere near the eardrum.”

If inserted correctly, foam earplugs shouldn’t obviously stick out of the ear. They should be invisible, or nearly so, from the front. At the recent MTV European Music Awards, Justin Bieber demonstrated how not to wear an earplug. The protection afforded by an earplug sticking far out is little to none. The National Guard’s tip for its members: Do jumping jacks; if an earplug falls out, it wasn’t in properly.

Earplugs come in many varieties, all of which have pros and cons. Beyond the squishable foam kind, there are moldable silicone ones — a kind of putty — that pancake over the ear opening, covering it and sticking in place. (Unlike the foam kind, they don’t extend far into the ear canal.) Flange earplugs, which look like baby pine trees, in some cases soften with body heat, helping with the comfort factor. They’re inserted into the ear canal, like foam ones.

For the average user, there is no best earplug. Experts encourage people to experiment with different types to find the most comfortable ones and to practice using them. Instructional videos can be found online.

Also good to know: Earplugs should be removed slowly — not yanked out — to avoid an uncomfortable plunger, or suction, effect. For babies and small children, noise-blocking earmuffs are easiest to take on and off. (Besides, earplugs are a choking hazard.)

As for when to use protection, experts say that when the ambient noise would drown out the voice of someone sitting next to you, you should use earplugs and save the conversation for later.

In a pinch, Schulz suggests sticking your fingers in your ears if you’re suddenly or unexpectedly exposed to loud noise — a siren going by or fireworks going off.

For those whose ears have already been damaged, earplugs may not be enough.

“I will not go to concerts anymore,” Krivak said. “I really don’t care who’s playing.”

Cohen is a writer who lives in New York.