When the University of Utah's football team scores a touchdown, the roar of the crowd is as loud as an F-16 flying overhead. The fireworks display at the park produces, at times, the equivalent of a gunshot. And 15 minutes at a rock concert — or using a leaf blower — can reduce hearing permanently, although it may be too slight to notice it at first.

It's called noise-induced hearing loss. And it seems to be built into the American lifestyle.

"People just abuse their ears," said University of Utah physics professor Orest Symko, who teaches the physics of audio and video. "I have a feeling people all will eventually become deaf. . . . It's called evolution."

So-called age-related hearing loss may, in fact, be noise induced. Aboriginal tribes and folks in quiet areas don't lose any hearing over time.

Certain hearing loss is largely preventable, experts agree.

Recently, the Deseret Morning News and KSL-TV took "readings" of sound levels at popular entertainment venues, using equipment and expertise provided by the Rocky Mountain Center for Occupational & Environmental Health. We found many exceeded the 85 decibel threshold where prolonged exposure can cause damage.

• A popular Salt Lake-area public fireworks display on the Fourth of July averaged 87 decibels (dB) over time and peaked for a split second at 136 dB, a level OSHA forbids in the workplace without hearing protection.

• The movies "Cars," "The Fast and the Furious: Tokyo Drift" and "Poseidon" ranged from about 77 dB to 80 dB over time, with "Poseidon" hitting a split-second peak of 114.3 dB — about as loud as a rock concert.

• A boat that seemed quiet maxed at 95 dB while pulling a skier.

• A 3006 hunting rifle peaked at 144.6 dB — more than 10 times louder than what's called the pain threshold.

• Utah-legal fireworks lit at home maxed at 101.6 dB, and for a split-second, 133.8 dB. Experts say illegal fireworks are louder.

Minimal exposure to movies, fireworks and boating probably isn't going to hurt you. But doing these types of activities — and many other ordinary tasks — often, or for long periods of time, could. And for some, a single gunshot blast can do damage. It's just hard to say who is susceptible until it happens.

You have to understand hearing, the process that converts sound waves into electrical signals the brain translates as sound, to understand how it gets broken.

The eardrum and the three tiny bones in the middle ear amplify vibrations and carry them to the inner ear, where the bone nicknamed the stirrup sends them through a little opening into the fluid that fills the inner ear. The vibrations pass through that fluid in the cochlea, moving the tops of the hair cells located there, called a hair bundle, and sparking nerve impulses. Different sounds move the hair bundles in different ways, allowing the brain to distinguish between them.