Noise induced hearing loss: What's that?

Of the 40 million people with hearing loss in the U.S., 25 percent of those, or 10 million, have lost their hearing as a result of exposure to excessive noise. But how much noise is too much?

Measured as decibels (dB), the acceptable manufacturing noise standard is to allow a daily exposure up to but not over 85 dB in an eight-hour period. More than that can cause permanent injury to our hearing. This is likely due to wear and tear on the tiny hairs that vibrate when sound is introduced. It’s like a line of kids walking across one path on the grass day after day. A little is good, too much kills the grass.

The average conversation, for example, is usually around 50-60 dB, street noises at 70-80, and an operating lawnmower at about 90. Noise levels above 90 come from surprising places like screaming babies, convertibles driving at 60 mph, marching bands, leaf blowers, hand and hair driers, and those noisy electronically amplified concerts. Single loud sounds like gunfire at about 150 dB can also be damaging, but the time exposed to lower volumes are the most significant and unrecognized danger we face daily.

A recent social trend has created a new threat. Tuning out the world with ear buds, while turning up the tunes for hours, can be like riding on the two-cylinder John Deere tractor with no cab all day while cultivating corn. Those old two-cylinders were loud, and so it can be with ear buds! Ear bud volumes at 100 dB for as short as 15 minutes can damage hearing. Again, it’s the volume multiplied by time that makes it so bad. One study showed that 97 percent of third graders had documented exposure to hazardous sound levels. Another showed that 12.5 percent of 6 to 19-year-olds in the U.S. already had hearing loss directly attributed to noise exposure.

What’s more, if the volume is too loud, ear buds can be even more unsafe as they may prevent us from hearing the noises that help us avoid danger. For example, walkers, runners, and bicyclists need their ears to hear when a truck might be coming from behind.

Of course, it isn’t just noise that can reduce our hearing. Infections, trauma, and even medications like antibiotics, chemotherapy drugs, or pain medications can do it too. Seek medical help if you notice your hearing is changing.