Noise Induced Hearing Loss

By Richard P. Holm, MD

Of the 40 million people with hearing loss in the United States, 25% of those, or 10 million, have lost part or all of their hearing as a result of excessive exposure to too much 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 of time. More than that can cause permanent injury to our hearing. This is likely due to wear and tear on the tiny cells in the ear, called hair cells, that vibrate when sound is introduced. It’s like a daily line of college kids walking too often across one path on the grass. A little is fine; too much kills the grass.

The average conversation, for example, is usually around 50-60 dB, street noises at 70-80 dB, and an operating lawnmower at about 90 dB. Single loud sounds like gunfire at about 150 dB can also be damaging, but realize that the time exposed to lower volumes are the unrecognized danger we face daily. Noise levels above 90 dB 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. 

Now a new threat has turned up. Tuning out the world with ear buds, while turning up the tunes for hours, can be like riding on a 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 the time of exposure that makes it so bad. One study showed that 97% of third graders had documented exposure to hazardous sound levels, while another showed that 12.5% of 6-19 year olds in the U.S. already had hearing loss directly attributed to noise exposure.

What’s more, ear buds can be even more dangerous if the volume is too high and blocking out the ambient outside noise, which is needed to 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, and we need to be aware. But the take home message for today is to protect ears by avoiding exposure to too much noise, and that the noise from ear buds is a new and dangerous threat.