MP3 Players: How Loud Is Too Loud? Acoustic Study Shows Safe Listening Levels

June 1, 2007 — Loud, sustained sound can damage tiny hairs in the cochlea, and yet 80 percent of people listen to personal music devices at dangerous levels above background noise, a study by acousticians shows. Certain models of earphones are safer for the ear, the study also concluded.

Can you hear me now? Not if you've pumped up the volume on your MP3 player. In noisy places, everyone is turning up the tunes, and they could be drowning out their own hearing. A new study tells how loud is too loud.

Audiologists Brian Fligor, Sc.D., and Terri Ives have identified safe volume levels for you to use in noisy places. Dr. Fligor, an audiologist and Director of Diagnostic Audiology at Children's Hospital Boston says, "Your typical listener is not at risk if they are listening in a quiet situation, but if they are in a noisier situation, such as commuting, they very easily are going to be at risk." Their study concludes that 80 percent of people listen at dangerous levels when background noise comes into play.

As sound travels through the ear canal, it ends up in the inner ear, or cochlea. When it's too loud, tiny hair cells, which send sound information to the brain, are damaged or destroyed. "They're not meant to be hit with noise for long periods of time," Dr. Fligor says. Over time, this can lead to permanent damage of the hair cells and your hearing.

The study concludes the average person listens to music at the same noise level as we hear a gas lawnmower. So what can you do? Dr. Fligor says, "Something that people can do is set their music to a comfortable level when they are in a quiet situation." Dr. Fligor recommends leaving it at that safe level, 75 decibels or below, and investing in earphones that block out background noise.

During the study, only twenty percent of patients who used "in-the-ear" earphones, designed to block out background noise, exceeded sound levels considered to be risky, compared to 80 percent who listen dangerously with other types of earphones. Proof that your choice of earphone combined with smart volume control settings can help save your hearing. Turning down the music will ensure you will be able to hear music in the future.

BACKGROUND: As portable digital music players -- iPods and other MP3 players -- become more and more popular, people are becoming concerned about whether they are dangerous to our hearing. Now hearing researchers have measured specific sound levels in a variety of players using several different types of earphones. They used this information to develop the first detailed guidelines with safe volume levels for listening to the iPod with earphones. They also evaluated the output levels of several other popular players to determine any risks to hearing from using these devices.

ABOUT HEARING LOSS: Loud sounds stress and could damage the delicate hair cells in the inner ear that convert mechanical vibrations in the air (sound) into the electrical signals that the brain interprets as sound. If exposed to loud noises for a long time, the hair cells can become permanently damaged and no longer work, producing hearing loss. Noise-induced hearing loss can be caused by two types of noise: sudden bursts, such as firearms or fireworks; or continuous exposure to loud noise, such as motorized recreational vehicles, loud sporting events, power tools, farming equipment, or amplified music. For a person to lose their hearing because of continuous exposure, it would depend on how loud the sound was and how often and for how long they heard it. It takes repeated exposures over many years to cause a noise-induced hearing loss in both children and adults.

WHAT THEY FOUND: The researchers conducted a study observing the listening habits of 100 graduate students listening to iPods through earphones. They found that all the players had very similar sound output levels. Also, in-ear earphones, which broadcast sound directly into the ears, are no more dangerous than headphones placed over the ears. However, if the user listens to music in noisy surroundings, they are much more likely to raise the volume to risky levels, suggesting that people should seek quieter listening areas when possible, and use earphones that block out background noise.

RECOMMENDED LEVELS: The more often and the louder you player your player, the more likely you'll experience some hearing loss. To come up with recommended listening times and sound levels, the researchers compared the players' volume levels to the minimum sound level for the risk of hearing damage: 85 dBA. Typically, a person can tolerate about two hours of 91 dBA per day before risking hearing loss. The researchers recommend listening to iPods for -- hours a day with earphones if the volume is at 80% of maximum levels. Listening at full volume is not recommended for more than 5 minutes per day using the earphones that come with the player.

The Acoustical Society of America contributed to the information contained in the video portion of this report.

Editor's Note: This article is not intended to provide medical advice, diagnosis or treatment.

Note: This story and accompanying video were originally produced for the American Institute of Physics series Discoveries and Breakthroughs in Science by Ivanhoe Broadcast News and are protected by copyright law. All rights reserved.