When does the use of headphones become harmful?

Question

Generally, it is known if you listen to music through headphones a lot of time, you damage your ears.

But how long should I use the headphones? And how loud can they be so as not to affect my hearing?

Answer 1

Using headphones at a sufficiently high volume level may cause cause trauma to cochlear structure in the inner ear which gives rise to temporary or permanent hearing impairment or deafness.

Sound pressure is measured in decibels and exposure to 75dB (even after long exposure) are usually safe. However, long or repeated to sounds at above 85dB can cause hearing loss. The louder the sound, the shorter the amount of time it takes for NIHL to happen.

The risk is higher especially in loud places as volume often needs to compete with the background noise. For example, the average sound level on a busy street is about 80dB. In the Airo study, when the outdoor noise was a mere 65dB, listeners raised headphone volume levels to over 80dB¹⁹⁹⁷.

This figure shows the average chosen listening levels for our subjects across the different background noise levels²⁰⁰⁶:

When we experience sound in our environment (TV, radio, traffic), normally these sounds are at safe levels, however long period of exposure to high sound pressure levels at high volume can be damaging to sensitive structures in the inner ear and cause noise-induced hearing loss (NIHL).

The anatomy of hearing loss (simplified view):

Image credits: HeadWise

Hearing damage from headphones is probably more common than from loudspeakers, even at comparable volumes, due to the close coupling of the transducers to the ears.

Symptoms of hearing damage:

• Ringing or buzzing in the ears.
• Difficulty in understanding speech.
• Slight muffling of sounds.
• Difficulty understanding speech in noisy places or places with poor acoustics.

Recommendations

The WHO recommends that young people limit the use of personal audio player to one hour a day in an effort to limit exposure to noise.

NIOSH recommends a safe headphone listening volume of 85dB. Although headphones are not sold with SPL meters, they can be purchased separately.

One could note of the volume control setting that pumps out 85dB, any music recorded at a higher level would still play back at dangerous levels. The headphones would have to be recalibrated whenever the music changed.

While in-the-ear earphones can produce higher sound levels than over-the-ear earphones, they are not necessarily used at higher levels.

The table above shows NIOSH recommended maximum listening time per day, depending on the style of earphones used and the volume control settings on the player. On this chart, the “Isolator” style refers to earphones that have been reported to block out background noise, and “Supra-Aural” style refers to earphones that sit on top of the ear. The final column shows our measurements for the iPod, using the stock earbuds from Apple.

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Here are the average decibel ratings of some familiar sounds:

• 45dB

  • The humming of a refrigerator.

• 60dB

  • Normal everyday conversation.
  • Ringing telephone.
  • Normal piano practice.

• 70dB

  • Restaurant.

• 80-85dB

  • Heavy city traffic, alarm clock at 2 feet, factory noise, vacuum cleaner, garbage disposal.

• 90-95dB

  • Motorcyles.
  • Subway trains, motorcycle, workshop tools, lawn mower.

• 100-110dB

  • An MP3 player at maximum volume.
  • Dance club.
  • Chain saw, pneumatic drill.
  • Timpani & bass drum rolls.

• 120dB

  • Sirens.
  • Symphonic music peak. Rock concert speaker sound, sandblasting, thunderclap.

• 130dB

  • Jet take off.
  • Gunfire.

• 150dB

  • Firecrackers and firearms.
  • Rock music peak.

The distance from the source of the sound and period of time are also important factors in protecting your hearing.

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Read also:

• 1.1 billion people at risk of hearing loss - WHO highlights serious threat posed by exposure to recreational noise

  Data from studies in middle- and high-income countries analysed by WHO indicate that among teenagers and young adults aged 12-35 years, nearly 50% are exposed to unsafe levels of sound from the use of personal audio devices and around 40% are exposed to potentially damaging levels of sound at entertainment venues. Unsafe levels of sounds can be, for example, exposure to in excess of 85 decibels (dB) for eight hours or 100 dB for 15 minutes.

  Teenagers and young people can better protect their hearing by keeping the volume down on personal audio devices, wearing earplugs when visiting noisy venues, and using carefully fitted, and, if possible, noise-cancelling earphones/headphones. They can also limit the time spent engaged in noisy activities by taking short listening breaks and restricting the daily use of personal audio devices to less than one hour. With the help of smartphone apps, they can monitor safe listening levels

• Causes of Hearing Loss in Adults at ASHA

  Very loud noise can cause permanent hearing loss. This is called noise-induced hearing loss. Listening to loud noise for long periods of time can damage the hair cells in the inner ear. Noise-induced hearing loss usually develops gradually and painlessly. A single exposure to an extremely loud sound such as an explosion can cause a sudden loss of hearing. This is called acoustic trauma.

• Noise-Induced Hearing Loss at NIDCD

• Preventing Hearing Damage When Listening With Headphones (DOC) at HeadWise
• Hearing Loss Web site
• (PDF) "Does earphone type affect risk for recreational noise-induced hearing loss?" Brian J. Fligor, Sc.D., CCC-A and Terri Ives, Sc.D, 2006
• "Sound Output Levels of the iPod and Other MP3 Players: Is There Potential Risk to Hearing?" Cory D. F. Portnuff and Brian J. Fligor, Sc.D., CCC-A, 2006

• Occupational noise exposure at OSHA

  When the daily noise exposure is composed of two or more periods of noise exposure of different levels, their combined effect should be considered, rather than the individual effect of each.

• The Fletcher–Munson curves at Wikipedia

Answer 2

The answer to this is really not known. The field of audiology now talks about "hidden hearing loss". This is hearing loss than does not show up in clinical tests. Kujawa and Liberman (2009) found in animal models that sound exposure that has only a temporary affect on the ability of the animal to detect quick sounds, can do permanent damage.

Le Prell et al. looked at this in humans. These are difficult studies to do since you do not want to harm otherwise healthy research subjects. She had subjects listen to music at 94, 99, and 101 dB A for 4 hours. For the 94 dB A group, there was no statistically reliable effects on hearing 15 minutes after stopping the music (ask quick as they could measure anything). For 101 dB A, the effect lasted over a day, but less than a week. It is thought that the 101-dB A 4-hr exposure is safe, but know one really knows yet. Further, the effect of repeated exposures (either before or after recovery) is not known.

What is known is that there is no way to reverse hearing loss. There is no pill you can take. While hearing aids do restore some level of hearing, you should take care of your ears.

Answer 3

Simple answer is, standard says safe exposure of lodness of 85dBSPL is 8 hours. Now the question is how will you measure how loud is safe. While listening with earphone, ask someone to speak to you. If you can't hear them, turn volume down until you can hear them and that's your safety zone. Enjoy your music.