Music to your ears: is it a good thing?

Music is a wonderful thing. It lifts the spirit, transports us to other worlds and helps us express emotions for which we have no words. Many quotes supporting the role that music plays in our lives have entered every-day English use: ‘If music be the food of love, play on’ (1). When Shakespeare wrote those lines, you had to travel on foot, horseback or carriage to hear a band or orchestra or see a play. Now however, music is as close as your computer, MP3 player or telephone. In Shakespeare's time, music made you laugh, cry, dance or sing; it did not make you go deaf. Music today also makes you laugh, cry, dance or sing; but now, if you listen long and loud enough, you eventually won't be able to hear it.

A recent article in Nature Neuroscience discussed data suggesting that portable music players may damage hearing, but that the true probability of MP3 players causing permanent hearing loss remains unclear (2). Decades ago, investigators found that the human ear, when exposed to loud sounds long enough, will permanently lose some hearing. The outer hair cells in the cochlea, when exposed to loud noise, initially experience transient damage that causes a temporary threshold shift in the hearing; if the person is exposed long enough, the damage becomes permanent. Standard pure tone audiometric tests do not capture these early changes, so by the time you can ‘see’ the hearing loss in the audiogram permanent damage has been done. Governmental agencies, including The Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH) have long-established guideline for occupational and industrial noise exposure, and requires that the individual workers exposed to sound levels greater than 85 dB wear ear protection. These guidelines are based on a calculation of noise ‘dose’, using formulae that include total time of exposure at a specific noise level. These guidelines show how, above 85 dB, the potential for permanent hearing loss increases rapidly with seemingly modest increases in decibel level (Table 1). As decibels are measured on a logarithmic scale, this is not surprising, and the chart shows that for every 3-dB increase in sound pressure, the amount of allowable exposure time is cut in half (3).

Technology has made music, news, videos and other media instantly available. Personal cassette players (PCPs) were introduced in the 1970s, CD players in the 1980s and MP3 players in the late 1990s. Apple Corporation (Cupertino, CA, USA) has sold over 110 000 million of their MP3 player, the iPod^®, since they were introduced in October 2001. MP3 players are often listened to for several hours at a time, due to long battery life and huge storage capacity, making changing tapes or CDs (and therefore turning them off) unnecessary. People listen to MP3 players in the gym, on the subway, on airplanes and in many other noisy situations. This causes the user to turn the MP3 player up even louder to overcome background noise. Although MP3 players are most popular with teens and young adults, because of their light weight and great versatility in storing all kinds of music and other media, however, they are becoming more popular with younger children and adults of all ages as well. Hearing loss due to noise exposure is therefore no longer limited to construction workers, hunters and rock musicians; now anyone can get it.

The potential dangers to hearing secondary to portable music players have been well appreciated since the 1980s. A study published in 1987 asked 500 school children in Turin, Italy, to complete a questionnaire about their listening to their PCPs (how many hours per week, the type of music they listened to, and where they used the device). The average age of the listeners was 15.7 years, 5% listened more than 19 h per week and 5% were exposed daily to sound levels greater than 90 dB. However, using a formula that calculated that 1.3% of individuals exposed to 90dB over a period of 10 years would develop permanent hearing loss, they estimated that only 1/1500 would develop permanent hearing loss; given these very conservative assumptions, this may represent an underestimation of the actual risk. None the less, the authors were concerned that 5% of the population was exposed daily to sound levels of greater than 90 dB, well above the current hearing damage-risk guidelines (4).

An additional risk was identified in a report published in 1996. The authors assessed people using PCPs in different background noise situations. They found that the average PCP was set to exceed 85 dB when the background noise exceeded 72 dB, translating to a mean 0.5 dB increase in listening level for each decibel rise in the level of background noise (5). As the average background noise level of an occupied cafeteria is 85 dB and the interior of a moving car 40–80 dB (depending on road surface, etc), it is easy to see why people might turn up their music players.

A 2004 report found that the output levels of common earphones, including insert, supra-aural, vertical and circumaural varied across type and manufacturer, but generally the sound pressure level in decibels was highest for the smallest earphones, and that insert earphones increased the output level 7–9 dB. In a few CD player-headphone combinations, output exceeded 130 dB. Currently, all common MP3 players can produce sound pressure levels of more than 100 dB using the earbuds supplied with the players. A recent 2007 article recommends that the people using a standard personal music player and headphone combination should limit their listening to no more than 60% volume for 60 min (or less) for a CD player and no more than 90 min (or less) at 80% volume for a MP3 player during any 24 h period. Additional recommendations are to use sound-isolating earphones in the presence of significant background noise (and if difficulty hearing your background noise does not pose a safety issue). The use of these earphones has been shown to provide as much as 25 dB of sound isolation, and therefore most people keep the volume down (6,7).

In summary, although the exact epidemiological risk of hearing loss secondary to the use of personal music players is unclear, it is very real. However, personal noise exposure cannot be regulated like industrial noise exposure. Paediatricians need to be aware that their patients are at prominently increased risk of hearing loss and that asking about use of MP3 players might begin a dialog that could prevent hearing loss.

Parents should be aware of the risk for themselves and their children, and be good role models by practicing ear protection in noisy situations (e.g. lawn mowing). If they are not vigilant, they will have to face the music in terms of their hearing.