Editor’s note: Content for this article was adapted from Fink D., Mayes J. Unsafe at any sound: Hearing loss and tinnitus in personal audio system users. Proc. Mtgs. Acoust. 43, 004003 (2021); https://doi.org/10.1121/2.0001452, with the permission of the Acoustical Society of America. All references for statements made are contained in the original article from which this manuscript is adapted.
In 1965, pioneering consumer activist Ralph Nader published “Unsafe at Any Speed: The Designed-In Dangers of the American Automobile,” 1 informing the public that automobiles were inherently unsafe to drive because of their design. Similarly, personal audio systems (PAS), also called personal music players or personal listening devices, are inherently unsafe to use because of their design, delivering high-intensity sound directly to the ears with users almost always listening at sound output levels high enough to overcome ambient noise. PAS include audio content source devices such as MP3 players or smartphones used with transducers such as earbuds or headphones. Like automobiles, risk of use can’t be eliminated completely, but PAS can be made safer to use.
Although older PAS users are not immune to auditory damage, here we focus on younger users. PAS use causes noise-induced hearing loss (NIHL) and tinnitus, with the World Health Organization estimating that 1.1 billion young people aged 12-35 are at risk of hearing loss from PAS use and recreational noise exposure. 2 Early onset hearing loss has lifelong negative consequences, affecting interpersonal relationships, self-esteem and mental health, cognitive health, educational achievement, and future employment success.
NOISE AND AUDITORY RISK
The dangers of occupational noise exposure for hearing have been known for centuries, but the fact that nonoccupational noise exposure also caused hearing loss wasn’t recognized until recently. 3 Noise risk is highest for cumulative episodes of unsafe sound exposure over a person’s lifetime, even when interspersed with periods of quiet. 4 Hearing loss risk estimates are based on occupational noise-exposed unprotected adults aged 18-65. To our knowledge, there are no similar studies of noise exposure and hearing loss in children or teenagers, but the developing auditory system is likely more susceptible to noise damage. 5
Due to research ethics against noise/damaging studies in human subjects and inconsistent definitions and methodologies in available PAS user data, noise risk relationships are unclear for tinnitus, hyperacusis, and hidden hearing loss (HHL). These impairments typically develop earlier than NIHL. HHL includes auditory disorders not detected at standard audiometric frequencies, such as speech-in-noise performance deficits, impaired cochlear function on otoacoustic emissions testing, and extended high frequency (EHF) hearing loss. 6
The LEQ or equivalent continuous average sound pressure level (SPL) is considered the best metric for average noise measurements. The evidence-based, nonoccupational noise exposure to prevent NIHL, for the median of the adult population, is only 70 A-weighted decibels (dBA) daily average based on a 24-h time period (LEQ24h). 7,8 A-weighting adjusts decibel measurements to approximate the human auditory response to sound, although C-weighting may better measure music’s low frequency bass sound energy. Safe sound exposures to prevent tinnitus and HHL must be ≦70 dBA, given their association with NIHL. Occupational noise exposure limits should never be applied to the public since they are not protective enough for cumulative lifetime exposures, particularly for high-risk or noise-sensitive populations such as children. 9
PAS SOUND OUTPUT
PAS volume settings of 50%-60% correspond to approximately 70 dBA to 80 dBA mean SPL, 2,10 but exposure during use is highly variable since different PAS produce different sound outputs at the same volume control settings. 11 For example, at 80% volume, SPL ranges from 76 dBA to 94 dBA LEQ depending on the device and earbud or headphone combination. PAS produce up to 126 dB SPL maximum sound output. 4
Personal listening volume setting is related to individual preferences, music frequency characteristics, and improving the signal-to-noise ratio (e.g., overcoming ambient noise while taking public transit). People using stock earbuds often listen at higher sound levels in noisy environments than people using headphones, deeper fitting earbuds, or transducers with noise reduction or isolation technology. 12 PAS headphones with an 85 dB volume limit are available, often falsely advertised as safe for children’s hearing.
PAS USER AUDITORY IMPAIRMENTS
As detailed in our recent paper, 13 PAS use is ubiquitous in younger people worldwide, with some users listening as much as 12 hours a day and others listening even in their sleep. Many listen at high to maximum sound levels. Average noise exposures during PAS use in different listening situations are shown in Table 1.
PAS use begins as young as age 3. 14 A study of >10,000 Canadians found prevalence of PAS use was >29% at age 6, 59% at age 9, 80% at age 12, and 85-95% from ages 12-19. 15 Almost all studies show that PAS users have higher prevalence of auditory disorders than nonusers, with auditory damage found in children as young as age 9-11. 16 Sensorineural auditory impairments in PAS users include impaired pitch discrimination, tinnitus, HHL, and high-frequency hearing loss characteristic of harmful noise exposure.
The prevalence of hearing loss and tinnitus in PAS users increases over time. Fewer than five years of PAS exposure is associated with HHL indicators (e.g., impaired otoacoustic emissions and EHF hearing loss); >5 years’ exposure is associated with NIHL, with PAS users at about four times higher risk of NIHL than non-users. 17 Systematic reviews have identified the greatest auditory risk for PAS use >1 hour daily >50% volume for at least one year. The WHO reported that nearly half of young people aged 12-35 listen at >50% volume levels. 2 In the United States, the average user listens 4.5 hours daily. Auditory risk is highest in young PAS users who typically listen the most regularly, for longer time periods, at high volume.
Tinnitus is a characteristic symptom of auditory damage. Tinnitus incidence of about 28% in PAS users is significantly higher than about 8% in nonusers. 4 Temporary tinnitus was found in 74.9% and permanent tinnitus in 18.3% of almost 4,000 high school juniors with loud music exposure, including PAS. 18 In 18- to 35-year-olds using PAS at high volume, approximately 75% reported tinnitus, 40% reported worsening hearing problems over time, and 20% reported frequent difficulty understanding conversations in various social situations including family dinners. 12
PAS MANUFACTURER STANDARDS
Noise-induced auditory impairments in PAS users might be reduced by harmonized global manufacturer sound limit standards, but these are unlikely to be mandated. The WHO and International Telecommunication Union recommended sound allowances of 40 hours weekly exposure at 80 dBA for adults and 75 dBA for sensitive users such as children. 19 To prevent NIHL from recreational sound, Neitzel and Fligor recommended daily exposure limits of 70 dBA LEQ24h for sensitive populations such as children and 75 dBA LEQ24h for adults. 20 We think lower daily limits are safer—65 dBA LEQ24h for sensitive PAS users, i.e., children, and 70 dBA LEQ24h for adult users. Unfortunately, that may not be high enough to overcome ambient noise in many everyday listening environments. Even the lower recommended sound exposures may not be safe enough to protect auditory health fully from permanent noise damage. Looking for a safe PAS may be like looking for a safe cigarette—one won’t find one—but lower sound outputs are definitely safer than higher ones.
UNSAFE AT ANY SOUND?
Are current PAS unsafe at any sound, with billions of PAS users worldwide at risk of auditory damage, just as pre-Nader era automobiles were unsafe at any speed? Unfortunately, the answer appears to be “yes.”
Without engineered PAS sound output limits, safer listening approaches include restricting PAS use in childhood, using well-fitting transducers with noise-canceling or limiting features, and listening at the lowest comfortable volume setting below 50%. If possible under device controls, users should set audio output as low as possible and activate parental controls to lock that output level. If the PAS has noise-monitoring features that give unsafe listening alerts, users should keep their volume low enough not to trigger warnings.
These approaches are unlikely to protect the public because they rely on user motivation instead of mandatory PAS sound output limits. Public education campaigns may convince parents to protect young children’s hearing, but programs aimed at convincing PAS users to reduce listening volumes have been largely unsuccessful. Despite programs such as Make Listening Safe and Dangerous Decibels, studies continue to show increasing prevalence of auditory symptoms in PAS users over time.
Effective noise control measures to protect PAS user auditory health should include mandatory engineered PAS sound output limits, unified volume step output increases, default startup at lower rather than higher sound exposures, and warnings when sound exposure exceeds non-occupational daily 24-h limits. Warning labels stating, “THIS DEVICE MAY CAUSE HEARING LOSS,” like the warning labels on cigarette packs, may alert users or their parents to the inherent dangers.
With PAS use, society has the largest unprotected noise-exposed population since before occupational noise exposure standards were introduced in the 1970s. While PAS users might think they can set PAS listening volumes to avoid auditory injury, high sound output designed into PAS makes personal listening inherently unsafe. American automobile manufacturers resisted prioritizing safety in vehicle design until Congress passed the National Traffic and Motor Vehicle Safety Act in 1966, increasing government regulatory oversight over the auto industry. Similarly, progress in preventing noise-induced auditory impairments is unlikely without federal legislation. Without regulated PAS sound limits, preventable tinnitus, HHL, and NIHL will continue to increase in children, teenagers, and young adults.
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2. World Health Organization. 2021 World report on hearing Geneva WHO Licence: CC BY-NC-SA 3.0 IGO. https://www.who.int/publications/i/item/world-report-on-hearing
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14. Canadian Health Measures Survey (2012-2013). Hearing loss of Canadians, 2012 and 2013. https://www150.statcan.gc.ca/n1/pub/82-625-x/2015001/article/14156-eng.htm
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