9. How can listening to music harm hearing?
- 9.1 Is hearing loss increasing among young people?
- 9.2 Can using personal music players raise the hearing threshold?
- 9.3 Is tinnitus more frequent among users of personal music players?
- 9.4 How can attending concerts and night clubs affect hearing?
The SCENIHR opinion states:
3.8. Effects of sound from PMP on hearing
Noise pollution remains the most frequent environmental hazard accounting for hearing loss. Over the last years an increasing exposure to noise has been noted outside workplace, during recreational/leisure activities. The latter affects not only adults, but also children and adolescents (Plontke et al. 2004). Personal music players were widely introduced to the market in 1980s first as cassette players, and in 1990s as CD players. In the 21st Century, MP3 and currently i-Pods have become very popular. Most PMP users are teenagers and children. Although the equivalent levels of exposure to noise from using these devices on regular basis seem to be substantially lower than e.g. from discos or rock concerts (Serra et al. 2005) they continue to be a concern in the mainstream media. The question is whether or not loud sounds from personal music players including mobile phones with a music playing function could raise a potential risk to hearing loss? This chapter describes the changes in prevalence of hearing loss in young people that could be attributed to increasing environmental noise exposures, as well as the influence of listening to the music through PMPs on hearing threshold shift, either temporary or permanent.
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9.1 Is hearing loss increasing among young people?
The SCENIHR opinion states:
3.8.1.Changes in prevalence of hearing loss in young people
Majority of epidemiological studies on the hearing, including very recent ones, failed to prove an increased prevalence of hearing impairment in teenagers and young adults over the last decades (Strauss et al. 1977, Carter et al. 1982, Persson et al. 1993, Axelsson et al. 1994, Augustsson and Engstrand 2006, Rabinowitz et al. 2006) or did not find a correlation between leisure time activities and hearing impairment (Axelsson et al. 1981, Axelsson 1994, Mostafapour et al. 1998, Tambs et al. 2003). It has been shown that from 5% to almost 20% of young individuals have audiometric “notches” at 4-6 kHz consistent with noise exposure, but this rate has remained constant over the last 20 years (Wong et al. 1990, Meyer-Bisch 1996, Niskar et al. 2001, Axelsson et al. 1981, Axelsson et al. 1994, Peng et al. 2007, Rabinowitz et al. 2006). These studies were performed in German, Australian, Swedish and American populations where the PMP were very common.
Three cohort studies reported increasing prevalence of hearing loss in young individuals over the last 30 years, i.e. during the period when PMP have been extensively used since the 1980s. Montgomery and Fujikawa reported in 1992 that over a decade second graders with hearing loss has increased by 2.8 times, and eighth graders had an increase of 4 times (Montgomery and Fujikawa, 1992). Danish children starting school in 1977, 1987 and 1997 were evaluated for hearing ability by a review of 1,605 school health records (Gissel et al. 2002). Higher prevalence of impaired hearing ability in children who started school in 1987 and 1997 compared to those who started school in 1977 was found; in addition at the end of school year group 1977 hearing had become as poor as that of year group 1987. Reduced hearing was typically at high frequencies, indicating to noise-induced hearing impairment (Gissel et al. 2002).
Boys and girls (aged 14–17 years) were examined during a four-year period. Audiological, psychosocial, and sound measurements were performed yearly to determine the hearing threshold level (HTL) of participants in the 250–16.000 Hz range, their participation in recreational activities, and the sound levels at discos and through personal music player use. A tendency of the mean HTL to increase in both genders during the study was observed, especially at 14.000 Hz and 16.000 Hz. Boys had a higher mean HTL than girls. The participation in musical activities increased yearly, `attendance at discos' being the favourite musical activity for both groups. In general, boys were more exposed to high sound levels than girls. In this 4-year longitudinal study it was concluded that the exposure to high sound levels during leisure activities (but not necessarily from PMP) could be a cause of permanent hearing damage among young people with “tender ears” (Biassoni et al. 2005).
Although epidemiological literature data does not support the view that there is wide-spread hearing loss caused by exposure to amplified music in young people under the age of 21 years, some authors stress that if the recreational pattern remains the same, there could be some risk of noise-induced hearing loss by the age of mid-twenties (Carter et al. 1982). Slight alterations of hearing function have been detected as possible early signs of ear impairment before deficits were detected with classical audiometry by frequency selectivity and high definition audiometry (West and Evans 1990, Meyer-Bisch 1996), otoacoustic emissions (LePage and Murray 1998) and very high frequency audiometry (Peng et al. 2007). However no follow-up data is available for these studies.
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9.2 Can using personal music players raise the hearing threshold?
The SCENIHR opinion states:
3.8.2.Hearing threshold shift
In the population with increased risk of hearing impairment from personal music players either temporary hearing threshold shift (TTS) or permanent hearing threshold shift (PTS) may develop. TTS may result from short (few hours) exposures at the levels near the maximum output of the music device. PTS may result from repeated exposures (over years) to moderate sound levels exceeding allowable dose of noise.
126.96.36.199. Temporary threshold shift (TTS)
Only few studies have been published on temporary hearing threshold shift due to music sounds from personal music players. They were mainly laboratory investigations on the healthy volunteers overexposed to sounds.
In a pilot study by Lee et al. 16 volunteers listened to headphone sets for 3 hours at their usual maximum level. Six of them showed TTS of 10 dB at one or more audiometric frequencies, and one volunteer showed a TTS of approximately 30 dB at 4 kHz. These shifts returned to normal within 24 hours in all individuals. The average post-test music sound level ranged from 94 to 104 dB SPL (Lee et al. 1985).
In the study by Turunen-Rise et al. the TTS was measured in 6 volunteers with normal hearing (3 males and 3 females aged 23-40 years). They were exposed for 1h to pop music (that generated the highest noise level among all types of music tested) at the gain setting of 8 on the scale. Corresponding field levels of music sound ranged from 85 to 95 dB(A). A small notch at 4 kHz (2-3 dB on average, no more than 15 dB) was observed after exposure to pop music with moderate use of percussion instruments, while significantly more TTS was observed with the pop music extensively using percussion instruments. The highest exposures produced greatest TTS. Hearing impairment recovered completely within 20-40 min. for the majority of subjects (Turunen-Rise et al. 1991).
In the study by Loth et al (1992), 12 volunteers listened to two recordings (classical music and hard rock) at an acoustic level complying with safety regulation. TTS at 4 and 6 kHz were measures just after exposure and it was, on the average 5 dB. No difference between frequencies and type of music was found.
188.8.131.52. Permanent threshold shift (PTS)
Permanent threshold shift that could be related to music players was investigated by several authors in the field studies designs. Both, positive and negative findings were published.
The first study evaluating the potentially harmful effects of amplified music on young people’s hearing was published in early 80’s of 20th Century, and failed to prove hearing impairment (Carter et al. 1982).
In their study Wong et al. (1990) assessed the prevalence of use of personal cassette players among youths in a residential community in Hong Kong. They interviewed 487 individuals aged 15-24 years, with 394 (81%) reported using PCP regularly (i.e. for 3 days or more in a week for at least 6 months). The mean duration of PCP use was 2.8 years, and the mean listening time was 4.5 hours per week. Among the 78 PCP users and 25 non-users examined with pure-tone audiometry, no significant difference in the mean hearing threshold was observed for the frequencies tested (250-8000 Hz). However in the studied group, only four subjects were habitually exposed to sound levels higher than 85 dB(A). One was exposed to 116 dB(A) and was found to have a 4000 Hz dip on his audiogram. The authors conclude that despite the high prevalence of PCP use, most youths used their PCP at relatively safe sound levels with low risk of hearing loss (Wong et al. 1990).
Similar results were obtained by Kawada et al in 1990 and West et al. (1990). In the first study no significant differences between mean hearing acuity between PMP users and non-users were found in 155 medical students aged between 22-29 years. However, the mean hearing acuity at 4 kHz showed a tendency of being lower in users than non-users, and higher percent of individuals with hearing impairment was found in the user group as compared to the control. The authors suggest that 10% of the young generation is at risk for permanent hearing loss from use of portable music players (Kawada et al. 1990). In the second paper, sixty subjects in the 15-23 age range were examined. While the most exposed groups did not show significantly greater averaged thresholds, there was a significantly increased prevalence of notches in the 3.5-6 kHz audiograms of the older age group (West, 1990).
The concern about safety of PMPs arose after publication of the study by Meyer-Bisch (1996). The investigation involved young people 14-18 years who were just discovering music played loudly. Three subgroups were defined for users of personal cassette players: occasional, 2-7 h/week and >7 h/week. High definition audiometry (449 frequencies over the spectrum from 125 to 16000 Hz) was applied and early warning indicator (EWI) was calculated from the arithmetic average of the thresholds at 3, 4 and 6 kHz. The groups were matched according to disco attendance, PCP use and concert attendance. PCP users were defined as those who never or only occasionally go to rock/variety concerts or discotheques, but who use a PCP for at least 2 h/week. In total 249 individuals from 14-30 years of age (mean 17.7) were assessed including 54 individuals (21.7%) with the use of a PMPs for at least 8 h/week (majority of them were 15-16 years old subgroup). A statistically significant increase of average hearing thresholds was found in people using PMPs > 7 h/week (54 subjects) as compared to those using PCP 2-7 h/week (195 subjects) and as compared to their matched control. The differences were significant at the range of frequencies from 2 to 12 kHz. From the same study of Meyer-Bisch, it could be concluded that only the individuals with high rate of using PMPs (more than 7h/week) develop significant permanent threshold shift. On the other hand, subjective auditory suffering signs (tinnitus, hearing fatigue) were found to be three times more frequent in the PMPs listeners group than in PMPs non-users, suggesting that may be pure-tone audiometry is not the most sensitive method of discovering subclinical or early damage to the cochlea.
More sensitive approach to detect subtle changes in hearing due to exposure to noise is to assess otoacoustic emissions (OAEs). OAEs are thought to be affected early, before clinical signs appear (LePage and Murray 1998, Mansfield et al. 1999, Rosanowski 2006, Shupak et al. 2007), and are simpler to record, thus offering a possible monitoring and educational tool.
In 1998 LePage and Murray applied transient-evoked otoacoustic emission (TEOAE) to assess the effects of personal stereo systems on hearing. Usable records were obtained from 1724 people (1066 males and 658 females) aged between 10 and 59. The level of TEOAE was significantly lower in PMPs users than non-users, although only small proportion (39 people) of PMPs users admitted any hearing problems. For the teenage range (10-19 years) there was no significant difference between non-users, those who used PMPs below 1 hour per week and those who wear PMPs from 1 hour to 6 hours a week. However, for the group of people aged 20-29 and more both users groups was significantly different from non-users group. The authors conclude that the decline in otoacoustic emission strength forewarns premature hearing loss in PMPs. They also suggest that hearing impairment from PMPs music occurs only in the late-teenage and early-adult period (LePage and Murray, 1998). While interpreting the data of LePage and Murray, one should conclude that preclinical phase of hearing loss and relatively short length of time of exposure prior to hearing evaluation (early teen-age) are probably two factors justifying why some previous studies failed to observe any effect of music on hearing.
The other methods of early detection of NIHL applied to occupational noise-exposed population include extended high frequency audiometry and Bekesy audiometry. The studies that used these tools in PMP users were positive. Dieroff et al (Dieroff et al. 1991, Peng et al. 2007) examined 181 persons aged between 16 and 18. The group of individuals using PMP often revealed a significant change in hearing threshold at the audiometric frequencies above 8 kHz; it was also true for the disco attending population. Early elevation in thresholds was also better detected by high resolution Bekesy tracking than by conventional fixed-frequency audiometry in the group of sixty subjects in the 15-23 age range examined by West et al. (West et al. 1990).
More recently published studies are again equivocal. In a prospective auditory testing of fifty college volunteers with retrospective history of exposure to recreational noise, no difference in pure-tone threshold, speech reception threshold or speech discrimination was found among subjects when segregated by noise exposure (Mostafapour et al. 1998). No significant effects of frequent use of personal music players or regular attendance at disco and rock concerts was also demonstrated in the Norway survey of 51,975 adult participants performed in 1995-1997 (Tambs et al. 2003). Similar results were obtained in a subcohort of 358 young (18 year old) adults with a history of otitis media; use of PMPs had no effect on hearing (de Beer et al. 2003). On the other hand, based on audiometric testing of 120 personal music players users and 30 normal-hearing young adults it was revealed that hearing thresholds in the 3 to 8 kHz frequency range were significantly poorer in the group using PMPs (Peng et al. 2007). Also, in some of the PMPs users, the hearing thresholds were worse with high-frequency audiometry even if their hearing thresholds in conventional frequency audiometry were normal (Peng et al. 2007).
3.8.3. Speech comprehension impairment
In the only study on fifty college volunteers with retrospective history of exposure to recreational noise, no differences in speech reception threshold and speech discrimination was found among individuals when segregated by noise exposure (Mostafapour et al. 1998).
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9.3 Is tinnitus more frequent among users of personal music players?
The SCENIHR opinion states:
There are numerous reports of high levels of music-induced tinnitus in young people (Holgers et al. 2005, Chung et al. 2005, Axelsson et al. 2000, Davis et al. 1998, Widén and Erlandsson 2004, Rosanowski 2006). However, only three studies compared the rate of subjective complaints of hearing problems and tinnitus in PMPs users. Two studies were positive showing that these signs were more frequent in walkman users (Becher 1996, Meyer-Bisch 1996). In the study by Meyer-Bisch auditory suffering (AS) was assessed using two subjective parameters – presence of tinnitus (even temporary) and/or hearing fatigue. Auditory suffering was two times significantly more frequent in PCP users (2–7 h/week) than in matched control group. Such difference was not confirmed in those using PCP > 7 h/week, although in PCP group twice as many individuals had some complaints relative to the control group (Meyer-Bisch 1996). In the more recent investigation no correlation between the exposure to PMP and self-reported hearing loss and/or incidence of tinnitus was found (Williams 2005).
9.4 How can attending concerts and night clubs affect hearing?
The SCENIHR opinion states:
3.8.5.Risk associated with pop concerts and discotheques
The data from these studies are presented here since the acoustic levels of exposure are quite similar to those that could be achieved with PMP. However, the sounds being delivered in free field are subject to many more fluctuations as exact position of the ears from the sound sources changes whereas for PMPs no such fluctuations of position from sound sources occur.
In 1977 and 1978 Axelsson and Lindgren published a review of previous studies (5 reports from 1967 to 1974) which indicated that on a total of 160 pop musicians examined only 5 were found to have a hearing loss. They also reported their own observations on 83 pop musicians exposed on average for about 9 years 18 hours a week to levels of up to 115 dB(A); small hearing losses were observed in 13-30% of the subjects depending on the definition of hearing loss; the authors concluded that the risk of NIHL was very small. These authors also indicated that after two hours of pop music pop musicians exhibited TTS for levels starting at 98 dB(A) whereas normal listeners started to have TTS for a level of 92 dB(A), this difference seeming only partly explainable by the original slight elevation of hearing of pop musicians (Axelsson and Lindgren 1978b). Irion (1981) described one case of acute bilateral hearing loss while attending a pop concert followed by almost complete recovery within a few days, this exceptional vulnerability was attributed to genetic predisposition.
Two epidemiologic surveys were reported by Babisch and Ising (1989), one on 204 the other on 3133 young people, showed that those with some hearing loss indicated on average more time spent in discotheques. Such a relation was later confirmed by Dieroff et al. in 1991, within a group of 181 persons (Dieroff et al. 1991). Those who went more than three times a month to discos showed on average a slightly greater loss at very high frequencies. In 1992 Drake-Lee measured TTS in a group of four pop musicians after a concert in which levels could be up to 135 dB(A), with less TTS for those who wore ear defenders. In 1996 Liebel et al. observed TTS of up to 10 dB on average after 2 hours of attendance to a discotheque for two hours at an average level of 105 dB(A). Meyer-Bisch (1996) states that although 211 discotheques patrons did not show audiometric damage, people having gone to rock concerts at least twice a month exhibited some hearing losses. Metternich and Brusis (1999) examined 24 patients consulting after musical acoustic trauma, in two thirds of the patients the hearing loss occurred after a one-time exposure to a pop concert, in the other third the loss occurred after repeated attendances to discotheques or parties, five patients reported tinnitus. In a study on 46 employees in discotheques with at least 89 dB(A) average acoustic level, Lee (1999) observed a higher prevalence of hearing loss and tinnitus as compared to a control group. Sadhra et al. (2002) report on 14 students working in entertainment venues exposed to more than 90 dB(A) and up to peak levels of 124 dB(A), small but significant TTS was observed. In a study by Bray et al. (2004) on 23 dance music disk jockeys three exhibited dip losses of NIHL type in their audiogram and sixteen reported TTS and tinnitus after job sessions. Among eighty-eight young adults with normal hearing and no tinnitus Rosanowski et al. (2006) indicated about 20% reporting tinnitus after visiting a disco and about 50% reporting a transient hearing loss. Schmuziger et al. (2006) examined 42 non professional pop/rock musicians exposed for at least five years and compared with a control group of 20 non exposed matched subjects, on average a small but significant hearing loss was found in pop/rock musicians, eleven of the musicians were hypersensitive to loud sounds and seven reported tinnitus. Stormer and Stenklev (2007) reviewed seven publications on pop musicians emphasising prevalence of permanent hearing loss, tinnitus hyperacusis and increased resistance to loud music. Finally Schmuziger et al. (2007) indicate in 16 non professional rock/pop musicians a TTS after rehearsal of 90 minutes at a mean acoustic level of 103 dB(A), the TTS affected usual audiometric frequencies while surprisingly very high frequencies were not affected.
Meecham and Hume (2001) questioned 545 students attending night clubs and showed a significant association between attendance at night clubs and duration of post-exposure tinnitus. Non-attendees were significantly less likely to get spontaneous tinnitus.
Overall the data concerning NIHL, associated with pop concerts and discotheques, presents some analogies with those presented above for PMPs. The range of acoustic levels of exposure is can go higher, however the duration and number of times of exposures is smaller. Short term studies clearly demonstrate reversible hearing losses after exposures. The studies started about 30 years ago so that rather long-term data are now available and there is no clear evidence that prevalence of NIHL linked to pop concerts has increased significantly over the last 30 years.
3.8.6. Risk associated with classical orchestral music
In classical orchestras sound levels are on average considerably less than in pop concerts but in some music pieces may also be quite high for long durations and thus musicians appear to be also at some risk of NIHL. A few studies only have dealt with assessment of this risk. Westmore and Everdsen (1981) found slight hearing losses of the notched NIHL type in about a third of 68 musicians, acoustic recordings during rehearsals revealed levels in excess of 90 dB(A) in only 4 hours out of a total of 14 hours. Johnson et al. (1986) tested 60 orchestral musicians in comparison with matched non musicians and they found no difference in hearing sensitivity even at very high frequencies. In contrast Ostri et al. (1989) tested 95 orchestral musicians and found hearing losses in 58% of them in the form of a NIHL type notched audiogram. McBride et al. (1992) did not find clear evidence for NIHL in 36 musicians. Assessment of hearing in 62 choir singers indicated some hearing losses mostly at low frequencies in contrast with the usual pattern of NIHL. From audiometric testing of 140 classical orchestral musicians Kahari et al. (2001) did not find clear evidence for NIHL related hearing losses. Laitinen et al. (2003) measured sound levels for a variety of instrument players and playing conditions, during performances individual exposure levels could be 95 dB(A) while at rehearsals levels could be 100 dB(A).
These studies indicate that for classical musicians involved in classical music acoustic levels of exposure exceed occasionally risk thresholds, but there is no undisputable evidence for an associated NIHL.
It seems that the majority of young users of personal listening devices are at low risk for a substantial NIHL.
The risk of permanent sensorineural hearing loss arises from repeated, regular daily exposures to high sound levels.
Excessive acute exposures to PMPs music at maximal or near maximal output volume can produce reversible hearing impairment (temporary threshold shift) up to 30 dB at 4 kHz in some individuals after short time (one or more hours) of exposure. However, the risk of hearing loss and tinnitus is much smaller compared to pop concerts and discotheques music exposures.
There are major discrepancies between the results of the studies on permanent NIHL in PMP users. They could arise from different study designs and methodology. Most of these studies showed none or only small permanent effect of using PMP on hearing in the majority of users, if short term consequences were assessed with audiometric hearing threshold. A lack of long-term studies and with using more sensitive hearing outcomes, like for example otoacoustic emissions makes it difficult to conclude whether the exposure to PMP music in teenage may influences hearing in older age.
Overall the data concerning NIHL, associated with pop concerts and discotheques, presents some analogies with those presented above for PMPs. The range of acoustic levels of exposure can go higher, however the duration and number of times of exposures is smaller. Short term studies clearly demonstrate reversible hearing losses after exposures.
Studies for classical musicians indicate that their level of exposure occasionally exceed risk threshold, but there is no undisputable evidence for an associated NIHL.
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