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The SCENIHR opinion states:
3.7.PMP usage in the population
In the last decade PMPs have become used by an increasing portion of the population. The maximal levels of noise produced by the new generation devices are very high and obviously cause an increased risk of hearing impairment. The factors involved in the potential risk of hearing loss are noise intensity and duration of exposure at a particular level. Listening environment, type of headphones / earphones as well as type of music may play additional roles. This chapter describes the habits of listening to music through PMPs on a regular basis by teenagers, as well as the availability of PMPs. The data provided in this chapter are crucial for a risk assessment.
3.7.1. Listening levels
Several studies are accessible in the literature assessing PMP in terms of maximum sound pressure level measured in dB SPL or dB(A). Already Katz et al. in 1982 warned that stereo earphones could deliver acoustic levels up to 120 dB(A) (Katz et al. 1982). Later in 1985 Lee et al. measured portable headphone cassette radios peak outputs of 90 to 104 dB (Lee et al. 1985).
Rice et al. examined over 60 users of personal cassette players (PCP). They were asked to set the volume control of a PCP to the level at which they would normally listen to different types of music. The ranges of measured sound pressure levels were between 60 and 108 dB(A). Mean free-field equivalent continuous A-weighted sound pressure level (unobstructed field LAeq) was close to 85 dB LAeq, 25% of the sample experienced levels of at least 90 dB (A), and 5% had levels above 100 dB(A) (Rice et al. 1987a).
In the study by Wong et al. the equivalent measured music noise levels were of 56 to 116 dB(A) among 394 PMP users (Wong et al. 1990).
In the study by Turunen-Rise et al. published 16 years ago, A-weighted maximum and equivalent sound pressure levels (SPLs) were measured on KEMAR (Knowles Electronics Manikin for Acoustic Research) system on five different PCPs while playing selected types of music and using different gain (volume) settings. The types of music included pop music, classical music and light classical music. The transformed A-weighted field equivalent SPLs were on average from 75 to 85 dB(A) only (Turunen-Rise 1991).
In the study by Ising et al. sound levels of music played from mini-cassette players via headphones were measured in a nonrepresentative group of 681 pupils whose ages were between 10 to 19 years. They set music levels measure as free field corrected short time Lequ, between 60 dB(A) and 110 dB(A) (Ising et al. 1994).
In a study of social noise in a population sample of representative 18-25 year olds in the UK Smith et al showed that the level of preferred listening on PMP was 74 dB(A) which was 72.6% in the low noise category and 80.3% in those with significant social noise exposure. In the tail of distribution it was found that 6.9% adjusted to levels in excess of 90 dB(A). If adjusting for enjoyment then the average level of adjustment in a quiet room was 85 dB(A) with a mean of 92 dB(A) in those who had significant social noise exposure (Smith et al. 2000).
The availability of portable high-performance digital players, with an increased dynamic range, has facilitated the listening to music at high levels due to reduced distortion at these levels. Some measurements point to the fact that very high acoustic levels could be reached (125-127 dB(A)) with a Lequ, 1h of 110 dB(A) (Loth et al. 1992). The study by Fligor and Cox published in 2004 indicated that for several different styles of headphones/CD players, free-field equivalent sound pressure levels measured at maximum volume control setting ranged from 91 dB(A) to 121 dB(A). Output levels varied across manufacturers and style of headphone, although generally the smaller the headphone, the higher the sound level for a given volume control setting. Specifically, in one manufacturer, insert earphones increased output level by 7-9 dB, relative to the output from stock headphones included in the purchase of the CD player (Fligor and Cox, 2004).
Based on measured sound pressure levels across systems and the noise dose model recommended by National Institute for Occupational Safety and Health for protecting the occupational worker, a maximum permissible noise dose would typically be reached within 1 hr of listening with the volume control set to 70% of maximum gain using supra-aural headphones. Using headphones that resulted in boosting the output level (e.g., insert earphones used in this study) would significantly decrease the maximum safe volume control setting; this effect was unpredictable from one manufacturer to another. According to Fligor and Cox (2004), in the interest to protect the hearing of the majority of consumers, reasonable guidelines would include a recommendation to limit headphone use to 1 hr or less per day if using supra-aural style headphones at a gain control setting of 60% of maximum.
3.7.2. Listening habits
This chapter addresses the habits of music listening regarding the average sound pressure level of music and time spent on listening to music through PMPs in an everyday life. In some of these investigations, individuals were either queried about subjective level to which they set their volume and time spent on listening to music through PMP (how loud/how long) or asked to set the level of an equivalent device in the laboratory setting. In some other studies these measurements were performed in real world situations, which is a more preferable approach rather than extrapolating the data from laboratory studies. Several studies are accessible in the literature assessing PMP sounds in terms of equivalent sound pressure levels and permissible dose of noise. These studies used various study designs and methods of measuring maximum output levels of headphones (artificial ear vs KEMAR system). Because there is no standard for recreational noise, all of them referred equivalent sound pressure levels from music players to the occupational noise standards (ISO 1999:1990 standard).
In the study by Catalano and Levin (1985) 154 public college students in New York City were studied via a self-administered questionnaire regarding the volume setting used and weekly exposure in hours to these units. The values were referred to the “A” weighted scale for permissible noise dose according to OSHA criteria (OSHA publication no.29 CFR 1910). Of all students who used such radios 31.4% (41.2% males vs 29.2% females) equalled or exceeded the maximum allowable dose, with the predominance of males. The mean weekly exposure time of females was 8 hours (+/- 10 hours/week) while of men it was almost 14 hours (+/- 10 hours/week). Of the total “at risk” group 50% exceeded the risk criteria by more than 100%. The authors concluded that portable radios with headphones may be capable of causing permanent hearing loss in a large proportion of radio users (Catalano and Levin 1985).
Rice et al. by referring the levels of sound to the listening times, 5% of the sample were listening in a manner causing that habitual use would constitute a damage risk to hearing. The authors conclude that there could be some damage to hearing from PCP devices if habitually used over long period time (Rice et al. 1987a, 1987b). The shortcoming of this study is that the authors used the admissible daily level of noise of 90 dB LAeq recommended in 80s, while currently it is 80 dB LAeq. Re-evaluating the data it would increase the population at risk to over 10%.
In another early study Wong et al. 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 (Wong et al. 1990).
In the study by Ising et al. nearly 50% of the total group listened to music less than one hour per day, and only less than 10% listened for four or more hours (Ising et al. 1994). Estimating the expected hearing loss (HL) based on ISO 1999 standards, about 10% of the total group were predicted to have a HL more than 10 dB at 4 kHz after 5 years of using personal music devices (Ising et al. 1994). The music habits were evaluated in 569 pre-teens and teenagers by the same group of authors (Ising et al. 1995). They concluded that taking into account only portable music players, one can expect that even after 5 years of music approximately 5% of the total group would have a hearing loss of 20 dB. Based on their assumptions, the authors suggest that decreasing output level of PMP devices to 90 dB(A) would minimise the risk of hearing loss (Ising et al. 1995). In a study by Job et al (2000) it is reported that 39% of young subjects from 18 to 24 years old went to discos more than twice a month and 17% listened to their personal stereos (cassette players, CD) more than one hour a day.
A recent report by Bohlin and Erlandsson (2007) examined risk behaviour and loud music exposure in young 310 adolescents aged 15-20 years. They observed that although women judged risk situations as generally more dangerous than men but they nevertheless behave in the same way. Adolescents reporting tinnitus judged loud music as more risky than those with no symptoms and they did not listen to loud music as with those with occasional tinnitus. They suggest that hearing protection should acknowledge and make use of theories on risk behaviour especially due to the existence of a relationship between adolescents’ risk taking in noisy environments and other types of risk taking.
3.7.3. Listening environments
Rice et al. examined over 60 users of personal cassette players (PCP). They were listening to various music and speech against quiet and noisy backgrounds, in the field and laboratory conditions. There was no significant difference between listening levels for the different pieces of music, but there was a significant increase in the mean listening level from 80.7 dB to 85.1 dB (approximately by 4 dB) in the presence of background noise (Rice et al. 1987a).
Skrainar et al. 1987 found that users of PMP in occupational noise set levels of 70 to 98 dB(A) with an average of about 87 dB(A) which did not significantly add risk (Skrainar et al. 1987).
In the study by Williams (2005) measurement was made in a sample of 55 individuals who were using a PCP as part of their daily activity, when commuting to work, in what could be considered noisy backgrounds (the worst-case conditions). The average, A-weighted, eight hour equivalent continuous sound exposure level from PMP in the worst case condition was determined to be 79.8 dB (80.6 dB in males and 75.3 dB in females) (Williams, 2005). These sound exposures do not indicate a significant increase in the risk of potential sound injury from PMP alone for the majority of the user population. However, there is a subpopulation of individuals who set the volume control of PMPs very high and/or listen to music through PMPs for long hours a day. In the cited study of Williams (Williams 2005), 25% of individuals exceeded the limit 85 dB(A) of noise exposure, while as much as 40% exceeded the level of 80 dB(A).
Recently published study by Hodgetts et al. (2007) indicated that preferred listening levels were higher with earbud earphones than with over the ear headphones but in a group of 38 users in quiet or noisy environments levels settings ranged from 70 to 90 dB(A) only (Hodgetts et al. 2007).
Source & ©:
SCENIHR,
The SCENIHR opinion states:
3.7.4.Market trends and availability of portable audio equipment
The market surveillance information was obtained for this report from GfK (www.gfk.com/
) by MRC Hearing and Communication Group on 14th March 2008. The data comprised all the Domain Product Groups relating to audited unit sales for portable audio equipment for the countries Germany, UK, France, Italy, Spain, Netherlands, Belgium, Austria, Switzerland and Sweden. The coverage period was for 2004-2007 except for CD players which had data from 2001-2007. The overall coverage of sales channels was highest in the UK, but very similar market trends were observed for Europe. The market coverage for UK for MP3 players averaged at 91%, with an average of 80% overall the selected European countries (which total estimated population of 357,239,716 in 2007 or about 71% of EU population). In order to extend these data to the EU countries as a whole two methods were used. The simple method was to multiply the data up on population basis pro rata. In addition to that the data were weighted according to internet access penetration in EU countries (http://epp.eurostat.ec.europa.eu/
, data accessed on April 28 2008). These weighted data could then be used as a broad range with the multiplied up pro rata data to give a position for Europe. Figure 3 shows estimated units sales in EU of all portable audio devices and MP3 devices as a function of estimate procedure over the period 2004–2007. The estimates have been weighted by each country’s take up of the internet or on a pro rata population basis. In addition there has either been allowance for the audited data coverage or not (on an annual basis where available, otherwise on an average basis for that medium).
This figure shows that for all portable audio devices the unit sales were in the range 184‑246 million units, while for MP3 devices the units sales were estimated as about 124 million but could be as large as 165 million. This equates at the top end to units sales equivalent to 1:2 of the population. So, it is assumed that some people buy more than one device in that time period.
The overall number of audio devices sold in the ten countries and in the EU as a whole is shown in Fig 4. This shows the overall increase in sales in 2005 that has been maintained in the following two years, with more than 50 million devices being sold per year by 2007. Figure 5 shows that the PMP player sales were responsible for that increase. The percentage of MP3 players sold as proportion of all portable audio devices has increased dramatically from over 20% to over 80% in the last three years (from 2004 to 2007), and in 2007 it consisted of over 30 million unit sales in ten European countries* (vs of 10 million for CD players at its peak in 2004) (fig.5).
The sales data, not adjusted for coverage, for MP3 players and for all audio devices are shown in Figure 6. These data show the large increase in unit sales for the MP3 players over the 4 year period from audited figures and from those estimated for the EU countries.
Figure 7 shows the proportion of portable audio devices sold in 2004-2007, which indicates that about 67% of all portable audio devices sold were MP3 players, with 17% being CD players.
Figure 8 shows the percentage of each portable audio device category sold in 2007 and the estimated numbers sold in that year. It shows that the percentage of MP3 players was about 83% in 2007 compared to 67% over the four year time period. Clearly this proportion of MP3 players will increase over time.
In addition to the data on portable audio the increasing importance of the use of mobile telephone equipment, with high quality audio facilities (very similar if not the same as MP3 players) was examined. These data are very sensitive to market variations and there are no data in terms of the exact availability and use of the mobile phones (Gartner Inc.).
The data suggest that in Q4 of 2007 there were 55 million mobile phone handsets sold in ‘Western Europe’, which on a pro rata basis (about 28% units sales in 2006 and 2007 worldwide) gives a 2007 sales of 192 million. This is equivalent to about 161 million in EU countries. It is estimated that presently about 10-20% of these phones may have smart features such as MP3 players. This will increase rapidly so that up to 75% of all phones sold by 2011 may have features similar to the MP3 players available now on the market. So in rough terms an estimate might currently be that 16 to 32 million devices (and hence probably close to that in terms of people) have access to these sorts of emerging “hi technology” features. Data are not very precise at present and it is not clear at all whether people who have access to these features actually use them.
Although the data for the portable audio market are accessible, there are no demographics easily available on these sales, nor any information on how many devices an individual may buy over a given time period, how long they last before being discarded and how long and in what situations they are used. Thus, it is hard to estimate the proportion of the population that has access to portable audio or to MP3 players, and how many use them on daily basis. However, it may be estimated in a rather conservative way that in EU a number of daily users of devices like personal music players and mobile phones with this function could be very high and in the range of 50 - ‑100 million.
3.7.5. Conclusions
The levels of exposure to sounds from PMP range widely from 80 dB(A) to 115 dB(A) among PMP users, while mean weekly exposure time ranges from below 1 to 14 hours, and is typically longer for men than for women. The type of music and environment may influence exposure levels.
There is a literature evidence that, the average, A-weighted, eight hour equivalent sound exposures levels from PMPs range between 75 to 85 dB(A). Assuming that music as a cause of noise-induced hearing loss could be compared with industrial noise, such exposures produce minimal risk of hearing impairment for the majority of PMP users. However, a small proportion of users are at a higher risk due to the levels patterns and duration of their listening preferences. Considering the daily (or weekly) time spent on listening to music through personal music players and the typical volume control settings, approximately 5% to 10% of the young listeners are at high risk of developing permanent hearing loss after 5 or more years of exposure.
The increase in unit sales of portable audio devices mainly MP3 has been phenomenal in EU over the last four years. Estimated units sales could be in the range 184‑246 million for all portable audio devices and in the range 124‑165 million for the MP3. The increase overall in sales was noted in 2005 and has been maintained in the following years with more than 50 million devices being sold per year by 2007.
The yearly sales of mobile phones reach a similar number of units. However, at present the availability of the MP3 functionality is not widespread in these handsets (e.g. may be ten percent). Its use is even more unknown. So, at present the major risks to hearing, if use is inappropriate is through portable audio devices, and particularly through the very large numbers of people using MP3 players.
* Austria, Belgium, Germany, UK, France, Italy, Spain, Netherlands, Sweden and Switzerland (see Figure 5)]
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SCENIHR,
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