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Potential hearing loss from non occupational noise exposure in headphones and hearphones Raffaele Mariconte1, Diego Annesi2 1
2
INAIL Settore Ricerca, Certificazione e Verifica DIPIA, 00184 Roma, Email:
[email protected] INAIL Settore Ricerca, Certificazione e Verifica DIL, 00040 Monte Porzio Catone, Email:
[email protected] transistorized stereo record player with the KLH Model 11,
Introduction Italian Law T. U. 81/08 obliges the noise exposure assessment about entertainment, music and call centers environments applying specific standards (art. 198). Often, in those sectors we have occupational noise exposure in headphones and headset. Recently, have been published guidelines for music industry and recreational activities with technical report UNI/TR 11450, which provide all technical indications for measurement and assessment of occupational noise exposure including workers using headset. Listening music in headphones and hearphones with portable devices is a widespread phenomenon, born with the advent of the “Walkman” and increased exponentially with the spread of digital devices. That practice concerns mostly teenagers, which are a pre-employment category and which usual listen high volume music. Today’s MP3 players, for example, permit users to listen crystal-clear tunes at high volume for hours on end, through a marked improvement on the days of the “Walkman”. Young people could risk their hearing listening music from personal players for several hours at high volume. For these cases it is difficult to set limitations, if not in regulations for player’s sound power, so it is important training and information about the risks. This work aims to give an overview about the problem and proposes methods for risk prevention through information campaigns.
Figure 1: Technological and commercial evolution timeline of portable music players after Edison’s phonograph
Portable music players: from the origin to state of art and the near future
provided of amplifier and two speakers which all folded neatly into a “suitcase” for easy transportation.
Portable music players system development (figure 1) has always been closely linked to the development of technology (electronic and digital) and music medium (vinyl, tape, CD, MP3).
Philips and Norleco develops in the 1965 the first portable cassette recorders; between the early 1970’s and the late 1990’s, the cassette was one of the most common formats for pre-recorded music.
In the 1877 the phonograph was invented by Thomas Edison; it was the first device to be able to reproduce the recorded sound.
In the 1975, Astraltune launches the world first portable stereophonic tape deck, but the first big revolution happens in 1979 when Sony, the king of miniaturization, released the first truly self-contained portable music system, the TPS-L2 “Walkman” cassette player. The Walkman’s real innovation was its size, measuring only slightly larger than a cassette tape itself. Featuring a pair of portable, lightweight headphones and operating on batteries, it ushered in a new era of portability. The Walkman was the first of a long line of mobile devices to attract criticism (the “walkman effect”) for isolating its users, promoting narcissism, detachment, and rude behavior, while at the same time preventing
In USA in the 1920, the Portaphone permits of music being heard anywhere. In the 1954, I.D.E.A. released the very first portable transistor radio. The Regency TR-1 radio measured 3″x5″x1.25″ and featured an analog AM tuner, played through a low-fidelity monophonic speaker. In the 1962, Henry Kloss developed the very first portable
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AIA-DAGA 2013 Merano interactions that are the basis for traditional place-based communities. In addition, it was the begin of potential hearing loss for large listening music in headphones.
“Soundcloud”, “Grooveshark”, “Mixcloud” etc., today we have available an endless database of music files. It is probable that we are at the beginning of the third big revolution in portable music players.
In the 1982, the first CD for commercial use was produced by Philips and in the 1984 Sony updates its popular Walkman introducing their D-50 portable CD player, the first ever portable digital music player. Just slightly larger than a CD case, the player offered all of the great audio quality that digital recordings had to offer. In the 80’s the “boombox”, a device capable of receiving radio stations and playing recorded music (usually cassettes or CDs) with two or more loudspeakers, quickly became associated with urban society, particularly African American and Hispanic youth. The wide use of boomboxes in urban communities led to being coined the nickname “ghetto blaster”. Soon cities began banning boomboxes from public places and they became less and less acceptable on city streets.
Figure 2: Percentage of each portable audio device sold in 2004-2007 [4]
The magneto-optical disc-based data storage device “MiniDisc” was released by Sony in the 1992; soon Sony updated this new technology in Walkman series. MiniDiscs were very popular in Japan but made a limited impact elsewhere, so that soon it became obsolete.
Several types of headphones/earphones may be used with portable devices and with other fixed equipment (e.g. CD or DVD players, home theater, personal computers etc.). From the first truly successful set (developed by Nathaniel Baldwin, who made them by hand in his kitchen and sold them to the United States Navy in the 1910), that created in the years a strong economic and social impact (a new listening device that allowed you to listen to anything without bothering the people around you), technology has highly evolved until today (figure 3).
In the 1991, the German company Fraunhofer-Gesellshaft creates a new format of compressed digital audio with the ostensible same audio quality of uncompressed digital formats. In the 1993, the MPEG project is officially accepted as a national standard and in the 1995 became an international standard, and the name “MP3” is coined. With the large diffusion of lossy audio format, the second big revolution happens (figure 2). A Korean company called SaeHan Information Systems, creates the very first solid state commercial portable music player in the summer of 1998: the “MPMan”. It was featured a 32 MB of RAM (expandable to 64 MB) and held about 8 average length tracks (around 32 minutes of music). The original iPod, released in 2001 combined a 5GB hard drive with a rechargeable battery pack and a paradigm breaking user interface. Marketed by Steve Jobs as “1000 songs in your pocket,” the iPod didn’t necessarily do that much differently under the hood from other MP3 players, but it had a sleek design, a unique and simple navigational system, and the Apple brand name to back it all up. In 2003, Apple released iTunes and opened their iTunes store, which made it easy to purchase legal music downloads for just 99 cents a track. With their one-two punch of form and function, Apple continues to dominates the portable music player market today. Over the years Apple has continued to release a plethora of new iPod models (3rd Generation, Mini, 4th Generation, Shuffle, Video, Nano, Touch). In the October 2011, Apple reported that total number of iPods sold worldwide was 300 million.
Figure 3: Technological and commercial evolution timeline of headphones
With innovations like touch-screens, high definition video playback, wireless streaming, low cost solid state memory, the advent of iPhone and other mobile devices (smartphones, iPad and other tablet) and mostly the spread of broadband internet access and cloud services such as “Spotify”,
Nowadays, headphones can be divided into the following categories:
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circumaural: have circular or ellipsoid earpads and are designed to attenuate any intrusive external noise; supra aural: have pads that press against the ears, generally tends to be smaller and lighter than circumaural, resulting in less attenuation of outside noise. Both circumaural and supra-aural headphones can be further differentiated by the type of earcups: open-back: have the back of the earcups open. This leaks more sound out of the headphone and also lets more ambient sounds into the headphone, but gives a more natural or speaker-like sound; closed-back: have the back of the earcups closed. They block the ambient noise, but have a smaller speaker-like sound. The earphones can be classified into the following types: earbuds: very small headphones that are fitted directly in the outer ear, facing but not inserted in the ear canal; in-ear: small and without headband, are inserted in the ear canal itself. For the purposes of this article, will be considered the types which correspond to those of most commercial diffusion with portable devices: supra aural, isolator (in-ear) and earbuds.
for the majority of users. However, approximately 5% - 10% of the listeners are at high risk due to the levels patterns and duration of their listening preferences.
Acoustic Level and potential risk from noise exposure
Laws and recommendation on noise exposure
Several studies have been performed until today to evaluate the sound levels produced by different types of portable music players or the noise exposure of users, but almost always with different methodologies and results difficult to compare.
The risk of hearing damage depends on sound level and on exposure time. As a result, listening to loud sounds over many hours per day entails a similar risk as listening to an even louder sound for a shorter period per day. For longterm exposure of workers, time periods of 8 hours per day or weekly sound exposure (8 hours per day for 5 days per week), are typically considered in order to set protections standards.
Output level of music 110
Output Level [dBA]
100
Supra Aural
90
Isolator
80
Earbud
70 60 50 40 30
0
10
20
30
40
50
60
70
80
90
100
Percentage of volume control
Figure 4: Free-field equivalent output level for all genres of music as a function of volume control settings and tree type of headphones [7]
The best estimate suggests that this maybe between 2.5 and 10 million people in EU. Those are the individuals listening to music over 1 hour a day at high volume control setting. It is estimated, also, that the numbers of young people with social noise exposure had tripled (to around 19%) since the early 1980s, whilst occupational noise had decreased.
Some recent studies [1], [2], [7] are based on the MP3 devices. In particular, the study [7] was taken as reference for the subsequent considerations. The purposes of study were to investigate the relationship between volume control settings and output levels of MP3 devices to examine how adolescents’ listening behaviour changes as a function of background noise and noise isolation, to investigate the relationship between self-reported listening levels and laboratory-measured listening levels and to evaluate the validity of the Listening Habits Questionnaire as a research tool for evaluating how attitudes and beliefs relate to MP3 devices use behaviour.
New stringent action levels were introduced in the EU with the Directive 2003/10/EC [5]; it recommends three protection levels at the workplace depending on equivalent noise level for an 8-hour working day: 80 dBA: employers shall make hearing protectors and below this limit, the risk to hearing is assumed to be negligible; 85 dBA: protection of workers is mandatory; 87 dBA: the maximum exposure limit value. NIOSH (National Institute for Occupational Safety and Health) recommends an exposure limit of 85 dBA for 8 hours per day (REL, Recommented Exposure Limit), and uses a 3 dB time intensity tradeoff: for every 3 dB increase in noise level, the allowable exposure time is reduced by half and vice versa [6]. With an exposure of 85 dBA, statistically, there is the 8% of excess risk (the percentage of people in a noise-exposed population who develop a material hearing impairment over a 40-year working lifetime). With exposures respectively of 80 and 90 dBA, statistically, there is the 1% and 25% of excess risk.
By the study, were extrapolated the values of free-field equivalent output level for several genres of music as a function of volume control settings for three type of headphones (figure 4). The study also shows that these devices permit to listen music at high volume for hours on end, therefore the teenagers who use them for several hours a day at high volume, could risk their hearing. These values formed the basis for estimating the daily noise exposure according to two methodologies related and developing the safe maximum listening time per day. According to SCENIHR report [4], the levels in portable music players produce minimal risk of hearing impairment
To develop the safe maximum listening time per day charts, have been used the following formulas of the above criteria:
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NIOSH : T
480 2 LREL 3
1999/5/EC and LV Directives 2006/95/EC that make reference to European Harmonised Standard EN 60065: 2002 “Audio, video and similar electronic apparatus - Safety requirements”. This standard provides the technical detail to ensure the safety of users of personal music players with headphones or earphones. It requires compliance with maximum pressure level and maximum voltage outputs measured following the methods described in standards EN 50332 (shall not deliver more than 100 dB maximum SPL that corresponds with a long time average of 90 dB L Aeq and a maximum output Voltage of 150 mV for the players). None of the standards currently require any specific labelling in respect of noise emissions. In 2005, the French authorities updated a national Order of 1998 aimed at preventing users of personal audio equipment and mobile telephones from suffering long term hearing impairment. It requires information and/or labelling for the end user and the respect of EN 50332.
[min.] (1)
Where: T is duration in min.; L is exposure level in dBA; REL is Recommented Exposure Limit, equal to 85 dBA (80 dBA is a safest treshold); 3 is exchange rate. LEX , 8 h L 10
[min.] (2) 2003/10/EC : Te T0 10 Formula (2) is obtained by inverting the formula(3) T LEX ,8h L 10 log e T0
[dBA] (3)
Where: Te is duration in min.; T0 is 480 min equal to 8 h.; L is exposure level in dBA; LEX,8h is Daily Noise Exposure. It is observed that the two different formulas used lead to similar results. The following charts show some calculation results for different threshold levels.
Conclusions As seen, it is evident that listening music in headphones and hearphones may cause noise exposures comparable or even superior to professional exposure in the workplace, with the difference that, at the time, there are no regulations aimed at preventing the risk. For this reason, it is important to educate teenagers, highlighting the risks of improper use.
Maximum listening time per day [LEX,8h 85] Percentage of volume 10 20 30 40 50 60 70 80 90 100
Isolator
Earbud
No Limit
No Limit
6 h 21 min 1 h 36 min 24 min 6 min
11 h 18 min 2 h 50 min 43 min 11 min
Supra Aural
No Limit
For example, a general rules of thumb are listening volume at maximum ¾ for 1 hour per day, set the volume in non noisy environment and take periodic breaks of 15-20 minutes when listening to loud music to allow ears to recover.
8h 2h 30 min
Table 1: Maximum listening time per day as a function of volume control settings and tree type of headphones according to 2003/10/EC (LEX,8h 85)
References [1] E. Keith, S. Michaud, V. Chiu: Evaluating the maximum playback sound levels from portable digital audio players. J. Acoust. Soc. Am. 123 6, June 2008, (4227–4237)
Maximum listening time per day [REL 85] Percentage of volume 10 20 30 40 50 60 70 80 90 100
Isolator
Earbud
No Limit
No Limit
6 h 21 min 1 h 35 min 24 min 6 min
11 h 19 min 2 h 50 min 42 min 11 min
Supra Aural
[2] A. Farina: A study of hearing damage caused by personal MP3 players. 123rd AES Convention, 2007 October 5–8
No Limit
[3] M. Bull: Sounding Out the City: Personal Stereos and the Management of Everyday Life.
8h 2h 30 min
[4] SCENIHR: Potential health risks of exposure to noise from personal music players and mobile phones including a music playing function Preliminary report.
Table 2: Maximum listening time per day as a function of volume control settings and tree type of headphones according to NIOSH (REL 85) Maximum listening time per day [LEX,8h 80] Percentage of volume 10 20 30 40 50 60 70 80 90 100
Isolator
Earbud
No Limit
No Limit
8h 2h 30 min 8 min 2 min
14 h 14 min 3 h 34 min 54 min 14 min 3 min
[5] Directive 2003/10/EC of the European Parliament and of the Council of 6 February 2003 on the minimum health and safety requirements regarding the exposure of workers to the risks arising from physical agents (noise).
Supra Aural
No Limit
[6] Criteria for a recommended standard Occupational Noise Exposure. DHHS (NIOSH) Publication Number 98-126
10 h 4 min 2 h 32 min 38 min 10 min
[7] Cory D.F. Portnuff, Brian J. Fligor, Kathryn H. Arehart: Teenage Use of Portable Listening Devices: A Hazard to Hearing? Journal of the American Academy of Audiology/Volume 22, Number 10, 2011, (663–677)
Table 3: Maximum listening time per day as a function of volume control settings and tree type of headphones according to 2003/10/EC (LEX,8h 80)
The main European regulatory framework governing the safety of this equipment are the R&TTE Directive 8
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