2013 Vol.8 No.1

NOISE INDUCED HEARING LOSS IN CHINA: A POTENTIALLY COSTLY PUB-LIC HEALTH LSSUE

Shi Yongbing , William Hal Martin

AbstractHearing loss and tinnitus are among the most common consequences of long term noise exposure and re-

main an under-addressed heath issue in most developing nations including China. The rapid industrializa-tion and life style changes in China increase the concern over noise exposure and noise induced hearing loss(NIHL). Research on NIHL in China is limited. The current paper reviews studies published in English andChinese language literatures regarding noise exposure and NIHL in China. Their implication on the Chi-nese population is discussed. The possible utility of a research model such as the Dangerous Decibels® as ameans to increase understanding of the scope of NIHL among the Chinese population, to educate the gener-al public in China (especially the young) about NIHL and its prevention, and to study effects of languageand cultural factors on international information dissemination and behavioral interventions is proposed.

Key words: noise, noise-induced hearing loss, China

Introduction

Noise hazard can cause many health problems. Hear-ing loss and tinnitus are among the most common conse-quences of long term noise exposure. Other health is-sues such as anxiety and hypertension have also been re-ported to be related to noise exposure. While noise haz-ard has been extensively studied in industrialized coun-tries, it remains an under-addressed heath issue in mostdeveloping nations including China. China is the largestdeveloping country in the world. As it is rapidly industri-alized in the past few decades, occupational noise expo-sure and noise exposure in daily life among its popula-tion are on the rise and there is an increasing concernover the potential health consequences of such expo-sures. In recent studies, in addition to other environmen-tal factors such as lack of relaxation and physical exer-cise, frequent extra work shifts and air pollution, noisepollution is ranked number four to contribute to asub-healthy status in the Chinese population[1]. Noise ex-posure has also been shown to be a significant determi-nant of hypertension prevalence in China, trailing only

family history and salt use[2].China is going through probably the fastest change in

its recent history, with rapid growth in economy and dra-matic alterations in ordinary people’s life styles. Suchchanges have significantly changed individual Chinese’sexposure to noise levels on a daily basis among manyother changes, involving his/her working environment,transportation and leisure time activities. Tens of mil-lions of immigrant workers in Chinese cities are mostlyinvolved in labor-intense trades including constructionand manufacturing, often subjecting themselves to noiselevels higher than typical office environment. As mil-lions of Chinese now commute to work and movearound in motor vehicles instead of bicycles, streets inmost Chinese cities and towns are getting increasinglynoisy. Entertainment activities among young Chineseare drastically different than former generations and of-ten involve loud sound exposures, including music, sportevents, computer games and other loud hobbies. The in-creased noise exposure levels of the Chinese populationinevitably raise the questions on its impact on hearingand hearing disorders in China.

Affiliation:Oregon Hearing Research Center NRC043181 SW Sam Jackson Park Road, Portland, OR 97239,USA

Corresponding authors:SHI Yong-bin，Email：shib@ohsu.edu

JOURNAL OF

OTOLOGY

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Hearing loss in China

Systematic study data on the prevalence of hearingloss in China are scarce. For the purpose of this review,some non-peer reviewed online data are quoted in con-junction with those from peer-reviewed academic jour-nals.

Hearing-related disabilities have been reported to beamong the most common disabilities in China, affecting16.8% of the population[3]. A recent survey in the south-west province of Sichuan that involved 126,876 random-ly selected individuals suggested an overall hearing lossprevalence of 3.28%, with 73% of the cases being senso-rineural[4]. In the same province, the rate of profounddeafness had been reported to be at 0.186%, with 35.6% ofthese cases being attributed to environmental factors[5].Among senior Chinese populations, prevalence of hear-ing impairment appears to be higher. In a study conduct-ed at the beginning of the 21st century in Suzhou, amid-size city in southeastern China, prevalence of hear-ing loss was reported to be at 66.5% among urban se-niors and 50.5% among their rural counterparts. Whilethe rate of disease-related hearing impairment was simi-lar in the two groups, the rates of presbycusis andnoise-induced hearing loss (NIHL) were significantly dif-ferent: 55.8% versus 43.4% and 6.5% versus 0.8% re-spectively, with the rate in the urban group being higherthan that in the rural group[6].

Little data are available concerning hearing disordersin young Chinese. About 0.3% of newborns in Chinaare reported to have hearing disorders[7, 8]. A Sino-Japa-nese group studied hearing impairment among schoolage (7-17 years) children in a rural area in a northernChinese province (Shandong) in 1996. Of the 282 chil-dren studied, 56 (20% ) were found to have abnormalhearing and more than half of the hearing loss ears eitherdemonstrated a 4000 Hz notch or were dominated byhigh frequency loss. The prevalence of hearing loss inthis group of Chinese children is significantly higherthan young Japanese or even the normal data of youngpeople in the same province in 1987[9].

NIHL in China

Data regarding epidemiology of NIHL in China arevery limited. A thorough literature search of English lan-guage biomedical databases yielded only 9 published pa-pers regarding NIHL among the Chinese population inpeer reviewed journals. More epidemiological studiesare published in the Chinese language literature and thevast majority of these works are concerned with occupa-tional NIHL in China.

The past three decades have witnessed rapid industrial-ization in China. Small scale factories and enterprises

have played a major role in the process since Chinachanged its economic policies that traditionally favoredstate-owned large enterprises. From 1978 to 1991, thenumber of small scale enterprises in China increased11.5 times and the number of employees in such enter-prises increased 2.4 times. Many of such new enterpris-es are privately owned, located in traditionally rural ar-eas and not tightly regulated. Most township enterprisesdo not provide basic occupational health services. Astudy showed that the coverage of five occupationalhealth service activities routinely provided for Chineseworkers was very limited in township enterprises, from1.4 to 36%[10]. The same study showed that 82.69% of ru-ral industrial enterprises had at least one type of occupa-tional hazard in their work environments. Workers en-gaged in at least one type of hazardous working environ-ment accounted for 33.91% of the blue-collar workers.The total detectable rate of the seven types of occupation-al diseases was 4.4% among these workers. In addition,11% had illnesses suspected of being (though not provento be) caused by occupational exposures.

Currently available study data on NIHL in China pub-lished in Chinese language literatures appear to confirmthe impact by noise in the occupational environment.The prevalence rates of noise related deafness among Chi-nese workers from various industries, including manufac-turing, textile, metal works, railroad and packing, rangefrom 12.15 to 49.02% in reported Chinese studies [11-20].The incidence of NIHL increases as the duration of expo-sure increases[11, 16, 19-21]. Prevalence of NIHL as high as80.7% has been reported in railroad workers with a work-ing career longer than 10 years[15].

However, industrial noises are no more the onlysource of noise exposure in modern day China. In thepast 10 years, China has seen the largest scale of roadconstruction and fastest increase in the number of auto-mobiles. Road noise is increasingly a source of noise ex-posure for urban Chinese[22]. A recent study showed thatthe average day-to-night noise level was 79.2 dB (A) inrooms facing main traffic in Beijing, China’s capitalwith fast growth in population and road traffic, danger-ously approaching OSHA safety limit especially giventhat this is a non-stop constant exposure[23]. As economi-cal conditions for the Chinese people improve, increas-ing amount of time is spent on entertainment, especiallyamong young Chinese. Many of these leisure activitiesinvolve exposure to loud sounds, including music andsports events. Some of the Chinese traditional music in-struments are loud and believed to be able to affect hear-ing. In fact, an earlier study suggested that the incidenceof hearing impairment among musicians of Chinese op-era was even higher than among those of popular musicor rock and roll music[24]. Peak sound levels from Chi-

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nese firecrackers have been measured at more than 160dB even at a distance of 2 meters[25]. A recent web-basedsurvey involving residents from the UK, France, Swedenand China showed that 8% of respondents reported hear-ing loss as "a very big problem" on a Likert scale. Mostof these respondents had experienced tinnitus or hearingimpairment attending concerts (61% ) and/or clubs(43% ). Only 14% of respondents had used earplug[26].With improving economic conditions and increasing rec-reational activities for the ordinary Chinese, it can be pre-dicted that average noise exposure levels related to lei-sure time activities in China will continue to increase.

NIHL in Chinese Children

The increase of noise-related hearing impairmentamong young Chinese is probably more alarming, al-though systematic studies in this area are extremely rare.Since noise and NIHL research has traditionally focusedon workers in hazardous environment, little systematicresearch efforts have been directed to studying effects ofnoise exposure on children in China. However, some in-formation seems to indicate increasing hearing problemsamong young Chinese populations. From a report by theTianjin Occupational Disease Prevention Hospital, asmuch as 80% of the young people disqualified for em-ployment were due to hearing problems. They suspectedthat this was related to use of personal listening devicesand frequent visits to loud places such as discos and in-ternet café[27]. A study conducted in Baise City, Guangxi(a southwest province less urbanized than coastal citiesand towns), attests to a similar problem. In this study, 1,156 young people between 13-22 years of age were stud-ied with questionnaires and pure tone audiometry. Theresults showed that 64.2% of the sample listened to theirMP3 players for more than 10 hours/week. Tinnitus and/or hearing impairment following MP3 player listeningwere reported by 12.3% of the subjects, of whom 31.7%showed hearing loss on audiometric tests. The authorsalso concluded that MP3 player use at inappropriate lev-els was likely the cause of their observation[28]. In anoth-er study conducted in Hong Kong that involved 487youths aged 15-24 years, 394 (81% ) reported using thepersonal cassette player on a regular basis, with a meanduration of 2.8 years and a mean time of listening of 4.5hours/week. The mean ear canal sound level was foundto be at 70.4 dB A. In one child, the ear canal sound lev-el was found to reach 116 dB A and he was found tohave a 4000 Hz dip on his audiogram[29].

Little is known about the prevalence and incidence oftinnitus among the Chinese workers and general popula-tion, except for the few reports mentioned above. How-ever, tinnitus is commonly associated with hearing loss

and can be a devastating condition in some cases. Stud-ies in mostly developed countries suggest that preva-lence of tinnitus among the general population is about15% and increasing[30, 31]. It is reasonable to assume simi-lar or worse tinnitus prevalence in China. Tinnitus willlikely become a significant problem for China if hearingloss continues to increase in the country.

The Significance of NIHL in China

The significance of NIHL in China is probably greaterthan in some other countries, considering China’s popu-lation of 1.3 billion and its efforts to develop its econo-my and to improve living conditions for its people. Inaddition to the loss of productivity and life quality to NI-HL, the cost of rehabilitation for hearing-impaired indi-viduals can be un-proportionally heavy for China as alarge developing country. Of major hearing aid brandssold in China, the Oticon hearing aids carry relativelylow prices. Prices of Oticon hearing aids in China rangefrom $240 to $3,400 per piece depending on the model,with a median price at $919[32]. Assuming that 0.186% ofthe 1.3 billion Chinese population have profound hearingloss that require hearing assistance 5, more than $ 4.4 bil-lion will be needed to just fit the 2,418,000 people eachwith two median price Oticon hearing aids. The realcost to help these people is certainly higher since someof these people will not be able to benefit from hearingaids due to the severity of their hearing loss and will like-ly need more costly solutions such as cochlear implants.Albeit China has enjoyed probably the fastest economicgrowth in its history for the past couple of decades, per-sonal wealth in China remains far behind compared tomajor developed countries, mainly due to the size of itspopulation and wealth distribution patterns. The Interna-tional Monetary Fund estimated that China's annual percapita income in 2008 was equivalent to $3,180[33]. Pro-viding appropriate care for increasing numbers of indi-viduals with hearing loss can be a significant drag onChina’s economic development. In addition to financialburdens, the significance of loss of employment and pro-ductivity due to hearing impairment can be tremendousto China as a country that needs to support 20% of theworld’s population, which is also rapidly aging.

What Is Being Done in China for NIHL

While there have been government regulations in Chi-na, they have not always been strictly followed or en-forced. This is especially true in small size privatelyowned enterprises in China, which counted for 60% ofthe Chinese manufacturing industries in 2005[34] and nowemploy a major portion of China’s labor force. To makethe matter worse, little attention has been paid to non-in-

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dustrial noise levels in China’s national standards andrecommendations. Compared to western nations, littleresearch efforts have been made to understand the scopeof NIHL among the Chinese population. This is especial-ly true with non-occupational NIHL. Information onprevalence of NIHL is of great importance as it can pro-vide incentives for relevant legislation and fiscal invest-ment, and guide future research and regulation efforts.

Currently, several legislations governing environmen-tal noise issues, including the Environmental ProtectionLaw of The People’s Republic of China and Environ-mental Noise Pollution Prevention and Control Law, arein place, although enforcement of these laws varies great-ly from region to region. They are better aware of andimplemented in large cities such as Beijing and Shang-hai, and are largely ignored in smaller municipal jurisdic-tions and rural areas. The relatively lack of research andinformation on noise exposure and associated health is-sues have provided little incentive for more effective reg-ulation on the part of the authority, nor does it encouragechanges in practice patterns by business owners or be-havioral changes among the general public. Consideringthe size of the Chinese population and potential cost ofNIHL to the Chinese society, there is a great need for ac-tive research and effective intervention to reduce likelyincreasing impact of NIHL on the Chinese population.

In recent years, there appears an effort in China toraise public awareness of the danger of noise exposure.Whether this is related to increased contact between Chi-na and other developed nations in the world is not clearbut possible. As a result, the third day in March is nowset to be a National Ai Er (Love the Ear) Day in China.The Chinese media usually increase coverage on ear dis-eases, noise exposure and prevention and treatment ofcommon hearing disorders, on this day[35-37]. In recentyears, there has been an increasing concern over hearingproblems and noise exposure levels among the youngpopulation in China[38, 39]. There also seems to be an ef-fort in China to educate the young about noise hazards.

A group of middle school students actually conducteda study on noise levels at a wide range of public loca-tions frequented by the youth. Their data were publishedon the web in 2003, in which they registered a range ofaveraged noise levels from 44.6 dB in a quiet office tosustained 83.1 dB at entertainment places such as gam-ing halls and discos[40]. They concluded that most publicplaces were noisy, including supermarkets (>70 dB) andmarket streets (>82 dB). The report cited crowding andinappropriate use of loud speakers as some of the causesof these high level noises. The group also expressed con-cerns over increasing traffic noises (66-78 dB) and theireffects on commuting school age children and residentialareas neighboring main traffic.

Research That May Help Prevent and De-crease NIHL in China

Despite the above-mentioned efforts, systematic re-search is needed to comprehend the scope of the prob-lem, develop effective intervention instruments, assessimpact of interventions, and monitor trends of NIHL forthe Chinese population. Constant surveillance of noiseexposure and NIHL among the population is needed associal and industrial lives constantly change. In additionto obtaining updated information on the prevalence andincidence of NIHL, it is important to understand factorsthat contribute to NIHL. To achieve this goal, appropri-ate research tools need to be developed and updated toensure acquisition of accurate and relevant information.The tools must also be appropriate to the Chinese lan-guage and culture for them to be effective in the countr

As previous studies have suggested, noise exposure inmodern society is no longer limited to occupational activ-ities. As a result, research on noise exposure and NIHLmust not simply focus on workers in manufacturing en-terprises, but include the general population and their en-vironment. Young people including children of variousages especially need to be studied, as early identificationof problems provides an opportunity for early interven-tion and potentially improved outcomes, and is consis-tent with principles of preventive medicine. Successfulcontrol of noise exposure will be the most cost-effectiveintervention for NIHL. Research of noise exposure inchildren is especially important as they are in a periodcritical for developing long term behavior patterns. Thisis probably the best opportunity to nurture behaviors thatmay lead to lasting voluntary protection against NIHL.As indicated in previous studies, in addition to social anddemographic factors, behavior patterns can also affect anindividual’s attitude to noise exposure[41]. Informationregarding non-occupational noise exposure is especiallyimportant also because such environments are more dy-namic and difficult to regulate than in industrial settings.

How Research Models Such As Danger-ous Decibel® May Be Useful in China

Dangerous Decibel® is a hearing health promotionpartnership initiated by a group of hearing scientists atthe Oregon hearing Research Center (OHRC), which fo-cuses on noise exposure, NIHL and its prevention inschool age children and the general public. It is a jointeffort by the OHRC, the Oregon Health & Science Uni-versity Department of Public Health and Preventive Med-icine, Oregon Museum of Science and Industry, PortlandState University and the University of Northern Colora-do. The project takes a non-traditional approach thatcombines efforts from research institutions, the public ed-

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ucation system and public museums to reach the targetpopulations. Innovative technologies such as videogames and disguised sound level meters are used to en-gage subjects for data acquisition and intervention atpublic locations. Data from over 56,000 individualshave been collected[42]. As part of the project, efficacy ofstructured curricula intervention at schools in reducingrisky behaviors is studied[43]. The project has beenshown to be effective in improving knowledge levels onnoise and NIHL among teenagers[44].

Similar research may also prove to be helpful in Chi-na, although modification and changes are likely neededto make it language- and culture-appropriate. Comparedto traditional approach to noise-related research effortswhich are usually conducted exclusively by either engi-neering personnel or hearing scientists, the DangerousDecibel® model incorporates school system and publiceducation and entertainment facilities. It also allows di-rect intervention among school age children and informa-tion dissemination to the general public in both orga-nized and informal environments. This research modelis not a passive observation of the study subjects, as inmost existing noise-related studies in China, but seeks in-tervention and evaluation of intervention efficacy as anintegrated part of the research efforts. Information fromstudies like Dangerous Decibel® will likely provide newdirections of noise research as well as practical guidancefor NIHL intervention. In addition, the research modelalso serves to study and monitor noise-related issuesamong the population as other traditional noise studiesdo. If successful, a Dangerous Decibel-like project inChina will help increase the information body on preva-lence of NIHL in China and provide an opportunity forearly intervention in NIHL among the world’s largestpopulation. In addition, testing a new research model inthe Chinese language and culture itself is of great signifi-cance. Experience from such endeavor will help pro-mote similar research efforts in other nations. It also pro-vides an opportunity to study impact of language and cul-tural differences on behavioral research. Consideringthe potential society burden of NIHL in China and in-creasing noise hazards around the world, such studiesshould be of high priority and urgency.

References

[1] Xie YM, Liu BY, Piao HY. 2006. [Exploration on the commoncharacters of sub-healthy people based on clinical epidemiology].[Chinese] Zhongguo Zhong Xi Yi Jie He Za Zhi-Chinese Journalof Integrated Traditional & Western Medicine. 26(7):612-6.[2] Zhao Y, Zhang S, Selvin S, Spear RC. 1993. A dose-response re-lationship for occupational noise-induced hypertension. Schriften-reihe des Vereins fur Wasser-, Boden-, und Lufthygiene. 88:189-207.[3]http://www.hb.xinhuanet.com/health/2009-03/04/content_

15853105.htm[4] Liu XZ, Xu LR, Hu Y, Nance WE, Sismanis A, Zhang SL, XuY. 2001. Epidemiological studies on hearing impairment with ref-erence to genetic factors in Sichuan, China. Annals of Otology,Rhinology & Laryngology. 110(4):356-63.[5] Liu X, Xu L, Zhang S, Xu Y. 1993. Prevalence and aetiologyof profound deafness in the general population of Sichuan, China.Journal of Laryngology & Otology. 107(11):990-3.[6] Tang Y, Bu X, Yao Q, Xie Q, Qian M, Hu Y, Yu Y. 2001. [Audi-ological findings of the aging across the urban and rural of Su-zhou]. [Chinese] Lin Chuang Erh Pi Yen Hou Ko Tsa Chih-Jour-nal of Clinical Otorhinolaryngology. 15(7):315-7.[7]http://www.hb.xinhuanet.com/health/2009-03/04/content_15853105.htm[8] http://www.39kf.com/focus/ktpd/2007-03-02-329395.shtml[9] Luo WZ, Miyashita K, Takeda S, Wang YX, Li SC. 1996.Hearing impairment among young Chinese in a rural area. Morio-ka I. Public Health. 110(5):293-7.[10] Zhi S, Sheng W, Levine SP. 2000. National OccupationalHealth Service policies and programs for workers in small-scaleindustries in China. Aihaj. 61(6):842-9.[11] Liu X, Guo Z, He J, Liang Y, Feng J. 2008. [Study on thedose-response relationship for noise-induced hearing loss in work-ers using individual hearing protection]. [Chinese] Zhong Guo ZhiYe Yi Xue-China Occupational Medicine. 35(6):477.[12] Wang J, Gao J, Wang R. 2007. [A survey on career years andoccupational noise-induced hearing loss]. [Chinese] Ting Li Yu Yu-an Yu Ji Bing Za Zhi-Journal of Audiology and Speech Pathology.(15): 458.[13] Chen H, Lin L, Liu L, Liu Q, Lai L. 2006. [A survey onnoise-induced hearing loss]. [Chinese] Xian Dai Yu Fang YiXue-Modern Preventive Medicine. 33(6):948.[14] Xia Y, Wang Q, Li Y, Mu H, Wu X. 2006. [Investigation onnoise induced hearing loss for locomotive drivers in Wulumuqirailway board]. [Chinese] Tie Dao Lao Dong An Quan Wei ShengYu Huan Bao-Railway Labor Safety and Environment Protection.33(6):293.[15] Liu L, Kang W. 2007. [Hearing among locomotive drivers].[Chinese] Lin Chuang Yi Yao Shi Jian-Clinical Medicine Practice.15(10):180.[16] Cai Y, Zhang W, Chen S. 2005. [Study on Noise InducedDeafness in Five Metals Factory]. [Chinese] Hebei Medicine. 11(10):875.[17] Zhong Y, Xie W, Chen P. 2005. [A survey on noise exposurein four industries in Gongguan]. [Chinese] Zhong Guo Zhi Ye YiXue-China Occupational Medicine. 32(6):61.[18] Du W, Zhang R, Hou M. 2005. [An investigation on noisehazards in the the cement enterprises]. [Chinese] Zhi Ye WeiSheng Yu Ying Ji Jiu Yuan-Occupational Health And EmergencyRescue. 23(3):150.[19] Lu J, Shao L, Wang J, Yang Y, Huang Y, Zhu W, Zhao Y.2003. [The dose-response relationship between noise exposureand prevalence of noise-induced hearing loss in man aircraft main-tenance workers]. [Chinese] Zhong Guo Gong Ye Yi Xue ZaZhi-Chinese Journal Of Industrial Medicine. (5):277.[20] Tu B, Gui L. 2000. [Study on Noise Induced Deafness in Lin-en Textile Factory]. [Chinese] Gong Ye Wei Sheng Yu Zhi YeBing-Industrial Health And Occupational Diseases. 26(2):9.[21] Liou SH. 1994. Occupational disease profile in Taiwan, Re-public of China. Industrial Health. 32(3):107-18.

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[22] Ma G, Tian Y, Ju T, Ren Z. 2006.Assessment of traffic noise pol-lution from 1989 to 2003 in Lanzhou City. Environmental Monitor-ing & Assessment. 123(1-3):413-30.[23] Li HJ, Yu WB, Lu JQ, Zeng L, Li N, Zhao YM. 2008, Investiga-tion of road-traffic noise and annoyance in Beijing: a cross-section-al study of 4th Ring Road. Archives of Environmental & Occupa-tional Health. 63(1):27-33.[24] Bu G. 1992. [Prevention of noise induced hearing loss in mu-sicians of Chinese opera]. [Chinese] Chung Hua Erh Pi Yen HouKo Tsa Chih - Chinese Journal of Otorhinolaryngology. 27(2):73-5, 124.[25] Smoorenburg GF. 1993. Risk of noise-induced hearing lossfollowing exposure to Chinese firecrackers. Audiology. 32(6):333-43.[26] Chung JH, Des Roches CM, Meunier J, Eavey RD. 2005.Evaluation of noise-induced hearing loss in young people using aweb-based survey technique. Pediatrics. 115(4):861-7.[27] ebh.ewsos.com/2008/12/3548.html[28] Li J. 2008. [A survey on hearing among the youth in BaiseCity]. [Chinese] You Jiang Min Zu Yi Xue Yuan Xue Bao-Journalof Youjiang Medical College for Nationalities. 30(5):823.[29] Wong TW, Van Hasselt CA, Tang LS, Yiu PC. 1990. The useof personal cassette players among youths and its effects on hear-ing. Public Health. 104(5):327-30.[30] Axelsson A, Ringdahl A. 1989. Tinnitus--a study of its preva-lence and characteristics. Br. J. of Audiol. 23(1), 53-62.[31] Nondahl DM, Cruickshanks KJ, Wiley TL, Klein R, KleinBE, Tweed TS. 2002. Prevalence and 5-year incidence of tinnitus

among older adults: the epidemiology of hearing loss study. Jour-nal of the American Academy of Audiology. 13(6):323-31.[32]http://www.china-hearing.com/new/0_jg_odk.asp[33]http://www.economywatch.com/world_economy/china/in-come.html[34]http://news1.jrj.com.cn/news/2005-12-15/000001385514.html[35]http://www.39kf.com/focus/ktpd/2007-03-02-329395.shtml[36]http://www.hb.xinhuanet.com/health/2009-03/04/content_15853105.htm[37]http://longhoo.net/gb/longhoo/news/nanjing/yiwei /userob-ject1ai934915.html[38]http://epaper.tianjinwe.com/tjrb/tjrb/2007-01/31/content_193825.htm[39]http://www.39kf.com/focus/ktpd/2007-03-02-329395.shtml[40]http://www.pep.com.cn/czdl/xszx/xxyd/xlw/200312/t20031230_72087.htm[41] Yu L, Kang J. 2008. Effects of social, demographical and be-havioral factors on the sound level evaluation in urban open spac-es. Journal of the Acoustical Society of America. 123(2):772-83.[42]http://www.dangerousdecibels.org/resultshearingloss.cfm[43] Folmer RL, Griest SE, Martin WH. 2002. Hearing conserva-tion education programs for children: a review. Journal of SchoolHealth. 72(2):51-7.[44] Griest SE, Folmer RL, Martin WH. 2007. Effectiveness of"Dangerous Decibels," a school-based hearing loss prevention pro-gram. American Journal of Audiology. 16(2):S165-8161

(Received July 25, 2013)

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