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   Abstract
  Introduction
  Methods
  Results
  Discussion
  Conclusion
  Acknowledgments
   References
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ARTICLE  
Year : 2013  |  Volume : 15  |  Issue : 64  |  Page : 199-203
Musicians' ability to judge the risk of acquiring noise induced hearing loss

Department of Clinical Science, Intervention and Technology, Division of Ear, Nose, and Throat Diseases, Unit of Technical and Experimental Audiology, Karolinska Institutet, Stockholm, Sweden

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Date of Web Publication21-May-2013
 
  Abstract 

The objective of this research was to study musicians' abilities to estimate the risk to obtain a hearing loss. Twenty-two professional musicians mainly playing classical music wore dosimeters during 2 working weeks. They also wrote a diary describing all their musical activities and tried to judge the percentage of time that every activity was harmful to their hearing. Half of the musicians seemed to be capable to reasonably judge the harmfulness of the music that they were exposed to. They started to judge the levels to be risky at 80 dB(A) and regarded themselves as sligthly more susceptible to noise induced hearing loss than normal.

Keywords: Judgement, musician, noise induced hearing loss, sound level

How to cite this article:
Hagerman B. Musicians' ability to judge the risk of acquiring noise induced hearing loss. Noise Health 2013;15:199-203

How to cite this URL:
Hagerman B. Musicians' ability to judge the risk of acquiring noise induced hearing loss. Noise Health [serial online] 2013 [cited 2014 Jul 28];15:199-203. Available from: http://www.noiseandhealth.org/text.asp?2013/15/64/199/112376

  Introduction Top


Exposure to excessive loud noise is one of the most common causes of hearing loss and tinnitus. It has been estimated that 16% of late-onset hearing loss in adults worldwide (9% in Western Europe) is due to occupational noise. [1]

Professional musicians are often exposed to sounds, which are loud enough to risk causing a hearing impairment after many years of exposure. In comparison to other professions, they are dependent upon exceptionally good hearing in their work. There are many studies of the sound exposure of professional musicians. Behar et al. [2] reported that 78% of the music teachers were exposed to sound levels exceeding 85 dB(A), when measured with a noise dosimeter between half a day and an entire day. If normalised to a working day of 8 h (L EX,8h ), this level was exceeded for 39% of the teachers. Jansson and Karlsson [3] measured the sound level at various positions within a symphony orchestra. They stated that "the permitted noise dose is reached for 'heavy' music after a working time of 10 h per week in 'exposed' positions, such as in front of the trumpets, and after 25 h in 'normal' positions." Royster et al. [4] found an 8-h daily Leq ranging from 75 to 95 dB(A) with a mean of 85.5 dB(A) for a symphony orchestra. Laitinen et al. [5] performed noise dose measurements on opera musicians and concluded that the sound exposure level exceeded the national action level value of 85 dB(A) for all instrumentalists except for the double bass players. The most exposed were percussionists and flautists with an equivalent sound pressure level of 95 dB(A). However, Lee et al. [6] carried out similar measurements on opera musicians and concluded that the yearly dose was harmless for the whole group. They explain the difference from the results of Laitinen et al. with different exposure times in the two studies, 300 and 800 h per annum, respectively. Kähäri et al. [7] measured sound levels with a noise dosimeter microphone near the ear on four musicians (two playing jazz music, two playing rock music). Equivalent levels between 101 and 115 dB(A) were measured during their performance.

However, we found no studies regarding the ability to subjectively judge the absolute level, in dB(A), of the sound or the harmfulness of the sound. There are a few studies on judged continuous changes of the sound, e.g., Kuwano and Namba, [8] and there are of course also many studies on annoyance of various types of noise. Dittrich and Oberfeld [9] concluded that their listeners were capable of separating annoyance and loudness of the stimuli. It is also well known that the loudness of sound events can be well predicted by the physical properties of the sound events. [10] Since musicians are expected to be especially aware of the various properties of sound, we thought that at least some of them might be able to judge the harmfulness of music sounds.

The present project, all in all, included questionnaires, diaries, and thorough hearing measurements on 121 professional musicians. However, in this first article, we present only results of 22 subjects in a substudy. It contained a comparison of sound expositions during 2 weeks of work, measured by the dosimeter, with the corresponding judgements of the risk of noise induced hearing loss (NIHL).


  Methods Top


Test subjects

The subjects were recruited by advertising and through musicians' personal networks. After the hearing measurements and answering the questionnaires all of them were asked to wear a dosimeter during 2 weeks of work and to fill in a diary during these weeks. Most of them thought that it would be too complicated. However, there were 25 subjects fulfilling this task. Only results from 22 of them, 12 males and 10 females, playing principally "classical" music, are included in this presentation. (The other three played other types of music).

Questionnaire

The questionnaire consisted of 37 questions divided into three main categories, questions about music, e.g., instruments, type of music, hours playing per week, the size of the musician's orchestra or band, questions about their hearing, and questions related to the risk of damage to their hearing. Most of the responses, however, will not be presented in this article, except regarding one question about their expected susceptibility to acquire NIHL: "The risk of acquiring a hearing impairment caused by loud sounds is very variable among individuals. How susceptible do you think that you are regarding hearing impairment due to loud sounds if you compare yourself to other people? Please indicate with a vertical line on the scale below". The scale is shown in [Figure 1]. [11]
Figure 1: The scale used for judging the individual susceptibility of acquiring a hearing loss caused by loud sounds

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Diary

The subgroup included in this presentation was asked to describe every musical activity during about 2 weeks in terms of duration, type and piece of music. They were specifically asked to answer the following questions:

  1. Which percentage of the time during this activity do you think that the sound was harmful for your hearing (without hearing protectors)?
  2. Which percentage of the time during this activity did you wear hearing protectors?
Dosimetry

The noise dosimeter used was Larson-Davis, type 703 or type 706. It was adjusted to measure the A-weighted sound level using the time constant, "fast," and with a 3-dB exchange rate, according to the regulations in the work environment in Sweden. The subjects were instructed to use it all the time during 2 weeks of their professional musical activities. When possible the microphone was placed on the left shoulder. When that interfered with the use of the instrument, e.g., for violinists and some trombonists, the microphone was placed on the right shoulder.

For each activity noted in the diary, the A-weighted equivalent sound level was calculated, as well as the 20-, 10-, 5-, 2-, and 1-percentiles, i.e., the level that is overridden during the corresponding percentage of time. The measured levels were then compared to the judged percentage of harmful time.

Analyses

The program Statistica 9.1 was used for the statistical analyses. To compare the judged percentage of harmful time with the corresponding sound level a so called logistic function was fitted to the data points for each subject. The function is

T = 100/(1 + exp[(L 50 -L)/S]),

where T is the judged percentage of harmful time, L is the sound level in dB(A), L 50 is the value of L giving T = 50% and S is a slope parameter (the lower value the steeper).

Ethical approval

The study was approved by the Regional Ethical Review Board in Stockholm, Dnr 2008/859-1.


  Results Top


The average total dosimeter time was 41 h per musician. This was somewhat lower than expected, since the dosimeters should be used for 2 working weeks, and from the questionnaire, we found that the mean time that they were exposed to musical sounds as musicians, including education and personal training was 31 h per week. Perhaps they did not use the dosimeter during activities with expected low sound level. The average number of hours during which hearing protectors were used was 7.4 h, i.e., 18%.

The mean number of judged activities per subject was 47, with the range varying from 14 to 76 activities. As much as 30 activities per subject (mean 30, range 7-72) had a judged percentage of harmful time equal to zero.

Four out of the 22 subjects wearing dosimeters judged all their musical activities as harmless, i.e., the judged percentage of harmful time was 0. The total L eq -values from all their activities were 79.7, 85.5, 85.7, and 93.1 dB(A), respectively. They are not included in the further analyses.

For each of the remaining 18 subjects logistic functions were fitted, relating the judgements of percentage of harmless time with the L eq of the corresponding activities. Seven of these subjects were inconsistent in their judgements, resulting in non-significant L 50 - and/or S-values. [Figure 2] shows a scatterplot of all their datapoints. The points above the 0% line are scattered around 90 dB(A).
Figure 2: Scatterplot of all judged activities from seven subjects who made inconsistent judgements of percentage of harmless time, i.e., their fitting parameters L50 and/or S were non‑significant

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Eleven of the subjects had significant L 50 - and S-values, presented in [Table 1]. [Figure 3] and [Figure 4] show examples from two of them, the first tolerating rather loud musical sounds and the second being one of the most susceptible subjects, according to their judgements. They both seemed to be worried about L eq s above 80 dB(A). And in fact their sound level means were not significantly different. However, M055 rated a significantly greater part of the exposure time to be harmful (P < 0.0008, Mann-Whitney U-test). A logistic function for the 11 subjects with significant L 50 - and S-values was obtained by using the arithmetic mean of their L 50 -values and the geometric mean of their S-values [Figure 5].
Figure 3: Scatterplot of all judged activities from a subject (M055) tolerating rather loud sound, who made judgements of percentage of harmless time giving significant fitting parameters L50 and S (100.34; 3.316). The fitted logistic function is also shown

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Figure 4: Scatterplot of all judged activities from a subject (M109) not tolerating loud sound, who made judgments of percentage of harmless time giving significant fitting parameters L50 and S (91.30; 2.825). The fitted logistic function is also shown

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Figure 5: Scatterplot of all judged activities from eleven subjects who made consistent judgments of percentage of harmless time, i.e., their fitting parameters L50 and/or S were significant. A common logistic function is also shown, based on their mean parameters L50 and S shown in the lowest row of Table 1

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Table 1: Significant parameter values L50 and S of the logistic functions adapted to judged values of the eleven musicians who were able to make consistent judgements of perecentage of harmless time. The arithmetic mean value of L50 and the geometric mean value of S are also shown

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In [Table 1] the standard deviation of L 50 is 4.94 dB, which means that the standard error of the mean is 4.94/√11 = 1.5 dB. The confidence interval of L 50 , i.e., the uncertainty of the horizontal position of the curve in [Figure 5], is thus ± 1.5 dB.

The mean value of the responses to the question about the musicians' individual susceptibility to acquire NIHL (response scale in [Figure 1]) was 5.7 (median 6.25), ranging from 1 to 9. This indicates that they regard themselves as sligthly more susceptible to NIHL than normal. This result holds for the total group of 121 subjects in the complete study. The mean value of those who weared dosimeters was 5.6, which was not significantly different from those without dosimeters (mean 5.8).

[Figure 6] shows the percentage use of hearing protectors as a function of equivalent 8 h workday A-weighted sound level exposition for the 22 musicians.
Figure 6: Percentage use of hearing protectors as a function of equivalent 8 h workday A‑weighted sound level exposition for the 22 musicians

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  Discussion Top


Most of the subjects produced a remarkably high number of judgements (mean 47), which could be compared with the sound level of the corresponding activity. Although many of the activities were judged to have 0% harmful time (mean 30 data points per subject), there was a rather large individual variation in the judged values. We don't know how they interpreted the word "harmful" in the diary question, but we got no questions or discussions about that issue when they got the diaries. We assume that they rated the proportion of time when hearing protectors ought to be used.

The subjects did not judge the risk expressed as a percentage figure. Instead, they judged the percentage of time their hearing might be at risk, which we thought would be easier for them since the sound level of the music often fluctuates. However, since we know that the exposure time at a certain sound level is strongly related to the risk according to the "energy principle," it should be possible to compare their judgments with the risk level.

Eleven, i.e., half of the 22 subjects, made judgements that were possible to adapt significantly to a logistic function for which the risk is increasing with the sound level. Even if they seemed to be able to make consistent judgements, we don't know their personal risk, since we have no audiograms before and after the period of judgements. Several years of measurements would also be necessary to obtain significant changes of the hearing losses. However, it can be noted that both the group making consistent judgments [Figure 5] and the group making inconsistent judgments [Figure 2] started to judge the levels to be risky at the lower exposure action value L EX,8h = 80 dB(A) of the European directive. [12]

Two subjects used hearing protectors more than 95% of the dosimeter time, another two just above 50% of the time. The remaining 21 subjects used hearing protectors less than 20% of the dosimeter time. Only four subjects did not use hearing protectors at all. In order to make a choice between using hearing protectors or not, the musicians must have had some knowledge of the natural sound levels of the music pieces that they were going to play and could relate that to the attenuated sound. One may presume that they made valid judgements even in the cases when they used hearing protectors. All the four musicians who used hearing protectors more than 50% of the time [Figure 6] made consistent judgements of the harmfulness.

The participants were asked to use the dosimeter during 2 weeks of work. This corresponds to 41/2 = 20.5 h per week, but from the questionnaire, they reported on average 31 h per week playing, rehearsing, or education. However, in many occasions, they forgot the dosimeter or they forgot to put it on. A couple of them also had less work than usual. According to Laitinen et al. [5] orchestral musicians usually play about 1500 h per annum, i.e., 29 h per week, including their own personal practice time.

Those who are willing to participate in a study like this might be those who regard themselves more susceptible to noise than the general population. The mean result 5.6 of the question shown in [Figure 1] indicates that this might be the case, but we have not tried this question on a normal population. (We just presumed that they would have the result 5.0 on the scale, but we might be wrong.) This fact has to be considered when interpreting the other results of this study.


  Conclusion Top


The results of the present study indicate that half of the participating musicians seemed to be capable to reasonably judge the harmfulness of the music that they were exposed to. However, since many musicians seem not to be able to make such judgements, risk assessments of loud sounds at work should always be based on sound level measurements.


  Acknowledgments Top


The study was supported by grants from AFA Insurance. It was run in the environment of the FAS Centre for Research on Hearing Difficulties in Working Life and Society, supported by the Swedish Council for Working Life and Social Research (2006-1526). Kim Kähäri administered some dosimeter measurements. Sally Allkins and Eva B. Svensson contributed with administration, hearing measurements and data analysis. Ann-Cathrine Lindblad participated in valuable discussions and so did Åke Olofsson, who also provided technical assistance. I wish to express my gratitude to the participating musicians.

 
  References Top

1.Nelson DI, Nelson RY, Concha-Barrientos M, Fingerhut M. The global burden of occupational noise-induced hearing loss. Am J Ind Med 2005;48:446-58.  Back to cited text no. 1
    
2.Behar A, MacDonald E, Lee J, Cui J, Kunov H, Wong W. Noise exposure of music teachers. J Occup Environ Hyg 2004;1:243-7.  Back to cited text no. 2
    
3.Jansson E, Karlsson K. Sound levels recorded within the symphony orchestra and risk criteria for hearing loss. Scand Audiol 1983;12:215-21.  Back to cited text no. 3
    
4.Royster JD, Royster LH, Killion MC. Sound exposures and hearing thresholds of symphony orchestra musicians. J Acoust Soc Am 1991;89:2793-803.  Back to cited text no. 4
    
5.Laitinen HM, Toppila EM, Olkinuora PS, Kuisma K. Sound exposure among the Finnish National Opera personnel. Appl Occup Environ Hyg 2003;18:177-82.  Back to cited text no. 5
    
6.Lee J, Behar A, Kunov H, Wong W. Musicians' noise exposure in orchestra pit. Appl Acoust 2005;66:919-31.  Back to cited text no. 6
    
7.Kähäri K, Zachau G, Eklöf M, Sandsjö L, Möller C. Assessment of hearing and hearing disorders in rock/jazz musicians. Int J Audiol 2003;42:279-88.  Back to cited text no. 7
    
8.Kuwano S, Namba S. Continuous judgment of level-fluctuating sounds and the relationship between overall loudness and instantaneous loudness. Psychol Res 1985;47:27-37.  Back to cited text no. 8
    
9.Dittrich K, Oberfeld D. A comparison of the temporal weighting of annoyance and loudness. J Acoust Soc Am 2009;126:3168-78.  Back to cited text no. 9
    
10.Zwicker E, Fastl H. Loudness. In: Psychoacoustics: Facts and Models. 1 st ed. Berlin: Springer; 1990. p. 181-214.  Back to cited text no. 10
    
11.Gabrielsson A, Hagerman B. Subjective correlates of the acoustical characteristics of sound-reproducing systems. In: Studebaker GA, Hochberg I, editors. Acoustical Factors Affecting Hearing aid Performance. 2 nd ed. Boston: Allyn and Bacon; 1993. p. 310-4.  Back to cited text no. 11
    
12.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). Official Journal of the European Union L42, Brussels, Belgium, 2003. p. 38-44.  Back to cited text no. 12
    

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Correspondence Address:
Björn Hagerman
Starrgränd 31 SE-192 67 Sollentuna
Sweden
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DOI: 10.4103/1463-1741.112376

PMID: 23689304

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
 
 
    Tables

  [Table 1]



 

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