Noise exposure of musicians of a ballet orchestra
Cheng Liang Qian1,2, Alberto Behar2, Willy Wong1,2
Edward Rogers Sr. Department of Electrical and Computer Engineering, 2Institute of Biomaterials and Biomedical Engineering,
University of Toronto, Canada
1
Abstract
With over 70 dancers and its own orchestra, The National Ballet of Canada ranks amongst the world’s top dance
companies. It performs three seasons annually: fall, winter and summer, plus many shows of Tchaikovsky’s Nutcracker.
The 70-strong orchestra plays an average of 360 hours/year including rehearsals and performances. Rehearsals are
held at two locations: one in a ballet rehearsal room with little or no absorption, and the other in an acoustically treated
location. Performances are held in the Four Seasons Centre for the Performing Arts in Toronto. The present survey was
done at the request of the National Ballet, since the musicians complained of excessive sound levels and were concerned
about possible hearing losses. The survey was performed using five dosimeters Quest Mod 300 during 10 performances
of the ballet Romeo and Juliet by Sergei Prokofiev, deemed as the noisiest in the whole repertoire. Results of the survey
indicate that the noise exposure levels from only the orchestra’s activities do not present risk of hearing loss. Exposure
due to other musical activities was, however, not included.
Keywords: Noise exposure, dosimetry, field measurement, musician, orchestra
Introduction
Musicians at the National Ballet of Canada’s orchestra were
concerned about the high noise levels they were exposed to
during performances and rehearsals. To assess the actual noise
exposure and the risk of hearing loss, the management requested
a study to be performed by the Sensory Communications
Group at the University of Toronto. The Group has already
performed two similar studies in the past on musicians from
the Canadian Opera Company[1,2] and through these studies has
an established measurement methodology.
The present study consisted in the measurement and
assessment of noise exposure of musicians during 10
performances of Sergei Prokofiev’s “Romeo and Juliet” – a
particularly loud 3-hour ballet. This composition requires
a relatively large, 70 player orchestra. Furthermore, the
noise levels in the orchestra pit may be higher compared
to an open symphonic stage, where symphonic orchestra
performances and rehearsals typically take place. The
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higher levels are due to the enclosed space that increases the
reverberant energy of the sound. The measurements are best
representative of a pit musician’s noise exposures during
actual live performances.
Noise-induced hearing loss is the result of long exposures to
high sound levels. Measurements of those levels are performed
using noise dosimeters that integrate the noise levels for the
entire duration of the event. The result is shown as Leq,t. 1Leq,t
is the equivalent noise level during the time t, obtained using
a 3 dB exchange rate
When a measurement is performed for a duration different
than 8 hours, the result has to be converted to the equivalent
8-hour exposure Leq,8 using the formula
Leq,8 = Leq,t + 10 log(t/8)dBA
(1)
where t is the actual measurement duration (hours).
Musicians at the National Ballet Company perform for 360
hours/year, as opposed to the usual 2000 hours/year (8 hours/
day) in the case of workers in other industry. For 2000 hours,
Equation (1) becomes
Leq,8 = Leq + 10 log(t/2000)dBA
(2)
Using t = 360 hours, Equation (2) becomes
Leq,8 = Leq – 7.4dBA
(3)
Noise & Health, January-February 2011, 13:50,59-63
Qian, et al.: Noise exposure of musicians of a ballet orchestra
Measurements
Measurement Procedures
Measurements were performed during 10 performances of
the ballet “Romeo and Juliet” by Prokofiev. All performances
were held at the Four Seasons Centre for the Performing Arts.
Inaugurated in 2006, this is the first theater in Canada built
specifically for opera and ballet. Presently, it is considered as
one of the finest halls in the world.
Approximately 15 minutes before the start of a performance,
each designated musician was fitted with a dosimeter.
The operator in charge of the test attached personally the
microphone of the dosimeter to the collar of the musician
(according to the instrument played, it was attached either
to the left or the right side of the musician’s body). Then,
the microphone cable was fixed to the back of the musician.
This was done to avoid interfering with the musician’s
performance, or creating a potential safety hazard.
Measuring Instruments
Five Quest Q-300 dosimeters were used during each
performance. They were set to measure Leq following the
guidelines in CSA Standard Z107.56-94.[3] Instruments
were set up and calibrated in our laboratory using the
manufacturer’s QuestSuite Application software.
Dosimeter Locations
The set-up consisted of dosimeters, each with a cabled
microphone. Each dosimeter was clipped to the musician’s
belt, with the microphone attached to the collar or shoulder
seam of the musician’s shirt on the side chosen by the player.
In the case of shoulder-borne instruments such as the violin,
the microphone was attached to the right shoulder of the
player.
Since only five dosimeters were used, it was intended
that the number of tests per instrument be approximately
proportional to the number of players of this instrument. In
addition, certain musicians were measured in more than one
performance. Nevertheless, an even spatial coverage of the
orchestra pit was achieved.
Table 1 shows the total number of players for each instrument
and the number of separate measurements performed on
players of this group.
Table 1: Number of tests performed during the study
Instruments
Violin 1
Violin 2
Violas
Cellos
Basses
Flutes
Oboe
Clarinets
Bassoons
Trumpets
Horns
Trombones
Tuba
Percussion
Total
No. of players
1
9
7
7
4
3
3
4
3
4
6
3
1
4
69
No. of tests
5
5
6
6
3
3
2
3
3
2
3
3
1
5
50
Noise & Health, January-February 2011, Volume 13
The operator further kept a record of the following: the name
of each of the five musicians tested on that particular day,
their instruments, their locations on the floor plan and the
start and end time of the testing.
At the end of the performance, the operator followed the
procedure of stopping the data collection, disconnecting the
microphone, removing the dosimeter from the musician and
recording the measured Leq from the dosimeter.
Measurement Results
Table 2 summarizes the results of the noise exposure
measurements performed on the different musicians. All
results are Leq,3 (dBA), i.e., the actual reading on each of the
dosimeters after each performance.
It can be seen that the numbers of measurements for the
different musician groups vary between 2 and 6. As mentioned
earlier, some musicians wore the dosimeters for more than
one session. This was done to investigate the variation in Leq,3
across different performances. These particular results are
underlined in the table.
Table 2: Measurement results
Instrument
Measured Leq,3
Mean Leq,3a
1st violin
2nd violin
Viola
Cello
Double bass
Flute
Oboe
Clarinet
Bassoon
Trumpet
French horn
Trombone
Tuba
Percussion
86.9 87.2b 88.2 86.3 85.6
84.2 86.8 84.7 83.8 91.3c
84.9 84.9 85.7 87.8 86.5 89.1d
87.3 86.1 87.0 86.9 86.6 88.2
88.8 90.3 90.9
94.1 92.8 91.6
88.5 87.9
88.6 90.6 88.5
88.0 89.6 88.0
94.2 94.2
91.2 90.8 92.2
93.4 93.7 92.4
91.8
90.4 88.3 87.6 87.3 88.5
87
87
87
87
90
93
88
89
89
94
91
93
92
89
Values rounded up to the nearest integer; bUnderlined values indicate measurements
repeated on same individual; cThis player was positioned next to the grand-piano,
set at half-stand (see Figure 1 and discussion); dThis viola player wore dosimeter’s
microphone once on the shoulder (first measurement) and once on a headband
pointing down at their instrument
a
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Qian, et al.: Noise exposure of musicians of a ballet orchestra
Figure 1: Instruments location in the orchestra pit
The mean Leq,3 shown in the last column of the table
corresponds to the energetic average of the measured values
given by Equation (4).
eq ,3i
1 N
mean Leq.3 = 10 log  ∑ 10
N i
L
/ 10



(4)
Figure 1 below represents the floor plan and the seating
distribution of the players within the pit. A few of the
musicians are located under an acoustically transparent
overhang that is used as a safety net to stop objects (and even
dancers) from falling into the pit. The end of the overhang is
indicated by the curved line on the figure.
Discussion
Variations of noise exposures in the orchestra pit
The variations of the noise exposure of musicians in the
orchestra pit can be attributed to a combination of factors.
These include the sound power of the instrument the
musician is playing, of the instruments in the vicinity, the
time variation aspects of the music, and of sound reflections
from the limiting surfaces.
A comparison of the sound exposure from different instruments
is presented in Figure 2. Instruments are grouped by their
location within the pit and ordered from lowest to highest
mean sound exposure. The woodwinds are separated into flutes
and the remaining woodwinds, as there was a significant (P <
0.001) difference in measured sound exposure levels between
these subgroups. Since the string sections were also separated
spatially [Figure 1], sections were divided into three subgroups:
a) violins, b) viola and cello, and c) double bass. There were
significant (P < 0.01) noise exposure level differences between
double bass and all other string instruments.
Furthermore, there was a surprising statistical difference
(P < 0.05) between the sound level of the 1st violins and 2nd
violin section even though these two sections are composed
of the same instruments, located adjacent to each other. This
difference may be best explained by the fact that the 1st violins
were seated next to the pit wall, and were thus subjected to
61
Figure 2: Leq min, mean [see Equation (3)] and max of various
instrument sections as grouped by location. Sections are ordered
from lowest to highest mean sound exposures
additional exposure from reflections from the nearby wall.
This highlights the potential difference in sound exposure
between pit orchestra and stage orchestra musicians.
Variability within same instrument group and same
musicians
To estimate the variability within the same instrument and
musician across multiple performances, a few musicians
were measured more than once. In general, these repeated
measurements yielded very similar Leq results (see underlined
entries in Table 2). With the exception of one viola player
and percussionist, the measurements were within 2 dB of
one another, a difference well within measurement error. The
data support the idea that professional orchestras are quite
consistent (in terms of sound level at least) across several
performances of the same work. This can also be inferred
from the relative consistency (also within 2 dB range)
of measurements within each instrument section when
measured across performances. For future assessments, this
suggests that a few measurements per instrument section
can adequately characterize sound exposure over several
performances of the same piece.
The larger variability of sound exposure measured on
the percussionist and viola player are easily explained.
Percussionists, unlike other orchestra musicians, move quite
dynamically between several different locations (playing
several percussion instruments) during the performance,
adding extra variability.
One viola player represented an interesting case that
illustrates the impact of the location of the dosimeter
microphone. He was measured twice, first with the dosimeter
microphone on the shoulder opposite their instrument. For
the next measurement, he decided to wear the microphone
on a headband pointing down at their viola. This yielded
measurements of 86.5 and 89.1 dBA, respectively, with a
difference representing roughly a doubling of the sound
energy. This suggests that future studies should consider
Noise & Health, January-February 2011, Volume 13
Qian, et al.: Noise exposure of musicians of a ballet orchestra
making creative efforts to measure on the side of the body
exposed to the higher levels, to obtain more conservative
estimate of the sound exposure.
Are these musicians at risk of hearing loss?
The most important question addressed in the study is
whether musicians are at increased risk of hearing loss after
years of performance in orchestra pits. We used the ISO
1999:1990 threshold shift algorithm[4] to predict the noiseinduced permanent threshold shift (NIPTS) expected in an
individual musician as a function of the exposure level (in
Leq,8) and their percentile susceptibility to hearing damage.
Though performances in the orchestra pit only occupy a
portion of a musician’s time, they likely constitute the highest
exposure levels due to the sheer number of instruments being
played nearby. To arrive at a reasonable Leq,8 from the Leq,3
measured during performance, two additional assumptions
must be made. Firstly, it is assumed that this piece of music
is representative of the typical sound levels of performances.
Prokofiev’s “Romeo and Juliet” is actually one of the loudest
performances of ballet music, and so assessing general risk
based on this piece may lead to erroneous conclusions. The
second assumption is that other activities such as practice,
other performances and/or teaching do not contribute
significantly to the total level of exposure, relative to the
exposure from performances. This may not be a fully valid
assumption and cannot be easily verified without continuous
dosimeter measurement of a musician throughout their daily
activities. Musicians themselves need to be conscious of
any other activities that might significantly increase their
exposure, such as teaching group music classes.
To compute Leq,8, the measured Leq needs to be adjusted [using
Equation (2)] by −7.4 dB corresponding to 300 hours of
performance compared to the 2000 hours of work assumed
by Leq,8. After this adjustment, the Leq,8 of several instrument
groups fall immediately to below 80 dBA, which is widely
considered as presenting minimal risk. Two instrument
groups, brass and flutes/piccolos, have higher exposures
with mean Leq,8 of 85.4 and 85.6 dBA, respectively. For these
players, the projected hearing loss (after a 40-year career in
performance) due to exposure alone is calculated using the
ISO1999:1990 algorithm[4] and is presented in Figure 3. It
is easy to see that under the assumptions of this calculation,
even the musicians in this group who have the highest
vulnerability to noise are only expected to experience mild
shifts (<10 dB) in hearing threshold.
However, since hearing is typically more important to
musicians than other individuals, musicians may still wish to
Noise & Health, January-February 2011, Volume 13
Figure 3: Noise-Induced Permanent Threshold Shift (NIPTS)
projections of musicians (playing brasses and flutes) measured
at 93 dBA (Leq,8 = 85 dBA), after performing for 40 years. Each
curve represents predictions for a different percentile resistance
to hearing damage. For example, 50 percentile is the median and
90 percentile means top 10% resistance. All threshold shifts are
mild and <10 dB even for the most susceptible part population
reduce the risk of hearing loss. To this end, a reduction of 5
dB in sound exposure to approximately the same level as the
remainder of the orchestra will minimize the risk for brass
and flute players such that the predicted NIPTS is <3 dB.
Some recommendations on providing this amount of noise
exposure reduction are presented in Appendix-A.
Conclusion
The present work was an assessment of pit orchestra musicians’
risk of noise-induced hearing loss. We have highlighted
several considerations for proper and efficient assessment of
orchestra-related sound exposure, including the fact that the
accuracy of the noise exposure measurement is within ±2
dB.The measurements done over one particularly loud ballet
piece (Prokofiev’s “Romeo and Juliet”) indicate that musicians
of the National Ballet of Canada Orchestra are, in general, not
overexposed due to performances alone. The conservative
assumption in this study was that the measured noise exposure
applies to all orchestral activities of the musicians, including
rehearsals and playing other pieces, while it actually represents
the noisiest activity they are likely to partake in.
Address for correspondence:
Mr. Cheng Liang Qian,
1317-438 King St. West.
Toronto, ON, Canada.
E-mail: chengliang.qian@utoronto.ca
62
Qian, et al.: Noise exposure of musicians of a ballet orchestra
Appendix-A
Noise exposure controls for musicians
Controls should be instituted whenever noise exposure levels are at or above safe limits. There are basically three types of controls: engineering,
administrative and use of personal protective equipment.
Engineering noise controls
These should be considered as the first option. In the case of musicians in an orchestra, especially those seated in front of the wind instruments, there have
been many attempts to implement engineering controls. The preferred approach has been installing barriers, more often behind the backs of the musician
seated in front of the wind instruments. However, they have had very limited success. One of the reasons is the need that barriers be optically transparent so
that the view of the musician is not impaired. This requirement limits the choice to the use of non-absorbent, highly reflective materials such as Plexiglas and
similar. Being reflective, they increase the sound level generated by the instrument and received by the player. Also, to be effective, barriers have to be large,
something not acceptable in a relatively small orchestra pit.
Wind instruments are highly directional. Placing them higher than the rest of the musicians appears to improve the situation. This is the reason for the moderate
success of the use of risers. However, this solution, usual in symphonic orchestra, tends to be unsuitable in the pit because of the relatively low ceiling.
In an enclosed space, the use of sound absorbing material covering the exposed surfaces reduces the reflected sound energy and consequently can reduce
the sound levels. This solution can hardly be applied in the pit. The ceiling is already highly absorptive (being partially open to the hall). Also, the relatively
high density of the musicians increases significantly the total absorption. Only in case of musicians situated next to the walls of the pit (such as the outside 1st
violinists), the use of sound absorbing material may reduce their noise exposure level.
Administrative control measures
They consist of reducing the duration of the exposure. In the present case, this will imply shorter playing times, something which is difficult to apply to
musicians in an orchestra due to the requirements of their occupation. Alternatively, when it is feasible from a repertoire planning point of view, it may be
worthwhile to balance a repertoire with louder and quieter performances to give musicians some recovery time.
Use of personal protective equipment
This is the only remaining exposure control, and the one that is easier to apply in theory. Unfortunately, musicians are reluctant to the use of protectors. The
three most often quoted reasons are:
a) lack of comfort,
b) occlusion effect (when using plugs), and
c) distortion of the perceived sound due to increasing attenuation of high frequencies.
There is no single solution at the present time for the lack of comfort – this is a general complaint from users of every kind of personal protective equipment
(PPE), such as hard hats, respirators, etc. Earplugs with custom-fitted ear molds do offer some degree of comfort by ensuring good fit. However, ear canals
do change with aging and fit cannot be guaranteed after a number of years.
The occlusion effect occurs when an object fills the outer portion of a person's ear canal. This person perceives "hollow" or "booming" echo-like sounds of
his/her own voice. This effect can only be reduced by inserting the plugs deep in the ear canal, something that reduces the level of comfort even further.
The sound attenuation of most hearing protectors is proportional to the frequency – there is higher attenuation at higher frequencies. The net result is that the
music is perceived as “muffled” or lacking in clarity. This problem is resolved by the use of protectors known as “Fidelity” or “Musician” earplugs that have
flat attenuations across the frequency range. Another advantage of these devices is that their attenuation is usually low to moderate (10–25 dB). Musicians
do not need large attenuation since the noise exposure levels are not too high. Furthermore, some earplugs, particularly those with custom ear molds, include
an interchangeable flat-attenuation filter which allows the musician to configure for the desired total attenuation. This allows a means of compensating for
the difference between rehearsal and performance sound levels by switching between different filters. Hence, flat-attenuation ear plugs appear to be the most
practical solution for reducing sound exposure of musicians.
Players have to accept the relative lack of comfort and adapt to the sound of their instruments and the orchestra while wearing hearing protectors. This
is especially important for musicians who play in loud instrument sections, in more than one orchestra, or teach playing to large groups. Players must
themselves consciously consider the balance between the inconvenience associated with protection, and the risk of hearing loss.
References
1. Lee J, Behar A, Kunov H, Wong W. Musicians’ noise exposure in
orchestra pit. Applied Acoustics 2005;66:919-31.
2. MacDonald E, Behar A, Wong W, Kunov H. Noise Exposure of
Orchestra Musicians. Canadian Acoustics 2008;36:11-6.
63
3. CSA Standard Z107.56-06. Procedures for the measurement of
occupational noise exposure. Canadian Standards Association; 2006.
4. ISO Standard 1999:1990. Acoustics – Determination of occupational
noise exposure and estimation of noise-induced hearing impairment.
International Organization for Standardization; 1999.
Source of Support: Nil, Conflict of Interest: None declared.
Noise & Health, January-February 2011, Volume 13