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 Noise
in the work place is responsible for the most prevalent occupational
impairment: hearing loss or permanent deafness.(1)
One occupation at risk to this disability is the disc jockey or DJ.
The nightclub disc jockey's
job consists of playing loud music for an extended period of
time. The music being played is often somewhere around the 100
decibel range, and is directed out towards the dancefloor.
While one song is being played for the audience (for convenience I
will call this song {Song A}), the disc jockey uses a pair of
headphones to listen to yet another song {Song B}, while still paying
attention to Song A.
The object for the DJ is to
attempt to match up the bass beats of Song A with Song B.
This is by using turntables
that feature a pitch controll, allowing the DJ to speed up or slow
down Song B so the bass beats match those of Song A. When the
beats are matched up correctly, the DJ lowers the volume of Song A
while increasing the volume of Song B.
This process is called
"mixing" and allows for a continuous beat to be experienced
by the audience.
One of the main tools that
the DJ uses (besides music, of course) is headphones.
To effectively mix two songs
together, the DJ must be able to hear both songs equally, that is, at
the same volume. As mentioned before, the music being blasted
from the speakers to the audience is somewhere near the 100 dB range,
which means that the volume of the DJ's headphones must also be in
the 100 dB range.
As you may have guessed,
playing music through headphones at this level cannot be all that
entirely healthy for one's ears. Ising et al. measured hearing
losses in a non-representative group of pupils whose ages were
between ten and nineteen years who listened to headphones at varying
duration and intensities. It was predicted that 10% of the
group would have a hearing loss of 10 dB at 4 kHz after five
years. 0.35% of the group was expected to develop hearing
losses at age twenty-five years that would be severe enough to
substantially impair speech intelligibility.(2)
Loth D. et al. suggests that
normal use of headphones, as used with portable cassette or compact
disc players (i.e. walkman type players), even when used within
safety regulations may still cause a temporary decrease in hearing
ability. After listening to both rock and classical music,
twelve normally hearing volunteers were shown to have lost an average
of 5 dB of hearing ability at the 4 and 6 kHz range. This study
also suggested that better headphones are likely to cause a temporary
hearing loss at higher frequencies (frequencies above 8 kHz) (3).
However, another study by Turunen- Rise et al. suggests that the
risk for permanent noise - induced hearing loss from these personal
cassette players is very small for normal hearing conditions. (4)
Exposure to rock music for an
extended period of time may also cause a temporary decrease in
hearing. After a concert, hearing levels were measured in
twenty-two volunteers by Yassi et al.. 81% of the participants
showed a decrease in hearing ability of 10 dB or more 5 to 25 minutes
after music exposure. Of these, 76% demonstrated decreased
hearing ability at 40 to 60 minutes after exposure. (4)
Henderson et al. reported on
the ability of the middle ear muscles to develop a resistance to
noise induced hearing loss. After conditioning one group of
chinchillas to loud low frequency sounds, the group was given a rest
period of five days. The conditioned group and a controll group
were both then exposed to forty eight hours of 106 dB noise. It
was demonstrated that the conditioned groups incurred substantially
less permanent hearing loss than the controll group. (5,6)
The way to lower the risk to
a disc jockey for hearing loss is in the setup of equipment. A
normal disc jockey workstation or "booth" consists of
stereo equipment which allows the disc jockey to monitor more than
one song at a time. To do this, a musical loudspeaker is placed
inside the DJ booth which allows the DJ to clearly hear the music
that is playing. This speaker adds to the intensity of the
sound already coming from the dancefloor. If the DJ could lower
the volume of this in-booth speaker (called the monitor) he would not
have to increase his headphone volume as much.
The problem with turning down
the music is that the nightclub is a business where loud music is
supposed to be played. Placing a pillow in front of your
dancefloor speakers to limit the sounds being emitted would
essentially defeat the purpose of playing the music in the first
place. But still, the DJ needs to lower the volume that he is
exposed to.
While examining the
workstation at a nightclub where the author is employed as a disc
jockey, I came up with a few suggestions: First, the DJ booth
should be positioned behind the main dancefloor speakers.
Simply put, it is not as noisy behind a speaker as it is in front of
it. Next, the DJ booth ideally should be enclosed in a sound
proof box, which would cut much of the sound coming from the
dancefloor to the DJ. The DJ could still monitor the sound
level on the dancefloor by the indicator lights on his mixer board,
and he could check the sound quality by using his speaker monitor
that would be placed inside the soundproof box with the
DJ. Because the DJ would no longer have to overcome the
loud music being played from the dancefloor, his in-booth music level
could be cut down, allowing for his headphone level to be lowered.
While earplugs have been
shown to decrease the risk for hearing damage to individuals exposed
to high intensity impulses (7), they would not
be as effective to the DJ because they tend to dampen the low
frequency noises. To a DJ, the low frequency noises are
essential to mix two songs together, and wearing earplugs would
result in a decrease in job efficiency and quality (songs would not
mix together well, beats would not match up correctly because the DJ
couldn't hear the bass clearly, thus resulting in a very bad-sounding
mix called a "train wreck".)
Another mode of hearing loss
prevention to the disc jockey involves a nutritional component.
Correlations were observed between serum magnesium levels and noise
induced permanent hearing threshold shifts. Three hundred
young, healthy and normal hearing recruits all underwent two months
of basic military training which involved repeated exposures to high
levels of impulse noises. These subjects were involved in a
placebo - controlled, double-blind study in which each subject
received daily an additional drink containing 167 mg of magnesium
aspartate or a similar quantity of placebo (Na-aspartate).
Results showed that noise induced permanent threshold shifts were
significantly more frequent in the placebo group than in the
magnesium group. Long term intake of a small dose of oral
magnesium was not accompanied by any notable side effect.
(8)
This study may introduce a significant natural agent for the
reduction of hearing damages for the disc jockey.
In conclusion, the disc
jockey is at a risk for hearing losses. Due to the nature of
the DJ's job, simply turning down the volume at the nightclub is an
unrealistic measure of prevention for noise-induced hearing
loss. While earplugs may be beneficial for others who work in
noise related occupations to lower the risk of hearing damage, they
serve as an obstacle for disc jockey performance. A well
thought out DJ booth and dancefloor seems to be one of the best ways
to reduce hazardous noise levels to the disc jockey.
Nutritionally, oral magnesium
also proves beneficial. While the DJ may adapt to the constant
high levels of music, there should be an effort made by the nightclub
owners, sound system designers, and disc jockeys themselves to limit
the risk of hearing loss to the disc jockey.
Pete Ladd
Kodiax@aol.com
Chiropractor / Disc Jockey
REFERENCES
1.Encyclopedia
of Occupational Health and Safety. 2v. International
Labour Office, 3d ed., 1983.
2.Ising
H, Hanel J, Pilgram M, Babisch W, Lindthammer
A. Risk of hearing loss caused by listening to music with head phones.
HNO 1994; 42
(12) :764-8,
3.Loth D,
Avan P, Menguy C, Teyssou M. Secondary auditory
risks from listening to portable digital compact disc players.
Bulletin de l Academie Nationale de Medecine 1992 Nov;
176(8) :1245-52; discussion 1252-3
4.Turunen-Rise
I, Flottorp G, Tvete O. A study of acquiring
noise-induced hearing loss by the use of personal casette players
(walkman). Scandinavian Audiology 1991; 34:133-44
5.Henderson
D, Subramaniam M, Papazian M, Spongr VP. The
role of middle ear muscles in the development of resistance to noise
induced hearing loss. Hearing Research 1994 Apr;
74(1 - 2) :22-8
6.Subramaniam
M, Henderson D, Spongr VP. Protection from noise
induced hearing loss: is prolonged 'conditioning' necessary?
Hearing
Research 1993 Feb; 65(1 - 2):234-9
7.Dnacer
A, Grateau P. Cabanis A, Barnabe G, Cagnin
G, Vaillant T, Lafont D. Effectiveness of earplugs in
high-intensity impulse noise. Journal of the Acoustical Society
of American. 1992 Mar. 91 (3)
:1677-89
8.Attias
J, Weisz G, Almog S, Shahar A, Wiener M,
Joachims Z, Netzer A, Ising H, Rebentisch E,
Guenther T. Oral magnesium intake reduces permanent hearing
loss by noise exposure. American Journal of Otolaryngology
1994 Jan-Feb; 15(1) :26-32
9.Microsoft
Encarta - 1993 (CD-ROM)
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