HEARING IMPAIRMENT DUE TO NOISE AND LOUD
SOUND REPRODUCTION
SOME NEW POINTS OF VIEW AND SOME HYPOTHESES
FOR FURTHER
RESEARCH
©1983 The Anstendig Institute
Fine
music, at normal to soft volume levels, is capable of physically calming and
refining the -listener's body while producing internal physical experiences of
an emotional nature that can range from exquisite to frightening. But music is
also capable of strongly stimulating the body to movement and of determining
the character of the movements, in which case, the louder the music, the
stronger the effect. This, of course, is what people are after when they go to
dance at discos where music is played at nearly ear-splitting volume levels.
There are certain very real experiences to be had from loud volume listening,
but loud volume levels also present very real dangers to one's hearing.
I.
SOUND IS A STRONG, MEASURABLE PHYSICAL FORCE
It
is generally wrongly assumed that the experience of hearing is principally a
non-physical matter of conscious experience and that the accompanying emotions
also occur in the non-physical realm of consciousness. But, hearing is
primarily a physical phenomenon: up until the very last stage, in which the
physical, material phenomena of vibrations are somehow transformed into the
non-physical, immaterial phenomenon of consciousness, all stages of hearing are
physical in nature. (The mental processing of what one hears is no longer part
of the act of hearing, but necessarily a process that follows it.) It is seldom
realized that sound waves themselves are strong physical forces. But consider
the fact that, in many microphones, the pickup element would be demolished by
volume levels that are still within the tolerances of human hearing and that
special microphones have to be built to withstand the force of much loud rock
music. Clearly, sound waves have considerable force. The physical force of
sound, coupled with our deeply ingrained psychological reactions to it, make
sound probably the most powerful influence on us. To understand this, think of
your reactions to a car's screeching brakes, to a policeman's siren, to an
explosion, to someone crying, etc. Only intense pain might cause stronger, but
not faster, reactions.
II.
THERE IS REASON TO BELIEVE THE LOUDNESS OF SOUND IS NOT THE ONLY FACTOR THAT
LEADS TO HEARING LOSS
The
problem of hearing loss due to noise or due to listening to music is generally
considered to be exclusively a matter of how loud the sounds are, the
assumption being that soft sounds are less dangerous and loud sounds more
dangerous. In fact, many articles on the problem of hearing loss describe fixed
volume levels beyond or within which any sounds will cause hearing impairment,
and these limits are not very loud (one well-publicized claim is that exposure
to sounds of 70 to 80 do for long periods of time will result in hearing
damage, and the ranges of 90 to 110 do are described as dangerous even for
short periods). While The Anstendig Institute does not doubt these findings, it
has reason to believe that, at such comparatively moderate volume levels, the
loudness of the sounds per se is not the main reason for hearing loss. The
evidence we cite is that:
1)
in The Anstendig Institute's own test-situations, we have been able to observe
just the opposite result, i.e., greater hearing sensitivity after long sessions
of listening to music that was within the stated volume ranges;
2)
we know of other situations that produce the same effect of greater hearing
sensitivity after people are subjected to even louder volume levels. For
example: orchestras routinely use rehearsal rooms that are just big enough to
house their 100 or so members, and we have never heard of anyone suffering
hearing impairment from a good rehearsal. In fact, a phenomenon often happens
whereby everyone is hearing MORE acutely after a first-class rehearsal. This is
noticeable in the fact that, beforehand, when everyone has arrived and taken his
seat, the ambient noises in the room are not noticed. But afterwards, and even
during pauses later in the rehearsal, the ambient noise is annoyingly apparent.
Suddenly everyone notices every little sound, most of which were present before
the rehearsal. Obviously the hearing of those in the room has changed so that
everyone is hearing louder due to the physical relaxation and acute
concentration necessary in order to play their instruments. A heightened state
of sensitivity has resulted and not a hearing loss, even though, under these
conditions, sound pressure levels of well over 100 dB are common. I spent many
summers rehearsing daily in orchestras and bands numbering well over 200
players in the Interlochen Bowl of the National Music
Camp,
Long
before the present public awareness of the dangers of loud volume listening,
The Anstendig Institute conducted test sessions in which long tapes of music
having the same equalization characteristics were played. The listening was
begun at a moderate volume level and the music was correctly equalized to sound
natural at that level. The volume was then slowly increased until sound
pressure levels of 100 dB to 115 dB occurred momentarily at climaxes. Each
successive increase in volume was carefully re-equalized to retain the same
natural sounding quality. At the end of these sessions, everyone present was
invariably hearing louder and more perceptively. Room sounds, like the hum of
the amplifier's power supply, the residual noise coming through the speakers,
street noises, every tiniest movement by anyone in the room, were suddenly
disturbingly loud whereas, before the session, no one noticed them. One could
literally hear a pin drop. It was obvious to everyone that this was due the deeper
state of relaxation of muscle-tensions their bodies had relaxed into while
listening. That became clear when we disturbed the physical state we were in by
getting up and doing other things that demanded the tensions of our usual
bodily movements and reactions: some of the acuity of our hearing had been lost
when we then returned to listening, but everyone noticed that they were still
hearing louder than before we listened to the loud music.
Incidentally,
we have observed that the above improvements in sensitivity in hearing will
usually be accompanied by an added sensitivity in the other senses, i.e., one
tastes more intensely, one smells more intensely, etc. The Anstendig Institute
strongly recommends that the medical-research community investigate this
interrelation of all sensory perception by accompanying tests of hearing loss
with tests of other sensory perceptions. It would be interesting to test
whether loud sounds and music which cause damage to people's hearing also cause
a diminished sensitivity in other areas of sensory perception.
The
above examples should not be misunderstood as claiming that the dangers of loud
music and loud noise have been exaggerated. The hearing losses that have been
observed are very real and scientifically well documented, and there is no
reason to doubt the audiologists' warning that the problem is reaching epidemic
proportions. The above examples merely indicate that there is much more to the
problem than currently indicated and that, at volume levels that are within
known human tolerances (up to short term peaks of 110 dB to 115 dB--the threshold
of pain is 140 dB) not ALL loud sounds are damaging. Some can, under the right
conditions, be beneficial. But most people cannot adequately differentiate
between dangerous and not-dangerous sounds, so it must be emphasized that one
should, as a rule, avoid all unnecessarily loud sounds.
Obviously,
music played by an orchestra in a rehearsal and the music used in The Anstendig
Institute's tests differ greatly from the usual sounds that we are bombarded
with in our everyday lives. Musical sounds are not merely noise. They are, in
the case of the rehearsal room, relatively refined sounds produced live by
those present in the room, whose bodies are vibrating in the same vibrational
flow of the music they are playing. The recorded music used by the Institute
has been screened by Mr. Anstendig, a trained orchestra conductor. Only music
played in the most refined manner possible, both in its expressiveness and in
its rhythmic flow, is used. Of utmost importance is the fact that the music is
equalized by Mr. Anstendig so that it sounds natural and that the equalization
is readjusted for every change in the overall volume level.
Our
tests indicate that one can be hearing louder and more sensitively after
relaxed listening at louder volume levels (85 to 100 dB, with momentary peaks
above 100 dB) IF THE PERFORMANCE IS OF HIGHEST QUALITY, IF THE SOUND
REPRODUCTION HAS BEEN CAREFULLY EQUALIZED WHILE LISTENING, AND
IF THE LISTENER REMAINS RELAXED AFTERWARDS. This phenomenon is not, however,
limited only to listening at loud volume levels. The same phenomenon of
increased sensitivity can occur when listening to music at moderate levels. The
Anstendig Institute also observes this in its more typical test sessions during
which the music remains mostly within 60 to 80 dB volume levels, with peaks of
about 90 to 95 dB.
The
conclusion is that being subjected to 70-80 dB of noise is probably
dangerous only because of the ERRATIC quality of the noise, not because
of the volume level. Finest music at those volume levels would have the
opposite effect.
III.
THE QUALITY OF SOUNDS PLAYS A GREAT ROLE IN THEIR EFFECT ON US
The music that we listen to can affect us in a positive or
negative manner depending on the quality of the music and, more particularly,
the quality of the performance. The composers of most classical
masterpieces have carefully considered their intended expressive content in
relation to the technical possibilities of instruments or the voice. These
masterpieces "sit" well, i.e., are comfortable to play, only when
played in the manner presupposed by the composer, which means with the intended
expressive content. In wrongly interpreted, or just plain badly played,
performances, there is an added factor of unease and discomfort for the
players. The performances do not flow naturally, the rhythmic quality suffers,
becoming especially erratic at every awkward-to-play passage, and the
uneasiness of the players becomes part of the expressive content, usually
dominating it. The playing either becomes nervously keyed up, usually when the
music is difficult to play, or it becomes lethargic,
bored, and enervated when the players have no technical difficulty but the
performance is not "happening" expressively. The Anstendig Institute
is aware of recordings by highly respected musicians that key listeners up and
make them nervous and physically uncomfortable, to the point of causing
hyperactive physical effects such as diarrhea in very sensitive subjects.
Similarly, we have had experience with recordings of music that create just the
opposite state in the listener--one of lethargy, diffuse concentration, and
ennui. We have not documented the effect of these performances on one's
hearing, because they are either stopped as soon as we become aware of their
effect, or they are played for relatively short periods of time, either to
corroborate our observations or to demonstrate them. But because of the effect
produced on our bodies, we strongly suspect that these types of
less-than-impeccably performed recordings play the greatest role in hearing
loss from listening to recordings, especially when the volume level stays below
100 dB. This supposition strongly supports our conclusion that, with low
volume-level noise, it is the ERRATIC quality of the noise that is
responsible for hearing damage.
Many
of the negative effects on people that are attributed to noise pollution could
very well be due to the erratic nature of the other vibrational influences
around them. This is especially likely when negative effects are apparently due
to noise levels as low as 70 to 80 dB, as have been reported. Most noise of the
70 to 80 dB level comes from sources that also produce other vibrations besides
sound vibrations. At that relatively low sound-pressure level, the effects of
other erratic vibrations, especially in one's immediate surroundings, could
easily have more effect on a person than the sounds. A very possible effect is
that the sounds and the other (usually mechanical) vibrations could be
vibrating at rhythmic dissonance to each other,
thereby causing ill-effects on one's hearing mechanism. For example, our paper Hearing
Loss From Listening with Headphones suggests that the bodies of people
listening with headphones are often out of synchronization with the program
they are listening to due to erratic or otherwise coarser vibrational
influences around them. This dissonance between their bodies and the listening
program can amount to a physical irritation. Parts of the structure of the ear
are so delicate that this irritation could be causing subtle damage, especially
to the most delicately vibrating sections of the inner ear that have to simulate
the very highest and lowest frequencies that are more difficult to produce
because of the fast speed in the one case and the slow speed and the magnitude
of the wave-length in the other. Since the person listening with headphones is
distracted by what is being listened to and since this damage would affect
frequencies that are usually not the fundamental sounds, he would not
necessarily notice either the irritation due to the erratic influences around
him or their effects. He would experience both as part of the listening
experience in the same way that the listener does not notice the effects of
overly loud volume levels while he is listening to them. We refer the reader to
our papers on the quality and the effects on us of the vibrational influences
around us.
IV.
EQUALIZATION CAN REDUCE THE DANGERS OF LOUD RECORDINGS
Since
some people will insist on playing recordings loudly, measures should be taken
to minimize the chance of damage. We are more sensitive to some frequencies
than others and this characteristic of our hearing worsens at loud volume
levels. Also, in amplified live music and in sound-reproduction there are
exaggerated peaks in volume at approximately the same frequency range to which
we are most sensitive. Much of the damage done by loud-volume listening is due
to the peaks in volume in those frequency ranges. But all amplified sound
reproduction has to be equalized in order for it to sound natural. Those
frequencies that have to be reduced the most in volume in order for sound-reproduction
to sound natural at loud volume levels are exactly the frequencies to which we
are most sensitive. Therefore, when music is properly equalized, it can be
played at substantially louder volume levels--loud enough to satisfy most
loud-music fans-with greatly reduced danger of hearing damage.
It
should be emphasized that the program-equalization under discussion is
different from the type of equalization sometimes used in the audio industry.
Usually the audio-industry uses equalizers to smooth out the frequency response
of a sound-system in a given room with the help of measuring instruments. That
type of equalization is called room-equalization. What The Anstendig Institute
means by PROGRAM-equalization is the equalization by ear of the program material
while it is playing so that it sounds natural to the listener. Essentially,
this amounts to using an equalizer as an elaborate tone-control. When done
correctly (with a little practice) this type of equalization will automatically
compensate for the greater sensitivities of the listeners in the most dangerous
frequency ranges.
The
instruments mostly used for measuring volume levels of sound are called
Sound-Pressure-Level-Meters. These meters give a reading that reflects an average
of the volume of all the frequencies. But sounds are never equally loud in all
frequencies, and in fact, are usually of highly uneven loudness,
with certain frequencies often many times louder than others (these are called
peaks). Thus, one should not rely on sound-pressure-level-meters to set a limit
to the volume of sounds as their readings do not give any indication of the
volume of these frequency peaks which could easily be 20 dB or more louder than
the reading on the meter. This fact makes reference to "tolerable"
sound-pressure-levels a highly inaccurate designation.
Our
research shows that our hearing is not a fixed entity, but changes in
sensitivity over relatively short periods of time, particularly in relation to
our physical states of tension and relaxation.2 The greatest amount
of change in the shortest period of time has been observed during concentrated
music-listening as the subject's body relaxes into and is affected by the flow
of the music. We also found that the degree of change in sensitivity is not equal
in all frequency ranges. The frequencies where the most change occurs are in
the regions where much hearing loss occurs. This fact makes the testing of a
person's hearing very similar to attempts to study the brain in relation to
consciousness. In order to study it, one has to disturb or destroy it: one
cannot get inside and look at the brain without destroying it and even external
means of studying it disturb or destroy the phenomena of consciousness that one
wants to study. For example, one can never study the brain's functioning during
an exquisite artistic experience because the means of studying it, no matter
how sophisticated, can never be as delicate as the experience and would have to
coarsen, if not destroy, it. Similarly, testing a person's hearing when the
person is anything less than totally comfortable in his/her most characteristic
listening attitude in sympathetic surroundings can never duplicate that
person's actual hearing acuity. Even the weight of wearing headphones or visual
distractions can disturb a person's natural potential for auditory perceptions.
The subject must be given time to relax and become comfortable in his/her
surroundings and the testing must be done in situations that do not entail
distractions or physically uncomfortable apparatus.
The
observations and suggestions in this paper may seem too subtle to be factors in
tangible damage to one's hearing. But one must remember that, along with sight,
hearing is the most complicated and most delicate process known to man. The whole
being plays a role in the hearing experience since it involves the whole body--
not just the hearing apparatus centered around our
ears--and all capacities of mind. We do not hear the source of a sound; we hear
the vibrations of our own bodies after they are caused to vibrate by the
sound-waves from the source. Sound vibrations have to be recreated by our
bodies before we experience them. Sound waves are small to begin with, and the
reproduction of them by the body takes place in miniature, particularly in the
tiny, innermost parts of the ear. The enormous effects on us that hearing
sounds, even quiet ones, can have indicates that these tiny components of the
hearing mechanism are interconnected with all of the networks of the body that
cause our reactions. Most hearing impairment is not an equal reduction in
volume of all frequencies, but rather involves specific frequencies that are
physically difficult for our bodies to reproduce such as the low bass or the
high frequencies. In view of the extreme delicacy of most of the hearing
process and the fact that the body has to be able to reproduce the vibrations
in all their nuances in order for us to hear and experience them, it becomes
easy to understand that the slightest imbalances, unnecessary tensions,
irritations, and even conflicting vibrations can derange the hearing mechanism
enough to limit one's ability to physically reproduce, and thus to hear and
experience, some of the finer frequency ranges and expressive nuances. Hearing
consists in hearing sounds and in perceiving the characteristics of and the
nuances in the flow of the sounds. When hearing, the body is
much like a phonograph needle in a record groove in that it must trace and
recreate all the vibrations, nuances, and qualities of vibrations around it.
Nuance is as important as loudness in a complete listening experience, and The
Anstendig Institute recommends including tests of sensitivity to nuance in
auditory testing.
1 Related papers of The
Anstendig Institute point out that we are affected physically by the quality of
all external vibrational influences around us. The
reasons for this are explained in the paper “The Body as a Machine”.
2
See our paper “Sound Equalization In Relation To How We Perceive
Sound”.
The
Anstendig Institute is a non-profit, tax-exempt, research institute that was
founded to investigate the vibrational influences in our lives and to pursue
research in the fields of sight and sound; to provide material designed to help
the public become aware of and understand vibrational influences; to instruct
the public in how to improve the quality of those influences in their lives;
and to provide the research and explanations that are necessary for an
understanding of how we see and hear.