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The capacity of the human hearing system to absorb sounds of different intensities is astounding. If the appropriate acoustic conditions are given, we can perceive minimal sounds such as our own blood flow, an experience which many people may have had, as it is the rushing sound of our blood circulation which is heard when we cover our ears with a seashell. What is happening here is that by completely blocking external noise, internal sounds become audible. On the opposite extreme, some people are capable of withstanding -and even enjoying- overwhelming sounds, like those in a rock concert.
These are two extreme situations which, potentially, the human hearing system can deal with. In numeric terms, the sound impact of a rock concert is one billion (a million millions) times more intense than that generated by blood circulation. Daily, people are astounded by contemporary technological developments but, how much more should they be surprised if they were aware of the real potential of their senses?
There is no humanly created instrument which comes near to the wonder that is the hearing system. The ear's capacity for dealing with different sound intensities is so ample that it has been necessary to use mathematical representations. That is why it is frequent to hear -or read- about decibels of sound pressure. It is a relative logarithmic scale which transforms the gigantic million millions into 120 dB SPL (sound pressure decibels). On this scale, the sound of blood flow corresponds to 0 dB SPL and that of a rock concert to 120 dB SPL.
Other eloquent examples of sound intensities heard daily around the world: a conversation held a normal levels occurs at 70 dB SPL, which means that it is 10 million times more intense that the sound produced by blood flow. A street with intense traffic makes about 80 dB SPL, which is 10 times louder than a conversation with little loudness, whereas a shout from a short distance measures 100 dB SPL, one thousand times more than a normal chat. SPLs can be easily measured with a sound pressure meters easily availabe at any RadioShack store.
What matters is always to remember that the hearing system is a natural jewel perfectly designed, but not as robust as to withstand the loudness of the modern world without being seriously affected. The functioning of the hearing organ is more precise than that of the best clock in the world, and, for example, as a consequence of the sound potentially produced by the movement of the molecules of the air that we breathe, the internal membrane of the ear moves one-tenth of the diameter of a hydrogen atom.
When it is pressured by highly intense sounds for a relatively long time, the hearing apparatus is permanently damaged beyond the possibility of natural or medical restoration. Precisely in order to protect humanity from the dangers of excessive noise, the European Community elaborated a chart which specifies maximum innocuous exposure and formulated an alert: beyond the maximum lengths of time indicated, irreparable damage is produced to the system.
Whoever has been to a nightclub and noticed that is necessary to shout to be able to communicate must be aware that they are being exposed to around 100 dB SPL, and a review of the nightclubs of Montevideo shows that in the majority the noise is well above that level. This means that -in the best of cases- you should only stay inside them for no longer than 30 minutes. Unless the patron does not care to see his/her ears permanently damaged.
In the same way, whoever wishes to attend a rock concert should recall that the amount of time considered innocuous for his/her hearing apparatus is reduced to only 28 seconds. Unfortunately nature did not consider the type of use that humans would put their hearing to at the end of the 20th century. Without awareness of these risks, young people risk beginning the next century with their hearing potential almost detroyed.
Townshead suffers from acute deafness and a disease called tinitus, an illness for which no cure has yet been found -despite that it is common among people who do not take care of their hearing- and is characterized by the sufferer constantly hearing non-existent noises and humming. The dramatic reality is that this musician will never again hear the sound of silence.
The chart elaborated by the European Comminuty reveals that nobody is safe from damage to their hearing, as this not only depends on the intensity of the sounds but also on the duration of exposure. There are noisy workplaces -above 90 dB SPL- which are responsible for irreparable damages when lingered in for more than 8 hours a day.
European specialists claim that the levels on the chart are conservative, and the European Community is about to establish a maximum of 85 dB SPL for an 8-hour workplace. More stringent norms will reduce exposure times by almost four times. Dentists and taxi-drivers integrate some of the high-risk groups.
Humans are aware of the adaptive potential of their sight. They know that when a person is surrounded by the darkness of night the bright light of an approaching car causes discomfort, but on the other hand, the same car lights would remain unnoticed during a sunny day. What many people may not be aware of is that hearing is also adaptable to different sound intensities, but this capacity makes the issue of intense noises more problematic.
For many young people no volume is enough, since once they become adapted to loudness they do not sense it as such and they feel a need to increase even more the sound pressure that they are being exposed to. A similar situation occurs with some diskjockeys who constantly increase the potency of their equipment causing increasingly serious damages in the hearing of their public.
Nobody waits to see a doctor when they notice a mininal failing of their sight, yet they only consult an ear specialist when their hearing deterioration has become serious. It is important to remember that all sound exposure above allowed limits destroys parts of the delicate capillary cells of the internal ear, which are the ones responsible for sending auditive information to the brain. In extreme cases -such as unfortunate people affected by an explosion- the damage may be sudden and is known as auditive trauma. In the more common cases (excessive exposure to SPL for longer than appropriate times) the damage is produced gradually.
This process of cellular death makes it difficult to realize the degree of damage that is being suffered, which increases the need to become aware of the problem. It is a sad case to begin to take care once you have discovered that you cannot understand what people are saying or to have to ask them to repeat themselves several times. Nonetheless, it is never late to protect one's hearing.
Society should demand that norms of universal respect be obeyed -such as those recommended by the European Community- to guarantee the auditive health of the population, since, like all ideals, universalization is a process which will necessarily take time. Until then, people should grow in awareness and impose self-control. There is a measure which can be taken on an individual basis and does not imply any drastic change in lifestyle: the use of comfortable sponge plugs which reduce sound pressure by some considerable 29 dB SPL. By wearing them, a rock concert will have an auditive impact of 91 dB SPL on the spectator, by which s/he may enjoy the music for almost 8 hours without endangering his/her hearing.
In a fashionable nightclub in Europe and the U.S.A. is it common to see young people using these plugs, and it can be expected that the fashion will soon follow in other parts of the world.
If someone feels embarrassed to use sponges in their ears, they should consider if it will not be more frustrating -and make them the victim of mock and discrimination- to pretend to understand what they cannot hear because they are deaf.
Life offers infinite beauty perceivable through all of our senses. Just one of them which shuts down is a part of the world closing in on us. The act of being, the development of consciousness, spiritual growth, and attention to what is real, rests on the full joy of odors, touching, tasting, seeing and hearing. This is the fire of existence, the certainty that living is a true pleasure.
The world is improved with positive additions. In times of crises, the senses can only reformulate existence if they remain open. Every incident which blunts them is a step backwards. A prematurely deaf youth will have difficulty in constructing a magic world, above all if one is aware that before entering the battle for a newer and happier order, one must possess the degree of poetry which is aquired by hearing a distant and simple raindrop.