Hearing, noise and your health – The Harmful Effects of Noise
The soothing sounds of crickets in the summertime, the vibrato of the violin in a concerto, the trill of the first bird in the spring; all these delicate noises, if we are lucky, are ones that we take for granted. Yet very few of us realize that one does not have to be deaf to be unable to make sense of these sounds. Whether because of sickness or aging, hearing loss affects a large number of us, but there are several things you can do to prevent it.
The human ear is a delicate instrument subject to the sorts of difficulties that any finely crafted instrument might have — if one part is damaged, it reduces accuracy or possibly destroys the ear’s ability to function. Whether from many years of exposure to noise, brief exposure to loud noise, illness, stress or physical trauma, human hearing can easily deteriorate. There are advancements in medicine which give hope, but not ill the parts of the ear can be replaced if damaged.
For its size, the bat has giant ears which can sense objects through a form of sonar. A bat’s screech bounces off an object and is reflected back to the ear communicating distance, size, and movement, all necessary for an animal which is primarily a night feeder.
The human ear, while not as sensitive or as specialized as a bat’s ear, operates in a similar manner. What we understand as sound is caught by the receptive portion of the ear with its odd whorls and channels. Sound waves are directed into the ear canal, where they bounce off the ear drum. Each frequency is translated into a recognizable sound in the sterile, pressurized inner ear and sent to the auditory nerve, which leads to the brain. It is in the brain that our interpretative and contextual abilities lead to speech recognition or awareness that a plane is flying overhead. Every sound has variations in tone and pitch which indicate to us what has created that sound. It is these variations that help us tell the difference between the same note being played by a bassoon or an electric guitar.
The Outer Ear
The visible part of the outer ear is a fascinating feat of evolutionary engineering. It is a strange shape, and, composed entirely of cartilage, it is known to grow larger as we age. It is peculiar that as we lose our hearing from age and noise exposure, the apparatus that is meant to catch sound waves gets bigger.
The ear canal is lined with hairs and has curves and bends in it. Leading directly to the ear drum, or tympanic membrane, it is usually only about an inch to an inch and a half in length. The ear drum separates the outer ear from the middle ear. It is air-proof and waterproof, preventing all forms of microbes or disease causing agents to enter the body through the ear. This may not be the case if it is perforated. In its normal state, when viewed from the ear canal, the ear drum should be barely concave and relaxed enough to vibrate when sound hits it. One of the signs of otitis media, or middle ear infection, is a protruding and taut ear drum. In this state, hearing is usually impaired because the drum cannot move, or there is fluid behind it.
The Middle Ear
As children, we are fascinated when someone mentions that we have a hammer, an anvil, and even a stirrup in our ears. It is these tiny bones that transmit sound from the outer ear and ear drum to the inner ear. From the ear drum, the hammer (malleus), anvil (incus), and stirrup (stapes), act to transmit sound waves to the cochlea, where the sounds are transformed into nerve signals. Sound hits the drum, it jerks the hammer, which is joined to the stirrup by the anvil. The stirrup is attached to something called the oval window on the cochlea. The movements of the bones shape the way sound is transmitted to the cochlea. The cochlea makes up part of the inner ear and is like a snail shell in shape, which is where it gets its name.
The middle ear is fairly open, exposed to bacteria and viruses. The eustachian tube, surrounded by bone at the top and soft flesh at the bottom, connects it to the back of the throat. When we swallow, the opening at the bottom relaxes. The mucus that lines the eustachian tube neatly deposits any microbes that may enter the middle ear into the throat, where natural digestive processes will destroy them.
When an illness develops in which mucus is produced in large amounts, there is potential for it to block the eustachian tubes, which can lead to ear infection. A child’s eustachian tubes are much shorter than an adult’s and are surrounded mostly by bone, as the soft part has not grown to its full size yet. The size and consistency of their eustachian tubes make them more susceptible to ear infection, though adults are not immune.
The Inner Ear
The inner ear comprises the cochlea, the vestibular and cochlear nerves, and the semi-circular canals. It is like a small, pressurized chamber, and surgery is almost impossible in this region because it would destroy function. There is an even smaller canal which runs the length of the internal side of the cochlea, which contains the hair cells. Hair cells can be destroyed by loud noise or by exposure to light noise over the course of a lifetime.
The sound, which arrives at the cochlea after the middle ear bones transmit it to the oval window, reverberates through the cochlea and the semi-circular canals. Through this process, it is converted to a signal that nerves can read and sent through the vestibular nerve to the hearing portion of the brain.
Typically, harm to hair cells affects hearing in a very specific way: background noise can make it very difficult to hear a speaker, creating the sort of sound that you would hear from within a seashell. Consonants, which fall in the highest range of the human hearing scope, become harder to hear, especially ones which are not voiced, such as “s”, “th”, and “f”.
Feeding Ear Infections
As common an act as feeding your baby can affect how often he or she gets ear infections. Infants’ and toddlers’ eustachian tubes are much shorter than those of adults and, because they are surrounded mostly with bone, are not flexible enough to withstand blockage. As a result, bacteria in food not only can make them sick but can also be introduced to the ear via the throat.
The problems lie mostly in improper bottle-feeding. If the child’s head is not at the correct angle, food itself can flow back into the throat and block the eustachian tube, providing another possibility of ear infection. Poorly sterilized bottles and nipples can introduce bacteria to the middle ear, also leading to infection.
Breast-feeding is the least likely way for infants to get ear infections from mealtime. The milk is generally sterile, especially if the mother is disease-free and careful about what medicines she takes and what she eats. In addition, it is difficult to breast-feed at an improper angle. If breast-feeding is not consistently possible, following these simple guidelines for bottle-feeding from Playtex Nursing System can improve your child’s chances against ear infection:
* Keep your child’s head higher than his body to prevent liquid from flowing into the middle ear, which can cause infections.
* Do not put a child to bed with a bottle. Feeding while a child is on his back can cause ear infections, tooth decay, and even choking.
* Using collapsible, disposable plastic bottle liners can reduce the need for bottle sterilization.
* Thoroughly wash nipples and reusable bottles in warm, soapy liquid.
* Sterilize new bottles and nipples before first use.
* Always wash hands before preparing formula or “express” breast milk.
Tinnitus: The Death of Normalcy?
According to the 1990 census, 7 million Americans suffer from tinnitus, commonly known for its symptomatic ringing, hissing, or buzzing in the ears. The American Tinnitus Association places the number closer to 50 million, 12 million of whom have severe and debilitating tinnitus. Regardless of the number, it is an annoying and disruptive affliction which can cause emotional trauma and confusion in those who have it.
For those who endure severe tinnitus, ringing and noise can be loud and incessant, and life can become unbearable. The condition can interfere with daily activity, such as work or sleep, or the ability to conduct normal relationships. Side effects of severe tinnitus may include mild to severe depression; have been known to induce thoughts of suicide. William Shatner, who played the role of Captain James T. Kirk on the original Star Trek series, is now a spokesperson for the American Tinnitus Association. He has said that the ringing he heard led him to consider death as an alternative.
Tinnitus is one of the first signs of noise-induced hearing loss and is becoming much more common in our society as the generally accepted decibel level rises. Tinnitus now affects several age groups, and it is now evident in more young people than ever before. Baby Boomers, the first generation to grow-up in the rock and roll era, are experiencing tinnitus in huge numbers.
As more people suffer from tinnitus, the call for effective solutions is getting louder. A new method of treating tinnitus has been developed that is drug-free. It is called retraining or habituation and forces the brain to cease hearing the tones emitted by the tinnitus.
The patient wears a device, similar in size and shape to a modern hearing aid, and that emits a tone of a slightly lower volume than the tinnitus. The brain gradually ceases to hear the lesser tone, sometimes over the course of a few to several months, and over a longer time ceases to hear the tinnitus.
Dr. Pawel Jastreboff of the University of Maryland developed the therapy. He based his theory on the premise that problems with hearing can cause an imbalance in the hearing mechanism. Those problems may make the brain pick up sounds that might naturally be there but in most people are inaudible.
For those who have successfully used this method, their lives are not just livable but enjoyable again.
The great drawback is that currently very few audiologists or doctors offer the retraining. Audiologists Dr. Jay Hall and Dr. Ann Byrn of the Vanderbilt Balance and Hearing Center offer of retraining and opened a tinnitus center at Vanderbilt with ear specialist Dr. David Haynes.
Noise And Hearing
Most people are familiar with the notion that loud noise can harm hearing. Famous musicians are not the first to be aware that their hearing can be damaged by extended loud noise. Gunners from various wars came home, often to find that their hearing was impaired slightly or sometimes almost entirely destroyed. Cannons or bomb blasts had even ruptured a few ear drums. The discovery of the hair cell added to the knowledge of how hearing loss could occur, but only recently has it been made public that low levels of noise over long periods of time can deteriorate the hearing.
A single blast from a gun may not make you immediately deaf. But recreational marksmen and hunters who do not wear protective ear gear will notice the effects of repeated use of guns after a short period of time. Police officers, especially urban ones, who must discharge weapons in enclosed spaces, never have the opportunity to don protective gear before doing so. We may assume that such people suffer from hearing loss. People who work in noisy environments, like loud factories, need to understand their right to keep their hearing.
The Occupational Safety and Health Administration (OSHA) has set federal standards which must be obeyed by companies whose products are shipped over state lines; however, many of those do not comply, and there are many more to whom the laws do not apply. In environments whose noise levels are above 90 dB.*, OSHA recommends some hearing protection. George Biddle, executive director of Occupational Hearing Services, says, “OSHA gives guidelines for safe amounts of time in noisy environments unguarded, but I don’t think 100 dB, is the kind of noise you should be exposed to without any protection.”
A Ear Canal
B Tympanic Membrane (Ear Drum)
C Malleus (Hammer)
D Incus (Anvil)
E Stapes (Stirrup)
F Eustachian Tube
G Semicircular canal
I Auditory Nerve
COPYRIGHT 1996 Vegetus Publications
COPYRIGHT 2004 Gale Group