Tinnitus can arise in any of the four sections of the ear: the outer ear, the middle ear, the inner ear, and the brain. Some tinnitus or head noise is normal. If one goes into a soundproof booth and normal outside noise is diminished, one becomes aware of these normal sounds. We are usually not aware of these normal body sounds, because outside noise masks them. Anything, such as wax or a foreign body in the external ear, that blocks these background sounds will cause us to be more aware of our own head sounds. Fluid, infection, or disease of the middle ear bones or ear drum (tympanic membrane) can also cause tinnitus.
One of the most common causes of tinnitus is damage to the microscopic endings of the hearing nerve in the inner ear. Advancing age is generally accompanied by a certain amount of hearing nerve impairment, and consequently tinnitus. Today, loud noise exposure is a very common cause of tinnitus, and it often damages hearing as well.
Unfortunately, many people are unconcerned about the harmful effects of excessively loud noise, firearms and high intensity music. Some medications (for example, aspirin) and other diseases of the inner ear (Ménière's syndrome) can cause tinnitus. Tinnitus can, in very rare situations, be a symptom of such serious problems as an aneurysm or a brain tumor (acoustic tumor).
What is the importance of noise induced hearing loss?
The industrial and technological revolution may have propelled society to higher levels of achievement. At the same time, however, this progress has also made the world a noisier place in which to live. In fact, noise pollution is a growing health hazard and is everywhere.
Car alarms, leaf blowers, gunshots, boom boxes, and traffic congestion fill our cities with decibels (the measure of sound intensity). Even escaping to the country may not provide a quiet refuge. Thus, farmers are at high risk for exposure to noise from their farm machinery.
What's more, potentially harmful noise is not necessarily unpleasant or unwanted. For example, the music at a concert or the pounding of a jackhammer on the street can be equally damaging to the inner ear. The reason for this is that any sounds (acoustic energies) delivered with equal intensity, regardless of their source, are equally dangerous. Eventually, continued or repeated exposures to high intensity sound can cause acoustic trauma to the ear. This trauma can result in hearing loss, ringing in the ears (tinnitus), and occasional dizziness (vertigo), and non-auditory effects, such as increases in heart rate and blood pressure.
Noise remains the most common preventable cause of irreversible sensorineural (involving the ear's sensory nerve) hearing loss.
What are acoustic trauma and noise induced hearing loss?
Acoustic trauma occurs when any excessive sound energy strikes the inner ear. If it is brief, the noise may cause a reversible, temporary auditory fatigue, technically known as a temporary threshold shift. For example, after a loud rock concert, it is common to experience hearing dullness and ringing for several hours. In this situation, if symptoms persist beyond several days, oral steroids (cortisone-type medications) may help the inner ear recover. If the noise is loud enough and the duration of exposure long enough, however, it may cause a permanent threshold shift. This condition is called noise induced hearing loss, and has no cure and is irreversible.
Hearing loss produced by a sudden and very loud noise (blast injury) is called acute acoustic trauma. If the sound is loud enough, it can cause the eardrum to rupture or the person to have a complete loss of hearing. Sometimes, particularly if the sudden loss is total and combined with dizziness, immediate surgical exploration of the ear may be necessary. In this circumstance, the ear surgeon may need to locate and patch a hole (perilymphatic fistula) between the inner ear fluid space and the middle ear space.
How can a person tell if a noisy situation is dangerous to their hearing?
People may differ in their sensitivity to noise. Nevertheless, as a general rule, noise is probably damaging to the hearing if the noise:
Makes it necessary to shout to be heard over the background noise
Causes ear pain
Makes the ears ring
Causes a loss of hearing for several hours or more after exposure to the noise
In contrast to popular belief, there is no truth to the idea that a person is able to "toughen up" the ears by frequent exposure to loud noise. In reality, cumulative noise in the past has probably damaged the ears to such a degree that a person doesn't hear the noise as much. Unfortunately, no treatment is available for noise induced hearing loss once the damage has occurred.
How loud can a sound get before it affects hearing?
Many experts agree that continual exposure to more than 85 decibels (dB) may be dangerous to the ears. As already mentioned, the decibel is a measure of the intensity of sound. The faintest sound the human ear can detect is labeled 0 dB, whereas the noise at a rocket pad during launch approaches 180 dB. A quite whisper is approximately 30 dB, normal conversation is 60 dB, and a lawnmower is 90 dB. Decibels are measured logarithmically, which means that the sound energy of noise increases by units of 10. Therefore, a dB increase of a sound from 20 to 30 dB is an increase of 10 times, and a db increase of a sound from 20 to 40 dB is an increase of 100 times (10 times 10).
Do the duration and closeness of exposure to loud noise relate to hearing damage?
There is a direct correlation between the duration of exposure to a loud noise and the damage to hearing. This means that the longer the exposure, the more the damage. Furthermore, the closer one is to the source of the intense noise, the more damaging it is. For example, a gunshot produces a noise that could damage the ears of anyone in close hearing range. Large bore guns and artillery is the worst because they are the loudest. But even a cap gun or a firecracker can damage the hearing if the explosion is close to the ears. Accordingly, anyone who uses firearms must wear hearing protection.
Studies have shown an alarming increase in hearing loss in children and young adults. Evidence suggests that loud music along with increased use of portable CD players with earphones may be responsible for this increase. Here, the problem is the long duration and close exposure to the loud music.
What factors increase a person's susceptibility to noise induced hearing loss?
The following factors have been associated with an increased susceptibility to noise induced hearing loss:
Blue eyes
Light skin
Family history of hearing loss
Diabetes mellitus
Meniere disease
Iron deficiency
Vitamin A deficiency
Older age
Atherosclerosis (hardening of the arteries)
Smoking tobacco
How else can noise affect a person?
After exposure to noise, tinnitus, which is a ringing or another sound in the ears, occurs commonly. The tinnitus is a sign that inner ear damage or nerve destruction has occurred. Initially the tinnitus will just be temporary, lasting only several hours. As more cumulative exposure and damage occur, the tinnitus will last longer until eventually it will become permanent.
Loud noise will also cause some people to have anxiety and irritability, an increase in heart rate and blood pressure, or an increase in stomach acid. In addition, very loud noise can reduce efficiency in performing difficult tasks by diverting attention from the job.
Do hearing protectors prevent a person from communicating with others?
The answer is no, at least for people with normal hearing. In fact, just as sunglasses help vision in very bright light, hearing protectors enhance speech understanding in very noisy places. Even in a quiet setting, a normal-hearing person wearing hearing protectors should be able to understand a regular conversation.
Hearing protectors do slightly reduce the ability of those with damaged hearing or poor comprehension of language to understand normal conversation. Nevertheless, it is essential that persons with impaired hearing wear earplugs or earmuffs to prevent further inner ear damage from noise.
It has been argued that hearing protectors might reduce a worker's ability to hear the noises that signify an improperly functioning machine. Most workers, however, readily adjust to the quieter sounds and can still detect such problems
How can someone tell if their hearing is already damaged, and what can be done about it?
Hearing loss usually develops over a period of several years. Since the hearing loss is painless and gradual, many people may not notice it. What someone may notice is tinnitus, which is a ringing or another sound in the ear. The tinnitus could be the result of long-term exposure to noise that has damaged the hearing nerve. Or, a person may have trouble understanding what people are saying or may hear everyone as mumbling. Such hearing difficulties are especially apt to occur when one is trying to hear in a noisy place such as in a crowd or at a party. These difficulties could be the beginning of high-frequency hearing loss.
A typical hearing test (audiogram) of a person with noise induced hearing loss will initially show only a high frequency loss at 4000 Hz. (Hertz or Hz is the measure of sound frequency or pitch. Four thousand Hz is high frequency, while 250 or 500 Hz would be low frequency). With continued noise exposure and hearing loss, the audiogram will show a broader loss to include lower (deeper) frequencies.
Noise induced hearing loss will almost always affect both ears equally, but in some situations, especially with firearm usage, it may be worse in one ear than in the other. For example, firing a rifle tends to injure the ear opposite the side of the trigger finger due to the shadow (blocking the sound) effect of the shooter's head.
