How does the ear work?
Any source of sound sends vibrations or sound waves into the air. These funnels through the ear opening, down the ear canal, and strike the eardrum, causing it to vibrate. The vibrations are passed to the bones in the middle ear, which transmits the vibrations to the auditory hair cells in the inner ear. There, the vibrations are transmitted to the brain, which interprets the vibrations as sound: music, a voice, a slamming door, etc.
When noise is too loud, it may kill the hair cells in the inner ear. As the exposure time and/or the loudness increases, more and more hair cells are destroyed. As the number of hair cells decrease, so does your hearing. There is no way to restore life to dead hair cells; the damage is irreversible.
What is loudness?
Sound originates when a body moves back and forth (like the conus of a loudspeaker), causing a travelling sound wave by alternately compressing the air and then relaxing the compression. The loudness of a sound is related to the level of compression and so the resulting pressure level of the sound wave.
Sound is measured in decibels [dB]. When it is corrected to the perception of the human ear, the level is indicated as dB(A). The scale runs from the faintest sound the human ear can detect; "0 dB(A)" to over 180 dB(A), the noise at a rocket pad during launch.
Decibels are measured logarithmically. This means that as the dB number increases by 10, the sound intensity increase is 10 times.
What is frequency?
The pitch of a sound is related to the number of pressure changes (cycles) per second, and expressed in Hertz [Hz]. The human ear is capable of detecting sound waves with frequencies between about 20 Hz (the lowest note on a large pipe organ), to 20,000 Hz such as the high shrill of a dog whistle that many people are unable to hear. However, the ear is most sensitive to sound waves in the range between 1,000 and 6,000 Hz.
When does noise become dangerous?
People differ in their sensitivity to noise. As a general rule, noise may damage your hearing if you have to shout over background noise to make yourself heard. If so, the level will be approximately 80 dB(A) or more. The higher the level the more damaging it will be. Very loud sounds of short duration, such as an explosion or gunfire, is usual painful and can produce immediate severe and permanent hearing loss.
But exposure to noise levels between 80 and 120 dB can "painless" cause hearing damage - damage that you may not be aware of at the time, but will notice when it is done and too late. The longer the exposure time, the more damage may be caused.
What if my hearing is already damaged? How can I tell?
Hearing loss usually develops over a period of years. Since it is painless and gradual, you might not notice it. Signs of damage are; when the noise hurts your ears, makes your ears ring, or when you feel slightly deaf for some time after exposure to the noise.
Hearing impairment associated with noise exposure can occur at any age. It is notified by difficulty in understanding what people say; they may seem to be mumbling, especially when you are in a noisy place such as at a party. And the potentially troublesome symptom; tinnitus, a 'continues' ringing sound in the ear. This could mean the beginning of more severe hearing loss; a hearing test will detect it. But you may as well have nothing more serious than impacted wax or an ear infection, which can be simply corrected. However, it might be hearing loss.
In any case, take no chances with noise. If you suspect hearing loss, consult a physician. This doctor can diagnose your hearing problem and recommend the best way to manage it.
Can noise affect more than my hearing?
Some people react to noise with anxiety, fatigue, irritability, an increase in pulse rate and blood pressure, or an increase in stomach acid. Noise also can affect efficiency in performing difficult tasks by reduced concentration.
Can I "toughen up" my ears?
No, if you think you have grown used to a loud noise, it probably has damaged your ears and there is NO treatment - NO medicine - ANY surgery, not even a hearing aid that truly corrects your hearing once it is damaged by noise.
What sources can be dangerous?
Sources mentioned below produce an excessive sound level, which may cause hearing damage:
Disco / Rock concert 110 dB(A)
Circular saw 105 dB(A)
Sporting event 100 dB(A)
Motorcyclist (at 90 km/h) 95 dB(A)
Average Factory Noise 90 dB(A)
Loud party 85 dB(A)
Airplane cabin 80 dB(A)
What is a safe exposure time?
Sooner than one realizes, our hearing is over exposed to dangerous noise levels, as can be seen in thetable below:
Level of noise in dB(A) Safe "daily" exposure time
80 8 hours
86 2 hours
92 30 minutes
98 7 minutes
How to prevent hearing damage?
If you (have or want to) stay in an excessive noisy environment, you should always wear hearing protectors. Hearing protectors decrease the intensity of sound that reaches the eardrum and will so prevent noise induced hearing loss. There are many types available and a proper selection is very important.
When making your choice keep in mind: "the best hearing protector is the protector which is actual worn".
Hearing protectors are available in two main forms: earmuffs and earplugs.
enclose the ear shell and are sealed to the head by soft cushions. A tensioning (head) band providing the necessary sealing force connects the cups.
Quick and easy donning and removal, direct available and fits everybody, no interference with auditory canal problems, good high frequency attenuation.
Inconvenient load on, and pressure to the head, very uncomfortable at higher temperatures, loss of "directional hearing" (localization of the sound source).
Earplugs are worn in, or cover the auditory ear canal to seal the entrance against noise.
Earplugs can be divided into three main groups; disposable, pre-shaped and custom moulded.
are made of polymer foam material and shaped into a thin roll before insertion into the ear canal. After insertion the foam will return to its original dimension and so seal the ear canal. They are intended for single use only. Correct (deep) insertion is essential for adequate noise insulation.
Pre-shaped earplugs are inserted directly into, or covering the entrance of the auditory canal. They can be re-used several times and are washable. Also for these, correct (if possibly deep) insertion is essential for adequate noise insulation.
Advantages (disposable and pre-shaped)
Direct available and fits most of the users,
No inconvenience load on / or pressure to the head,
No discomfort in warm environment,
Directional hearing is not affected.
Disadvantages (disposable and pre-shaped)
Level of protection very dependent from accurate fitting
Good training is needed, come loose slowly, so regular re-fitting is needed and important for adequate protection,
Discomfort due to pressure in the ear canal when fitted correctly,
Limited choice in attenuation levels.
Custom moulded earplugs are made-to-measure to the individual's external auditory ear canal. The plug provides the sealing to the canal, while an additional acoustic filter determines the attenuation required.
Advantages from ELACIN otoplastics/custom moulded earplugs
(in addition to disposable and pre-shaped)
Maximal wearing comfort especially for long term use,
Easy, safe and unambiguous to fit, stable (form) fitting providing a high level of protection
Availability of filters to suit the best level of attenuation and signal and sound perception, continuous ventilationof the ear canal.
Not directly available (delivery time),
Relatively high investment at the time of introduction, but cost effective in time