People who study acoustics define noise as complex sound waves that are aperiodic, in other words, sound waves with irregular vibrations and no definite pitch.
In engineering, noise is defined as a signal that interferes with the detection of or quality of another signal.
The combined disciplines of psychology and acoustics (psychoacoustics) study the response of humans to sound. They define noise as unwanted sound.
Is music noise? Is the hum of tires on a highway noise? Is the surround-sound movie theater noise? Is the philharmonic concert noise? And what about the accompanying beat for aerobic exercises at the health club? Sounds that are soothing for some are irritating to others.
An expert on noise, K.D. Kryter (1996) in his text , Handbook of Hearing and the Effects of Noise, (New York Academic Press) defined noise as "acoustic signals which can negatively affect the physiological or psychological well-being of an individual."
Basically, noise is unwanted sound. It is a pollutant and a hazard to human health and hearing. In fact, to me it is the most pervasive pollutant in Vietnam.
Noise in our environment affects physical heath. Noise also has psychological and social implications and affects our well being and quality of life. Let's add the damage it will cause to musician and engineer alike.
Damage to the Inner Ear
Your ear receives sound waves and sends them through a delicately balanced system to the brain. Part of this remarkable system, the cochlea, is a chamber in the inner ear filled with fluid and lined with thousands of tiny hair cells. The hair cells signal the auditory nerve to send electrical impulses to the brain. The brain interprets these impulses as sound. When you are exposed to loud or prolonged noise, the hair cells are damaged and the transmission of sound is permanently altered.
Noise Levels
Both the amount of noise and the length of time you are exposed to the noise determine its ability to damage your hearing. Noise levels are measured in decibels (dB). The higher the decibel level, the louder the noise. Sounds louder than 80 decibels (normal conversation is at 65 decibels) are considered potentially hazardous. The noise chart below gives an idea of average decibel levels for everyday sounds around you.
Painful:
150 dB = rock music peak
140 dB = firearms, air raid siren, jet engine
130 dB = jackhammer
120 dB = jet plane take-off, amplified rock music at 4-6 ft., car stereo,
band practice
Extremely loud:
110 dB = rock music, model airplane
106 dB = timpani and bass drum rolls
100 dB = snowmobile, chain saw, pneumatic drill
90 dB = lawnmower, shop tools, truck traffic, subway
Very loud:
80 dB = alarm clock, busy street
Note: check this out, I measure the noise level in the mid afternoon in Vietnam and the meter on my SPL meter is licking the 90 dB...that is crazy!
70 dB = busy traffic, vacuum cleaner
60 dB = conversation, dishwasher
Moderate:
50 dB = moderate rainfall
40 dB = quiet room
Faint:
30 dB = whisper, quiet library
Warning Signs of Hazardous Noise
- You must raise your voice to be heard
- You can't hear someone two feet away from you
- Speech around you sounds muffled or dull after leaving a noise area
- You have pain or ringing on your ears (tinnitus) after exposure to noise.
Hazardous Noise
Sounds louder than 80 decibels are considered potentially dangerous. Both the amount of noise and the length of time of exposure determine the amount of damage. Hair cells of the inner ear and the hearing nerve can be damaged by an intense brief impulse, like an explosion, or by continuous and/or repeated exposure to noise.
Examples of noise levels considered dangerous by experts are a lawnmower, a rock concert, firearms, firecrackers, headset listening systems, motorcycles, tractors, household appliances (garbage disposals, blenders, food processors/choppers, etc.) and noisy toys. All can deliver sound over 90 decibels and some up to 140 decibels.
Can't my ears "adjust" and "get used" to regular noise?
If you think you have "gotten used to" the noise you are routinely exposed to, then most likely you have already suffered damage and have acquired a permanent hearing loss. Don't be fooled by thinking your ears are "tough" or that you have the ability to "tune it out"! Noise induced hearing loss is usually gradual and painless, but, unfortunately, permanent. Once destroyed, the hearing nerve and its sensory nerve cells do not regenerate!
An audiologist certified by the American Speech-Language-Hearing Association (ASHA) can conduct a hearing evaluation to determine if you do have a hearing loss. If you are routinely exposed to noise, you should have your hearing checked by an ASHA-certified audiologist on a regular basis, at least once a year.
To me this is one of the most dangerous situation in 'noisy' Vietnam, especially for young infants and children.
Physical Changes
The most notable physical effect of noise exposure is loss of hearing . Noise Induced Hearing Loss (NIHL) affects children, adolescents, young adults, and older adults. The National Institute on Deafness and Other Communication Disorders (NIDCD), National Institutes of Health (NIH) the National Institute on Environmental Health Sciences (NIEHS) and the National Institute for Occupational Safety and Health (NIOSH) have noted that, because of noise in our society, hearing loss is appearing much earlier in life than would have been expected just 30 years ago.
Noise not only affects hearing. It affects other parts of the body and body systems . It is now known that noise:
- Increases blood pressure
- Has negative cardiovascular effects such as changing the way the heart beats
- Increases breathing rate
- Disturbs digestion
- Can cause an upset stomach or ulcer
- Can negatively impact a developing fetus, perhaps contributing to premature birth
- Makes it difficult to sleep, even after the noise stops
- Intensifies the effects of factors like drugs, alcohol, aging and carbon monoxide
Research is on-going and continues to provide data suggesting the devastating effects of noise on health. Research is also investigating factors that may contribute to one's susceptibility to noise induced hearing loss.
Other Changes
Noise can also hamper performance of daily tasks, increase fatigue, and cause irritability.
Noise can reduce efficiency in performing daily tasks by reducing attention to tasks. This is a concern of employers when it comes to assuring workers' safety. It is also a concern to a growing number of educators interested in human learning.
Because of noise, we often find ourselves fatigued and irritable . We don't even realize the effect until the noisy hubbub stops and we feel relief.
From another perspective, your own inability to hear and understand others clearly can cause you to feel angry and frustrated. Instead of accepting the problem is yours, you misdirect your feelings to others and blow up at them.
Noise also makes speech communication harder. More concentration and energy is needed not only to listen and hear over the noise but also to speak louder above the noise. As a result, voices can be strained and vocal cord abuses, such as laryngitis, develop. It is a physical strain to carry on even an enjoyable conversation in the presence of noise.
One demonstration of the effects of noise on behavior was done by recording how passers-by responded to a person-in-need in the presence of noise. While a noisy lawnmower was running, a woman with a broken arm dropped some books and tried to pick them up. No one stopped to help her. When the lawnmower was turned off and the scene repeated, several people stopped to help her retrieve the books.
Researchers have also looked at the effect of excessive noise in school classrooms and have drawn conclusions that are seemingly obvious, yet often minimized. In one study, test results of students from a school near railroad tracks were compared to results of students far away from the tracks. Students in the quiet school performed better on the test. Another study found that students whose classrooms face noisy streets do not do as well in school as students in classrooms facing away from noisy streets. Finally, another study demonstrated that noise distracts both teachers and students.
There is no question that noise is both a public health hazard and an environmental pollutant as well. Many of its effects are well known and many of its effects continue to unfold through research.
Protect Yourself from Noise
The key word in dealing with noise is prevention! We want to eliminate unwanted noise when we can. When noise cannot be eliminated, we want to keep it as low as possible. Here are some things to do:
- Wear hearing protectors when exposed to any loud or potentially damaging noise at work, in the community (heavy traffic, rock concerts, hunting, etc.) or at home . Cotton in your ears won't work.
Hearing protectors include ear muffs and ear plugs (not swimmer's plugs), some that are custom-made and individually molded. This protection can be purchased at drug stores, sporting goods stores or can be custom-made.
The dam thing come with its own sub mounted side way
