After reading this essay you will learn about:- 1. Definition of Noise Pollution 2. Nature of Noise Pollution 3. Effect of Noise Pollution on Humans 4. Sources 5. Ways to Reduce 6. Psychological Effects.
Essay # Definition of Noise Pollution:
In the scientific parlance, noise (or sound) is a pressure oscillation in the air, water or any medium that radiates away from the source, Noise or sound is energy, where there is a high sound level and there is a high-energy involvement. Hence, if noise can be controlled at a source, there is a saving in energy and saving in energy costs, which will impact on production.
Pollution from legal point of view, is generally speaking the wrongful contamination of the atmosphere, or of water, or of soil, to the material injury of the right of an individual. Thus, noise as pollutant produces contaminated environment that becomes a nuisance and affects the health of a person, his activities and mental abilities.
Encyclopedia Americana defines it as:
Noise by definition is unwanted sound. What is pleasant to some ears may be extremely unpleasant to others, depending on a number of psychological factors. The sweetest music, if it disturbs a person who is trying to concentrate or to sleep, is a noise to him, just as the sound of a pneumatic riveting hammer is noise to nearly everyone.
So Noise Pollution may be defined as an unwanted sound which gets dumped into the atmosphere without regard to the adverse effect it may be having.
Noise is a disturbance to the human environment that is escalating at such a high rate that it will become a major threat to the quality of human lives. In the past thirty years, noise in all areas, especially in urban areas, have been increasing rapidly. There are numerous effects on the human environment due to the increase in noise pollution.
Noise has been a form of air pollution and like other forms of pollution it affects the quality of life and so can be thought as a social cost. Noise distracts, annoys, disturbs, and when exposed for a long-time, noise can also cause physiological effects leading to deafness.
Essay # Nature of Noise Pollution:
In acoustics noise is defined as any undesired sound. Usually, noise is a mixture of many tones combined in a non-musical manner.
If we treat sound as an auditory sensation produced by these vibrating bodies, its pitch, loudness and tone quality characterizes it.
When an object serves as a source of sound; the pitch is determined by how rapidly the object vibrates. The rate of vibration is called the frequency. The higher the frequency, the higher the pitch, and lower the frequency, lower the pitch.
A change in the pitch occurs as one moves rapidly towards or away from the source of the sound, as when a train-rider approaches or leaves a railway crossing signal, the lower pitch caused by “stretching out” the sound waves, or the reverse effect produced by “squeezing together” the sound waves, is called the Doppler Effect.
It may be regarded as a measure of these pressure variations.
Anything that vibrates has a frequency, has a vibration. The greater the energy that goes into producing the sound, the greater the amplitude of the sound that is produced.
The disturbance spreads outwards from the source and when the pressure variations reach our eardrum they are translated by hearing mechanism into the sensation we call it a sound.
Loudness is defined as the observer’s auditory impression of the strength of a sound. It is a subjective impression related to the intensity components of the sound, and is different in concept from other abstraction such as noisiness and annoyance.
Essay # Effect of Noise Pollution on Humans:
Almost everyone has had one experience of being temporarily “deafened” by a loud noise. This “deafness” in not permanent, although it is often accompanied by a ringing in the ears, and one can hear another person if he raises his voice. Likewise, normal hearing comes back within a few hours at the most.
This sort of partial hearing loss is called Temporary Threshold Shift (TTS). A TTS may be experienced after firing a gun or after a long drive in a car with the windows open. It may not be considered that if exposure to this type of loud noise at a rate of eight hours a day, five days a week can/is a threat to develop permanent hearing loss.
This type of exposure to noise does not have to be as loud as a gun being fired; it can be as simple as a person shouting across the room. The type of hearing loss is any degree from partial to complete hearing loss. This loss, usually, is permanent and is not satisfactorily corrected by any devices such as, hearing aids.
The loss is caused by the destruction of the delicate hair cells and their auditory nerve connections in the Organ of Corti, which is contained in the cochlea. Every exposure to loud noise destroys some cells, but prolonged exposure damages a larger amount of cells, and ultimately collapses the Organ of Corti, which causes deafness.
There are two types of hearing loss: conductive and sensorineural. In conductive deafness sound-pressure waves never reach the cochlea, most often as a consequence of a ruptured eardrum or a defect in the ossicles of the middle ear.
The three bones form a system of levers linked together, hammer pushing anvil, anvil-pushing stirrup. Working together, the bones amplify the force of sound vibrations. Taken together, the bones double, often treble the force of the vibrations reaching the eardrum.
Mitigation of potentially harmful amplification occurs via muscles of the middle ear. These muscles act as safety device protection for the ear against excessive vibrations from very loud noises, very much like an automatic damper or volume control.
When jarring sounds with their rapid vibrations strike the eardrum; the muscles twist the bones slightly, allowing the stirrup to rotate in a different direction. With this directional shift, less force is transmitted to the inner ear: less, not all.
The human ear is a delicate and fragile anatomical structure on the other hand it’s a fairly powerful physical force. These muscles act quickly but not always as in examples of when the ear catches the sound of gun being shot unexpectedly. The muscles of the ear were relaxed and were unprepared for such a blast, because of this damage was done.
Conductive hearing loss can be minimized, even overcome by use of the familiar hearing aids. The most common is worn over the mastoid bond behind the pinna. It picks up sound waves and transmits them through the skull to the cochlea.
Sensorineural hearing loss, the most common form in the United States, occurs as a result of advancing age as well as exposure to loud noises. In both instances there is a disruption of the organ of Corti. The organ serves two functions: converting mechanical energy to electrical and dispatching to the brain a coded version of the original sound with information about frequency, intensity, and timbre.
The hair cells of the organ of Corti send their electrochemical signals into the central nervous system, where the signals are picked up by thousands of auditory nerve fibres and transmitted to the brain. It is the decoding of all the information that enables a person to distinguish the unique and separate sounds of a violin, trumpet, and clarinet, even all three are playing the same note.
Noise effects on human beings:
1. Permanent hearing loss
2. Neural- Humoral stress response
3. Destruction of artifacts
1. Mental stress
4. Sleep interference
5. Temporary hearing loss
6. Speech interference
Essay # Sources of Noise:
The paper-thin walls in most new apartment buildings are frequently assaulted by the noise from his neighbour’s appliances as well as his own. In some communities, intrusion of noise from nearby industrial areas is a serious problem. But in most of the world’s metropolitan areas construction and transport sources, particularly trucks, motorcycles, cars and aircrafts are the most serious offenders.
Types of sources of Noise:
Sources of noise are numerous but maybe broadly classified into two classes such as:
The industrial may include noises from various industries operating in cities, like, transportation, vehicular movements such as car, motorcycles and aircrafts.
The disturbing qualities of noise emitted by industrial premises are generally its loudness, distinguishing features such as total or impulsive components, and its intermittence and duration.
Among the non-industrial sources, important ones are:
4. Construction works
5. Radios, microphones etc.
In India no function is complete without a loudspeaker which has all the characteristics of a public nuisance. The religious ceremonies and electioneering campaigns use public address systems, which use loudspeakers. Most people bear it and are reluctant to lodge a complaint for the fear of earning the wrath of the noisemakers.
Noises associated with manufacturing, building, construction, street work and road repairs make noises that are second only to transportation noises. Jackhammers compressors and pile drivers often din traffic sound.
Below is the list of all construction equipment and the noise levels they produce:
Since construction noise is usually temporary the effected usually bear it and take it as a cost of development.
Methods for Controlling Noise from Construction:
The best way to reduce construction noise is to prevent it from generation but since developing and maintaining the machines are usually costly, the noise generated is usually chosen over the financial burden.
Some of the ways by which noise production can be controlled, are (a) proper internal design of machinery, (b) proper and regular maintenance and usage during appropriate hours.
But unless the government comes up with proper legislation covering noise production due to construction activities, it is impossible to check and controls this source of noise pollution.
Noise from Industry and its Control:
No environmental factors have caused so much confusion regarding its effect on workers efficiency and workers health as industrial noise.
Noise in industry originate from processes causing impacts, vibration or reciprocatory moments.
Noise emission standards have only an indirect control over the noise radiated by the machine. The maximum permissible sound level at a workers ears and the time of exposure are not related directly to the noise produced by one machine but depend upon the total noise in the area.
The maximum permissible sound levels crossing industrial and construction site boundaries into residential and commercial zones may be stated in terms of over all weighted sound pressure levels or in terms of octave band levels. The Indian Standards Institute has set an upper limit of 90 decibels in establishments, as above that the workers are likely to suffer hearing loss.
Control of Noise from the Industries:
It is essential to find out means to control industrial noise because if the ways and means are known it becomes easy for framing the laws.
Essay # Ways to Reduce Noise Pollution:
1. Co-operation between planners and environmental authorities because when a plan is laid out for further improvement of the city the environmental authority has to O.K. the plans.
2. Noise “free zones” and “noise abatement” zones—the easiest and cheapest way to control noise pollution to certain degree is to form “noise free zones”. Such zones should be made around schools, hospitals and places of worship and these should be enlarged further.
3. Acoustic design criteria one of the first decisions to be made before starting a noise reduction programme on a machine is to establish an acoustic design goal.
4. Noise reduction at source. It is found that by regular and constant maintenance the wear and tear of the machines can be considerably reduced and thus directly decreasing noise levels.
5. Screen the noise levels. Noise levels can be reduced if the source of the noise is screened properly by thick walls and other noise absorbing materials. If a machinery is being operated in an open room it is likely to make more noise than a machine working in the open.
6. Screening the receiver. The use of earplugs and cotton should be encouraged where no other method is possible.
7. Vibration isolation. The vibrating machines should be isolated from the other structures by mounting them on resilient mounts.
8. External design changes. Portable air compressors have been designated as a major noise source by the EPA. It would be a waste of time to try and make internal design changes, because the driving internal combustion engine is a major noise source. The small compressors can be easily adjusted for lower noise levels but the bigger ones have to be isolated and mounted on rubber dampeners to reduce the noise they make.
9. Silencers are generally of two types i) the reactive and ii) the absorptive.
Most reactive silencers for industrial applications have high pass filters, which attenuate low frequency noise only.
The absorptive type of silencer has been basically a section of pipe or duct, which is lined with an absorbent material. Such as mineral wool or glass fibre.
10. Vibration damping:
By sticking a pre-formed sheet of material on to the material, which vibrates the most, the majority of the noise can be reduced.
Road Traffic Noise and Its Control:
Various surveys have shown that road traffic noise is the major cause of noise pollution, this is not a surprise because of the large number of automobile machines compared to other machines.
Also because road transport is usually very cost conscious, the economic condition of the owner has been detrimental in vehicle design and operational methods. Diesel engines operate at a higher combustion rate and thus consume less fuel, meanwhile making more noise.
In Delhi the rapid growth of vehicles from 2.5 lakhs to 6.8 lakhs in the last 10 yrs. has added to noise pollution by a much higher level. The failure to segregate fast and slow moving vehicles has resulted in slowing down and accelerating frequently, thus creating more noise. Traffic noises are of two types i) noise generated by individual vehicles and ii) noise due to the continuous movement of vehicles.
1. Noise from engine and transmission
2. Exhaust noise.
3. Slamming car-doors.
4. Brake squeal.
5. Use of horns.
Luxury limousine Small passenger car Miniature passenger car Sports car
Motorcycle (4-stroke) Motorcycle (2-stroke)
Noise from a Continuous Stream of Vehicles:
It has been found that vehicles make the most noise when accelerating in low gears, thus if the number of starts and stops are reduced the noise levels on the road will be considerably reduced. It can also be by providing by pasts, ring roads and urban motorways help in reducing noise levels. Trees bushes and shrubs along the roads also cut down overall noise levels.
Methods to control road traffic noise:
Although an individual can control the noise of his own vehicle by proper maintenance, usage of the appropriate silencers, and also by keeping noise as a criteria while buying a vehicle, it would also help if a law were framed which illegalizes noise above a certain level. Also local pressure groups and NGO’s can play an important part in keeping the overall noise levels down.
Aircraft and Airport noise:
Aircrafts have been the most dramatic of the man-made noises, which are heard by the general community in the vicinity of the airport. There are many thousands of people living in the vicinity of the airport who are moderately and seriously annoyed by the airport noise. Aircraft noise originates from both the propulsion system and the airframe, of which the noise made by the propulsion system, is the major noise source.
Noise Control as a Systems Concept:
Protection of the public health and welfare from aircraft noise has been accomplished most effectively by exercising four noise control options taken together as a system.
1. Source Control:
Involving the application of the basic design principles or special hardware to the engine-airframe combination, which will minimize the generation and radiation of noise.
2. Path Control:
Involving the application of flight procedures that will minimize the generation and propagation of noise.
3. Receiver Control:
Involving the application of procedures such as restriction on the type and use of aircraft at the airport, which will minimize community noise exposure.
4. Land use Control:
Involving the development or modification of airport surroundings for maximum noise compatible usage.
Noise from trains and It’s Control:
The diesel engines being used by the Indian railways produce a lot of noise because like in cars due to the high combustion rate the noise levels are very high. This can be experienced in our very own college hostel where the students staying close to the railway track are often exposed to noise levels of more than 90dB causing high levels of irritation and disturbance.
Essay # Psychological Effects of Noise Pollution:
Noise has psychological effects is undoubted. The question is how these effects can be assessed and whether they lead to damage. No clear case has been made thus far for psychological damage caused by moderately high levels of noise, the levels that would cause hearing damage to only a small fraction of the people exposed.
Indeed, fears have been expressed that… over emphasis on damage may backfire when people come to realize that the truth of the matter seems to be simply that people can express violently their dislike about being disturbed by noises. This is recounted vividly by Connell (1972):
A middle-aged woman living in Soho became affected by the incessant noise from a newly opened discotheque. She complained to the management, the Police, the Local Authority but nothing was done to reduce the noise. Her action took the from of suicide.
In Italy a 44 year old man took an overdose of drugs because his eleven children made too much noise while he was watching the Olympic Games on television… In a quiet part of Middlesex with an ambient noise level of 30 to 40 decibels lived Fred, a healthy labourer.
The M4 Motorway was built within a few feet of his cottage home. The resultant traffic caused the noise level to rise to 80 and 90 decibels so this poor man suffered an increase of 100,000 times in the noise level. He took it for some weeks. Discovered there was nothing he could do about it and his action was also directed against the self. He left a note which read “The noise; the Noise; I just couldn’t stand the Noise”…
These are clearly extreme cases of reaction to the intrusion of noise into one’s life. But without question the ubiquitousness of the intrusion, even if less severe or less fatally resented, leads to demands for acoustic privacy which are psychologically no less important than those for visual privacy.
Many people, especially youngster’s think that more sound gives more pleasure, it has been proved that continuous exposure to loud continuous sound could lead to hysteria and permanent hearing damage.
Thus continuous exposure to disco music, trash, heavy metal ar. 3 the variants are very harmful to the ear. It has also been concluded that the old people of the urban areas who are continuously exposed to loud levels of noise are more prone than village folk to suffer from hearing loss.
Thus in our technically dynamic society it is obvious that noise levels can be brought down considerably if the noise control technology that exists today is properly applied. Finally in a more technically sophisticated society, the public would become ever more sensitive to the fine balance between environmental improvements and the cost of the controls that will be required to attain the sought after benefits.
We would discover in the field of environmental improvements that it is not always necessary to plumb the technology to its full depth, with the attendant high costs to society, to attain real and satisfying gains. Finding the point of maximization of environmental protection for the least cost must become a science unto itself.