Chapter-17
Noise Pollution
Noise Pollution:
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. In the following paper, the cause and effects of noise pollution
All sounds are not noise. Noise is any sound that is unwanted and goes beyond its certain limit, i.e., above 80 decibels Harsh sounds of lightening and thunder, noise produced by machines, automobiles, railways, aero planes and the blaring sound of loudspeakers and some musical instruments come under the category of noise pollution.
More and more noise is the creation of modern civilization and has now become a major environmental pollutant, specially in urban areas. The most notable effect of noise pollution is on hearing. It may cause total loss of hearing that may result in the reduction of worker’s efficiency.
At the higher levels, it may lead to physical and psychological damage. There is evidence that noise is one of the major causes of stress and anxiety. It also causes headaches and irritability. It may also affect blood pressure and heart beat. Air, water and noise pollutions are very common which are creating havoc for all types of life. They have disastrous transnational consequences.
There are two types of hearing loss: conductive and sensorineural (see fig.1 for anatomy of the ear). 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 (Bugliarello, et al., 1976).
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 (Bugliarello, et al., 1976).
Mitigation of potentially harmful amplification occurs via muscles of the middle ear. These muscles act as safety device protection 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 bout 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 fibers and transmitted to the brain. It is the decoding of all the information that enables a person to distinguish the unique ant separate sounds of a violin, trumpet, and clarinet, even all three are playing the same note.
The Occupational Safety and Health Agency (OSHA) has set the danger level at 95 decibels (dB) and above for 4 or more hours per day as likely to induce permanent hearing impairment
The organ of corti, a gelatinous mass, is on of the best protected parts of the body, encased as it is within the cochlea which in turn is deeply embedded in the temporal bone, perhaps the hardest of the 206 bones (Bugliarello, et al., 1976). None the less, loud noise can damage the hair cells and the auditory nerve, producing at times, depending on the type of noise, sudden and often total deafness.
Sustained noise over a period of time can also engender sensorineural deafness in the form of gradual losses in hearing. This is the most common loss in teenagers today listening to loud rock music (Bugliarello, et al., 1976).
Until a few years ago, sensorineural deafness could not be helped by hearing aids. However, with advances in electronic wizardry and miniaturization, devices for insertion into the auditory canal are available.
Cause and Effects of Noise Pollution
Daniel G. NunezInterdisciplinary Minor in Global Sustainability, University of California, IrvineStudent papers, Spring 1998Instructor: Peter A. Bowler
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