Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Audiology and hearing health professionals in developed and developing countries wikipedia , lookup
Auditory system wikipedia , lookup
Sound localization wikipedia , lookup
Sensorineural hearing loss wikipedia , lookup
Olivocochlear system wikipedia , lookup
Noise-induced hearing loss wikipedia , lookup
Abdul Barey Shah Noise Pollution Sound is the main means of communication in many animals including humans. A low sound is pleasant and harmless. A loud unpleasant sound or an unwanted sound of any kind is called noise. The world noise is derived from the Latin ‘nausea’ meaning a feeling of sickness at the stomach with an urge to vomit. Noise is defined as unwanted sound”, “Sound without value” or “disagreeable sound” or wrong sound, in the wrong place at the wrong time.” Noise pollution is unwanted sound “decomposed into the environment without regard to the adverse effect it may have (Odum). Noise pollution may also be defined in a number of ways e.g. Any unwanted electromagnetic signal that produces a jarring or displeasing effect and which interferes with human communication comfort and health. A persistent, often excessive and disturbing level of noise considered as a harmful factor in a given environment, is called noise pollution. The sound intensity is measured in decibel (dB), which is tenth part of the longest until Bel, named after Alexander Graham Bell. One dB is equal to the faintest sound a human ear can hear. Sound beyond 80 dB harms hearing system and so it can be safely regarded as pollutant. The largest noise a man can hear without much discomfort is thus about 80 dB . The central pollution control Board committee has recommended permissible noise levels for different locations as given in table 4.5: Table 4.5 Noise standards recommended by C.P.C.B Committee: Sources of Noise Pollution The source of noise are varied and too many. Noise is either natural such as thunder or manmade. The sources of manmade noise are more in urban and industrial areas than in rural areas. The sources, in general may be stationary or mobile. For a better understanding of the subject, the sources of noise can be classified in following categories: (i) Transportation / Traffic Noise: It includes road traffic noise, aircraft noise and rail traffic noise. With the increasing number of motor vehicles and trains inhabitants of cities are generally subjected to a high level of transport noise which gradually deafens them, as compared to those living in quieter towns. For example the din at the railway station in Bombay often rises above 75dB and is considered comfortable for the human ear. But the hooting of trains creates strain on ear because the noise level rises to 130dB, decreasing to 90dB at a distance of about 10 meters. Aircraft noise is variable and intermittent, and is not continuous like the road traffic noise. This source has been increasing during recent years especially close to international airports, and has now become a serious problem. Cities around the world have banned or reduced flights at night, and also prescribed noise limits. Noise generated from highway traffic is one of the major sources of noise pollution. Highway noises are of two types, viz, noises generated by individual vehicles and noises generated by a continuous flow of vehicles of all types. (i) (ii) Industrial Noise: In Industries, noise is the byproduct of energy conversion. The major sources of noise in an industrial plant may include electromechanical machines (like motors, generators etc) impact machines (like punching, stamping hammers, etc) combustion processes (furnaces), fluid motion (compressors, fans etc) and other mechanical parts (like shafts, gears etc). This is also called occupational noise and workers in these industries are subjected to noise for about 8hours daily. Neighborhood Noise: It has been defined as the variety of sources of noise which may cause disturbance and annoyance to the general public. This type of noise includes disturbances from household gadgets and community. Common noise makers are musical instruments, TV, VCR, radio, transistors, telephones, washing machines,vacuum cleaners, fans, mixers, coolers, air conditioners and loud speakers etc. It includes the noise generated during functions, festivals, religions activities (Like Marriage ceremony, Diwali, and Holy etc). Thus the variety of sources of noise may cause disturbance and annoyance to the public. Effects of Noise Pollution: Noise affects human body in an number of ways, these may be classified as auditory -effects and non- auditory effects. (i) Auditory effects: Noise can damage the ear and cause temporary or permanent noise induced hearing loss (NIHL) depending upon the intensity and duration of the sound level. This is seen in those persons who are exposed to high noise levels over a long span for example workers working in textile industries steel industries are exposed to more than 105 dB for eight hours per day and suffer from temporary or permanent noise induced hearing loss. If the ear receives a noise level of over 90 dB for more than few minutes then the auditory sensitivity is reduced. This effect is called the temporary threshold shift (TTS). The most commonly occurring ear damage is caused by continuous periods of high intensity noise as found in some factories and other work situations. Under these conditions the permanentthreshold shift (PTS) and progressive hearing deterioration results. Besides progressive hearing loss, there may be instantaneous damage or acoustic trauma which may be caused by very high intensity impulse type noise resulting from an explosion or sudden excessive noise of over 150 dB. (i) a. b. c. d. e. Non- Auditory effects: These are also alarming because of the fact that they may also cause severe diseases. These effects include. Speech Interference: A person faces problems in understanding another person talking to him in an environment with high background noise level. Noise levels thus affect the efficiency of schools, offices and other working places where communication is of vital importance. External sounds can also interfere with conversation and use of the telephone as well as the enjoyment of radio and TV. Sleep interference: Noise causes interferences in sleep and it is a health hazard, since it deprives a person of the restorative process for his organs to renew their supply of energy and nutritive elements provided by a good night’s sleep. The loss of sleep from noise affects personal well being and job performance. The preferable level is below 40 dB. Task interference: The effect of noise on the human performance of tasks is a complicated subject that is under continued study. Many people complain that noise makes them mentally ill and reduces their working efficiency. Noise actually reduces the accuracy of work than to reduce the quantity of work. Effects on Health and Behavior: One of the non- pathological or psychological effect of noise is physical or mental fatigue and lack of concentration. In industrial stations this effect results in lowered efficiency, reduced work rate and higher chances for accidents. Noise also causes anxiety and stress reactions and in some cases fright. Pathological and other effects: These effects are produced by particular noise frequencies causing vibration or resonance in human bodies. High frequency sound above, the normal audible range can affect the semi-circular canals of the inner and make one suffer from nausea excessive fatigue headaches and vomiting. It has been observed that there are increased incidences of birth defects, stillbirths, and unusually low weight among children born to mother living near high noise producing sources such as air ports, blast sites etc. Control of Noise Pollution According to a WHO report “of all environmental problems noise is the easiest to control”. The efforts to control noise are usually aimed at lowering the sound intensity of the noise source. The main methods to control noise are: (i) (ii) (iii) (iv) (v) (vi) Noise producing industries, railway stations, aerodromes should be located away from human settlements. This acoustic or proper zoning should be strictly enforced. Railways and main roads should be away from dwelling and working sites. Noisy machines should be installed in sound- proof chambers. Proper lubrication and maintenance of machines can reduce noise, quieter machines should be produced to replace the noisy ones. Protection to workers can be provided through wearing devices such as ear plugs and muffs or cotton plugs which reduce the noise and protect the receiver. Attempts can also be made to deflect the sound away from the receives e.g. mechanically directing jet exhaust noise upward instead of directing it downwards. This will reduce a jet plane sound to a great extent. (vii) Noise can be reduced by prescribing noise limits for vehicular traffic. Formation of silent zones especially near hospitals, nursing homes, schools would be an effective measure. (viii) Planting of trees in many rows on both sides of roads and around residential areas as well as industrial areas or industries. (ix) Suitable legislative measures should also be taken to project the public from noise pollution and to punish offenders. (x) People should be educated through mass- media like TV, radio, news reels in Cinema halls about the harmful effects of noise pollution will help in long way in controlling noise pollution.