Everybody in present time talk about noise pollution, but no one is trying to reduce it. When someone get hurt from noise pollution then that person got learn a lesson for reducing noise pollution. We use to listen music at high loud volume why? Because we want our entertainment but we never thinks about that high volume which is affecting another person who don't want to listen. Why we are making others to listen our loud. we should listen upto that limit which is sufficient for us. Everywhere noise is increasing. People are using horns at red lights without any use. No body has work on a road on red light. So people should learn not to use horn without use. We should all reduce this noise pollution.
The word noise is derived from the Latin term nausea. Noise has been defined as a sound without agreeable quality or as unwanted or undesirable sound. This is a subjective definition as some desirable sound for somebody (fast music) may be noise for some other person. So defining it in a better way we can say that noise is wrong sound in the wrong place at the wrong time. A given sound is pleasant when soft but noisy when loud. It may be acceptable for a short time but unacceptable when prolonged. It may be intriguing when rhythmic but noise when randomly repeated. Noise is defined in law as, excessive, offensive, persistent or startling sound.
Like air and water pollution noise is also emerging fast as a major pollutant to the environment. The roar of jet planes, honking of buses, the screeching of rushing vehicles, wailing of emergency vehicle sirens, whistling of railway engines, back fire from motor vehicles, the din of factories, the thunder of construction machinery, are contributing to the high level of noise. The noise is just not confined to the urban area but the countryside is also being shaken by the rattle of motorized farm implements, pump sets, tractors, and buzzing of motor vehicles etc. Along with these the increasing use of televisions, sound systems and loudspeakers without any check on their volume is also contributing to the growing noise levels.
Noise problem can be divided in two categories. First is the community noise wherein one is concerned with annoyance caused to people in their indoor environment. It is the intrusion of noise inside the dwellings above the allowable level mainly from vehicular traffic. The other is the intense sound that exists in some workplaces like factories and traffic islands where there is a real danger of permanent physical damage.
Prolonged exposure to excessive noise produces adverse physiological effects such as hypertension, annoyance, disturbance in sleep and deafness etc.
The noise has so far not been regarded as a fatal pollutant because so far it was within limits. Except in industrial areas and big cities noise pollution was not prominent and hence generally remained ignored from being treated as an environment pollutant. With the increasing industrialization and commercialization of society and with consequential increase in noise producing automobiles and machines, noise has become a slow poison to mankind. It is a matter of thought that whether we should accept the increased noise as a price for progress, or should shun the new technological advance all together to lead scheduled life. The other better way is to devise and implement noise controlling techniques to reduce the adverse impacts of noise.
LEVELS OF NOISE
The sound pressure of the faintest sound that can be heard by a normal healthy individual is about 20 micro-Pascal. The loudest sound produced by a Saturn rocket at the lift off stage is about 200 Pa. This large variation in sound pressure (varying from 20 µ Pa to 200 Pa) is usually avoided by expressing sound pressure on a scale based on the log of the ratio of the measured sound pressure and a reference standard pressure. Measurement on this scale is called levels. The sound level (L) is thus represented as,
L = log10 Q/Q0 (Bels)
Where Q = Measured quantity of sound pressure or sound power or sound intensity.
Q 0 = Reference standard quantity of sound pressure. L = Sound level in Bels.
A Bel is a large unit so for convenience it is divided into 10 subunits called decibels (dB). So when sound level is expressed in decibels.
L = 10 log10 Q/Q0 (dB).
According to World Health Organization (WHO) a level of 45 dB is considered a safe noise level in a city. However, a noise level of 65 dB can be tolerable as per the international standards. A report from National Physical Laboratory (India) shows that there is an increase in the background noise level at the rate of 1 dB per year.
THE NATURE OF SOUND
Sound is the sensation caused by a vibrating medium acting on the ear, but the term is usually applied to the vibration itself. The source of sound is most often some vibrating solid body like a string or a sheet which generates vibrations in the air, but it may be generated by vibrations of a gaseous medium, as such the air in a whistle or flute. The medium conveying it to the ear can be a gas (air) or a liquid. In which the vibrations are transmitted as a longitudinal wave motion, i.e. successive compressions and rarefactions of the molecules.