The noise generated in the environment can never be eliminated completely; however, it can be controlled.
Many new technologies are introduced to curb noise. There are, however, some easy ways to curb noise besides introduction of new technology.
The basic difference of noise pollution from other types of pollution is that it does not leave any residue in the environment, but it creates enormous physical and mental health problem in persons continuously exposed to it for a considerable time.
As we cannot see the sound wave and as it does not leave any residue, it is not given that importance and people are continuously exposed to it.
Thus, it is the demand of the hour to implement new stringent laws, such as motor vehicle act, introduce new regulation to ‘owner speed limits of vehicles, promote education and research creating awareness among the public about the harmful effects of noise pollution through radio, television and newspapers.
The noise created from the heavy machinery used in the industry as well as other community can be curbed by taking measures at the source, at the noise transmission path and at the receivers. Source is the main route of noise generation.
If noise is completely abated at the source the other two need less nourishment. However, due to various machinery parts involved in the source, noise cannot be abated completely. So if we take care of the three areas all together, noise can be eliminated to a maximum level.
(a) Control at Source:
In the industrial establishment, it can be done by proper design, proper operation and regular maintenance of the machines. The industry should be located at open spaces far off from the residential areas.
As far as community noise is concerned, the loud speakers, radio and music system should not be allowed to cross the threshold intensity.
(b) Control at Path:
The noise transmission path can be covered with such material, which can absorb the sound, can insulate the sound. Sound absorbers can be glass wool, porous panels, perforated panels, tiles, carpets, curtains, etc. These materials are generally porous which reduce reflection of sound.
Sound insulators reduce sound transmission through barriers. Sound insulating materials could be glass, steel, ceramic materials, concrete, etc.
Vibration control of the machinery is generally done by mounting the machine on a base plate or an inertia block like concrete block. The various other measures of path control resources are:
(i) Acoustic enclosures:
This can be done by putting close fitting enclosure around the machine, keeping high noise generating machine in a separate room at a relatively long distance. The walls of the enclosures are also made with acoustically lined materials, such as glass fiber or fiber wool inside the wall.
(ii) Noise barriers:
This can be done by constructing walls with hard and dense materials to reflect sound or porous material to absorb sound and by placing them closest to the noise source.
To achieve high degree of efficiency, the gaps or the joints of barriers are eliminated, so that the sound does not leak through and reduce efficiency. However, sound will lead the machine operator to get exposed to the noise. Some common examples of noise barriers are glass fibers, brickwork, fiberboard, etc.
Silencer is a hollow material, shaped in such dimensions that it reduces sound transmission, but allows the gases (incoming as well as outgoing) to pass through it. The silencer may absorb the sound or reflect the sound or if designed properly can function in both ways in a single system, thereby reducing noise intensity.
The materials generally used are stainless steel, tin plate, stainless iron which acts as a reflector of sound and when coated with fiberglass the sound intensity reduces to a large extent due to the absorption of sound.
Silencers are generally used in automobiles and transport vehicles, Reduction of noise produced due to vibration of machine: Installation of a machine on the floor contributes to high noise pollution to a large area around it. The best way to solve such problem is to place the machine on a thick steel plate, isolated from the other by a thick block of rubber.
No matter how much precaution be taken, how much technology is introduced, it is not possible to nullify noise. Thus, personal protection is very essential for the safety of the workers. For such cases, ear protection and in extreme cases personal isolation will help a lot. The commonly used hearing protectors are earplugs, ear muffs, etc.
In an extreme case, the person can be isolated from the source to stay in an air conditioner enclosure or a thick walled sound absorbing room, with a viewing window and occasionally, can go to the operating room thus, minimizing noise exposure. In an industrial establishment, administrative control helps a great deal. The workers should be given shift duties, so that an individual or groups are not exposed to the noise for a longer period of time.
Lastly, it should be mentioned that plants and trees have a greater capacity for reduction of noise. Plants are efficient absorbers of noise, especially noise of high frequency. Thus, plantations along highways, streets and industrial areas should be done.
This is one of the reasons due to which rail traffic noise or other road transport noise is less when they run through highways having green plantation on both sides. Air traffic noise can be curtailed by growing green vegetation belt of short to medium height around the airport.