Sound-Absorbing Materials 6. Enclosures to Reduce Noise 5. When a source of noise is enclosed in a room, the direct sound will decrease as the distance from the source increases (as is the case in open air). To be effective, however, the coating should be at least equal in weight to the panel. (ii) Reducing the Potential Noise Energy: It is well known that the amount of noise radiated from a surface depends on the amplitude of the vibration and on the area of the radiating surface. The greatest number of people are protected from the noise by this means, and moreover, the noise control treatment is less expensive. Occupational noise is the amount of acoustic energy received by an employee's auditory system when they are working in the industry. The cover should, moreover, be coated with a layer of damping compound of equal weight to reduce the effects of resonance. In some cases, a different size may be required for each ear. Ear Protection. A temporary increase in damping, to reduce the noise from the riveting of steel plates for example, can be obtained with sand bags, or even by ensuring that the plate is continuously supported over its whole area. All noise exposure is limited to 87 decibels. To reduce noise pollution, industries have to be kept away from the populated area, rules and regulations on usage of horns and loudspeakers need to be frame, maintaining large machines from time to time so that they do not produce loud noise. Often a rattle can be eliminated merely by securing a loose panel. Note: these regulations do not apply to members of the public in a non-work environment. Sound-Absorbing Materials 6. In many cases, a large area of material has been used with negligible effect because the mounting has been too stiff. Sound-absorbing material should be used inside an enclosure designed to reduce noise. Textile and pollution: The textile process deals with production of fiber, yarn and fabric followed by pre and post chemical, mechanical process. If the noise emission from an impulsive source is not too frequent, an appreciable reduction in the average noise level can be obtained by sound-absorbing treatment. Even in factories where the noise has been reduced to acceptable levels for the majority of workers, some operators of noisy machines may still be exposed to noise levels that are much higher. Ways to achieve this include: Modifying the paths which noise travels to those exposed can be one of the most effective ways to reduce noise pollution in the workplace. Finding effective ways to prevent and reduce pollution (in air, water, or land) can seem difficult and downright overwhelming. A similar arrangement is necessary if a machine needs to be bolted down to achieve sufficient rigidity. An enclosed machine may be noisier in fact (unless proper precautions are taken to isolate its housing) than if it were not enclosed. For any one constant noise source, the reflect sound level will always be lower in a large enclosure than in a small one. A small partial enclosure around a single machine is one of the few forms of noise control that protects the operator from the noise of his own machine. By controlling noise we can control negative health effects that noise pollution has on everyone. This reduction in the intensity of sound will continue up to the boundaries of the enclosure. The amplitude of vibration is then limited only by the damping in the material. The advantages of this method may make its extra cost justifiable in special cases. This, however, would only be so if the cavity between the walls were impracticably wide, and there were no indirect transmission through floor or ceiling. When a factory is planned, the planners should keep in mind that many of the very noisy processes have alternatives that produce far less noise. In addition to resilient materials, pneumatic suspension has also been suggested as a method of vibration isolation, although it would be more expensive than other forms of suspension. It is a legal requirement to protect the wellbeing of your workers hearing – so work to reduce it as much as possible. wide, the noise reduction obtained at low frequencies is no better (and may even be worse) than for a solid wall of the same total weight. To increase the effectiveness of the double-leaf enclosure at low frequencies, the cavity must be made 15 to 30 cm wide. The directional properties of a source are also determined by the size of the radiating surfaces. Noise pollution is commonly generated inside many industrial facilities and some other workplaces, but it also comes from road, rail, and air traffic and from construction activities. In some particularly noisy industries, the methods of noise reduction described in the preceding sections may not be adequate to reduce the noise to safe levels. For a given weight of material, a higher sound reduction can sometimes be obtained by using a double-leaf enclosure. Subsequently, there should be proper supervision to ensure that the ear protectors are worn regularly. A direct air leak (through a hole or through porous material) will transmit the air pressure fluctuations, propagating the noise without reduction. Noise Pollution. Noise caused by turbulence at outlets, valves, and bends in pipes and ducts can be reduced by careful streamlining as well as by lowering the velocity of air or gas passing through them. Way # 1. However, the noise from service equipment can often be as intense as that from the production machinery. Some workers find them uncomfortable at first, but soon become used to them, and can wear them for long periods. A permanent increase in damping (in resonating parts of equipment, for example) will be achieved if the surface concerned is coated with a chemical compound of the kind used for under-sealing cars. In fact, the issue of industrial pollution has taken on grave importance for agencies trying to fight against environmental degradation. The fastenings also should be isolated, or they will “short-circuit” the gasket. Where the panel concerned is a permanent part of the equipment, it can be stiffened by corrugations or by adding ribs. blowing dust from surface, reducing excess air can reduce air pollution from industries Among these two factors, the amplitude is determined by the resistance of the surface to oscillatory motion, and the power available to drive it. For example, the reduction in vibration transmitted to the floor will enable the live-load allowance for vibration to be reduced, and the reduction of shock loading within the machine may increase its useful life. Noise can hardly be a major consideration in the choice of an industrial process; but it must be taken into account as one of the economic factors. One of the basic principles of noise control is that noise should be reduced as near the source as possible. (e) Reducing the noise produced from a vibrating machine by vibration damping i.e. However, what you can do is update you can make modifications that’ll help you control the noise level on construction site. In factories, the vibration isolation of service equipment is often neglected. There may, for example, be a direct air path over the top of a partition (as through a porous sound-absorbing ceiling). Where flexible connections are impracticable, the introduction of bends into a pipe will reduce its efficiency as a conductor of vibration. With densely packed machinery in a factory, the reduction in a factory, the reduction in sound level due to the absorption is very small. Industrial Noise Pollution This is posing to be a big challenge with very passing day and is a threat to safety and health of the people who are working in … The noise radiated by machinery guards can be minimized by making them of perforated sheet or of wire mesh. The regulations include the stipulation that workers in an environment that exposes them to 85 decibels (daily) must be given sufficient hearing protection. Carry out a noise impact assessment if you are unsure where your noise issues are most persistent or how to deal with them. Have industrial pollution control policies in place, especially if you operate a factory or production plant. Their shielding effect is mainly limited to the more directional high frequencies. Some of the proprietary mounts have built-in leveling devices, and since vibration mounting stops the machine from “walking”, holding down bolts are not required. In an overall treatment, the walls should not be covered at the expense of ceiling unless the space is high and narrow, though local absorption on the walls will reduce the noise from nearby machines. The vibration can be transmitted, in this way, for long distances with very little reduction. 4. Since the average noise near the source is also lower, there is some relief for the machine operator in the treated factory, though the reduction in the peak noise levels is negligible. The ways are: 1. A specific degree of thermal insulation for the roof structure is required for certain factory buildings, and the material used for this purpose may also reduce the noise in the building at no extra cost, provided it is correctly installed. Wherever it is possible, the opening should face a wall covered with sound-absorbing material, or should be baffled with a screen of the same construction as the enclosure. Most machine tools are not likely to generate low-frequency vibration, and the resilient mount may then be placed between the machine casting and the floor. This is particularly needed if the doors form a large part of the total wall area. Vibration from rotating machinery can usually be reduced by dynamic balancing. Buildings and high walls between the noise source and the listeners will act as screens. If the absorption coefficient of the ceiling or floor is close to unity, the reduction of sound level with distance will be almost equal to that in open air. The total area of such a mat is important; and so is its thickness. Frequently, the designer of factory building faces the problem of deciding what part of a factory is likely to be noisy. In this case, the decay of the noise level (once the source has stopped) is directly proportional to the amount of sound absorption in the space concerned. One should also keep in mind that excessive noise from a tool, for its type, size and power level, generally indicates low mechanical efficiency. 3. For reducing the noise in a factory, equally important is the isolation of a vibrating source within a machine from other parts that can radiate the noise. To obtain an appreciable amount of noise reduction, the duct should incorporate several right- angle bends; otherwise, it needs to be very long. With fairly complete enclosure (such as that provided by a tunnel), a reduction of about 20 dB above 500 Hz may be achieved. In existing factories, there may be no clear surface that can be lined with sound absorbing material; or its installation may greatly interfere with production. Noise may, for example, be radiated by the sheet metal enclosing the moving parts. This includes using noise-absorbent materials in the walls (foam), or keep the workflow of your factory efficient enough to keep workers and machinery as far apart as possible. The total intensity of sound at any point, therefore, will consist of a direct component and a reflected (or reverberant) component. In light of these regulations, reducing noise pollution in the workplace is vital for both your workers and your business. Other noises caused by friction in machines, conveyors, and roller trolleys can be minimised by proper lubrication. Here is why control of noise pollution in the workplace is important and how you can work to reduce it. Any form of pollution that can trace its immediate source to industrial practices is known as industrial pollution. In the case of small pneumatic tools, for example, this can be achieved by incorporating in the tools an exhaust collecting sleeve. Waxes cotton wool, on the other hand, will give more reduction; but it still does not compare with a well- designed earplug. (b) By reducing the efficiency of the surface as a radiator of noise. Noise Reduction at Source 2. For example, porous materials absorb high-frequency sound more efficiently; but their low-frequency absorption can be improved by increasing the thickness of the material, or by mounting them over an airspace. The process used for production determines, to a very large extent, the noise problem in a factory. Consequently, sound absorption treatment does not attain its maximum effectiveness until machine spacing’s of more than 10 m are used. Musical instruments sound should be controlled to desirable limits. 2 as a function of average machine spacing. If a high degree of noise reduction is required, double doors with a large airspace between them will be necessary. Such a ratio will reduce the vibration transmitted by 87% (equivalent to a noise reduction of about 18 dB).The discussion given above applied to steady-state vibration (for example, the vibration from an electric motor); but the vibration can also be impulsive (for example, the vibration from a punch press). Partial Enclosures and Screens 7. Any parts of the enclosure construction that, although airtight, transmit sound more easily than the rest will have much the same effect. But as the distance between the source and the listener increases, the total sound level decreases to a point where the reflected component alone determines the noise level. The reason is that the acoustic energy is spread over a larger volume in the case of a large enclosure. This requires a reasonably stiff mount. If the dimensions of the radiating surface are much greater than the wavelength of the sound generated, the sound will be emitted primarily in one direction. The build-up of reverberant sound within an enclosure can be controlled by the use of sound absorbing materials. Often the noise excites a high-frequency resonance. The resilient material used for vibration isolation may be in the form of a pad, or of a proprietary mounting. 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