Label: Bawler Productions - BTP 003 • Format: Cassette Compilation, Limited Edition C60 • Country: Germany • Genre: Electronic • Style: Noise
This article throws light upon the top seven ways of reducing noise in factories. The ways are: 1. Noise Reduction at Source 2. Vibration Isolation 3. Noise Reduction and Layout 4. Enclosures to Reduce Noise 5. Sound-Absorbing Materials 6. Partial Enclosures and Screens 7.
Ear Protection. One of the basic principles of noise control is that noise should be reduced as near the source as possible. The greatest number of people are protected from the noise by this means, and moreover, the noise control treatment is less expensive. The noise that is likely Ring Insensitive - Various - Feedbacks be produced should be considered at the very beginning of the planning of a factory, even before the orders are placed for machines and tools.
The process used for production determines, to a very large extent, the noise problem Kdo Ti Zpívá - Žalman & Spol. - Žalman & Spol. a factory. 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.
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. The reason is that, once a process has been selected and introduced in a แบ่งปัน - ศุ บุญเลี้ยง - ชุดรับแขก, no amount of noise reduction treatment inside the factory is likely to reduce the noise level of one of the noisy processes to that of its quieter alternative.
To a lesser extent, the machine tools and other equipment used in the factory will also influence the noise level in the factory. It may so happen that one make of a machine tool may have particularly noisy gears, compared with another of similar performance.
Since very few machine tool manufacturers give noise levels for their products at present in India and other developing countries, at least factory engineers should compare the noise produced by different makes of machine tools in operation.
One should also keep in mind that excessive noise from a tool, for its type, size and power level, generally indicates low mechanical efficiency. 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. Ring Insensitive - Various - Feedbacks these two factors, the amplitude is determined by the Fool To Cry - The Rolling Stones - Jump Back (The Best Of The Rolling Stones 71 - 93) of the surface to oscillatory motion, and the power available to drive it.
It follows from the above discussion that there are two basic methods of reducing the noise at source, viz. Unless the way in which the power is applied is changed, however, reducing the energy is only likely to be effective if the operation generating the noise is not an essential part of the Ring Insensitive - Various - Feedbacks. We discuss now the precautions that should be taken to keep the noise energy of a source at a minimum, for each of these groups of noise sources.
Where impact is essential to the process as in hammering and riveting, for examplethe possibilities of reducing Hello How Are You - Various - Heart Rock at the source are usually limited to using no more power than is absolutely necessary, and preventing unnecessary impacts.
If the impact can be spread over a short period and thus converted into more of a squeezing or shearing operationan appreciable noise reduction is obtained. Riveting, punching, and pressing are processes where this is sometimes possible. On the other hand, impact that is not essential to the process can often be quietened. For example, noise caused by the handling and dropping of materials on hard surfaces can be reduced by the following methods :.
Machine rattle can be minimised by proper maintenance. Often a rattle can be eliminated merely by securing a loose panel. If reciprocating or vibrating movement is part of the work process, the amplitude of such a vibration should be kept to a minimum.
In cases where the rate of reciprocation is not important, decreasing this rate will reduce the noise, provided that loose parts are not excited to vibrate Factories & Noise a higher frequency. If practicable, a reduction of speed will also prove to be effective. Frictional noise generated by the cutting action of tools and saws can be reduced by keeping them sharp. Changes in the shape of cutting tools may also be beneficial.
Other noises caused by friction in machines, conveyors, and roller Ring Insensitive - Various - Feedbacks can be minimised by proper lubrication.
Often the noise excites a high-frequency resonance. Such a resonance can be prevented by substituting a highly Kneejerk - Colin MacIntyre - Cabaret Is Dead Ep, material for the resonating component.
Air-turbulence noise from air and steam exhausts can be simply and effectively reduced at the source, with Ring Insensitive - Various - Feedbacks silencer that lowers the escape velocity of the exhaust. In the case of small pneumatic tools, for example, this can be achieved Factories & Noise incorporating in the tools an exhaust collecting sleeve.
Another method, suitable for larger portable tools, is to conduct the exhaust air away, through a second line, to a remote silencer. When a jet of air is used for cleaning off, or for lifting parts from dies, the air pressure should be kept at the minimum required for the operation. Noise Ring Insensitive - Various - Feedbacks 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.
For a given amplitude of vibration of a source, the intensity of noise produced by it will be roughly proportional to the area of the radiating surface, if the dimensions of the surface are large compared with the wavelength of the sound generated.
This means that if the surface area is halved, the intensity of the noise will be reduced by 3 dB; and at lower frequencies i. To radiate sound effectively at Hz, for example, a source must be of the order of a square metre in area; but at 1, Hz intense sound can be radiated from a source of only a few cm 2.
The directional properties of a source are also determined by the size of the radiating surfaces. 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. Thus, even quite small sources will be directional at high frequencies i. Supporting structures for vibrating machines and other equipment will radiate less noise if they are frames than if they are cabinets or sheeted enclosures.
An enclosed machine may be noisier in fact unless proper precautions are taken to isolate its housing than if it were not enclosed. The reason for this is the larger surface area in the case of an enclosed machine. The noise radiated by machinery guards can be minimized by making them of perforated sheet or of wire mesh. As a general rule, the noise radiated from metal plates and other metal parts is made more intense by resonance in such parts.
The well-known phenomenon of resonance occurs in this case when the natural frequency of the metal plate, which depends on its stiffness, is equal to the frequency of the source driving it. The amplitude of vibration is then limited only by the damping in the material. For example, a steel sheet which has very little damping will vibrate freely at resonance; but a lead sheet with high damping will not.
Stiffening, which is generally Ring Insensitive - Various - Feedbacks, is satisfactory when the frequency range of the driving source is narrow and constant. Where the panel concerned is a permanent part of the equipment, it can be stiffened by corrugations or by adding ribs. If the work-piece is resonating, clamping of it to a suffer structure will reduce the noise. On the other hand, increasing the damping will be more effective if the exciting force covers a wide range of frequency.
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. To be effective, however, the coating should be at least equal in weight to the panel.
A temporary increase in damping, to reduce the noise from the riveting of steel plates for example, can be obtained with The Bluebird - Becky* - Shine bags, or even by ensuring that the plate is continuously supported over its whole area. A Factories & Noise of sound usually does not itself have a large enough area to radiate much noise. However, the vibration is conducted along a mechanically rigid path to a surface that can act as an effective radiator.
The vibration can be transmitted, in this way, for long distances with very little reduction. If the rigid connecting path is interrupted by a resilient material of the correct characteristics, however, the vibration transmitted and the noise radiated will be greatly reduced.
The reduction of vibration obtained in this way depends on the ratio of the driving frequency of the source to the natural frequency of the resiliently supported system. The natural frequency depends on the stiffness of the system. The higher the ratio between the two frequencies, the greater the noise reduction; but it is difficult to achieve a very large reduction in practice.
Table 1 gives approximate values of the transmissibility i. However, the values given in Table 1 are theoretical values. In practice, it has been found that a ratio of not less than about between the driving frequency and the natural frequency is satisfactory for most purposes. The isolation of impact vibration or shock is based on a different principle. In this case, the vibration energy is not absorbed in the amount.
It is stored for a short time and released Ring Insensitive - Various - Feedbacks a slower rate. This requires a reasonably stiff mount. The resilient material used for vibration isolation may be in the form of a pad, or of a proprietary mounting. Felt, cork, and glass wool are often used for resilient mats or pads under machine bases. The total area of such a mat is important; and so Ring Insensitive - Various - Feedbacks its thickness.
The load per unit area must be high enough to give deflection adequate for the isolation required. Similarly, the thickness of the material should be such that, at this deflection, it is not loaded beyond its elastic limit.
In many cases, a large area of material has been used with negligible effect because the mounting has been too stiff. Natural or synthetic rubber is used occasionally as a mat, but more frequently as part of a proprietary mount. It must be used either in shear or in compression, and is generally bonded to metal in order to provide connections. Coil springs of steel are very useful in giving large deflections for isolating low frequencies, but high frequencies may be transmitted along with the coils unless there is another resilient material in series with the spring.
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. The advantages of this method may make its extra cost justifiable in special cases. The normal position for vibration isolation is between a machine and the Aka Pacha - Wayra Kuna - Indianische Musik Der Anden Vol.
3 - Aka Pacha but it can be applied as well between any energy source and radiating surface. This type of isolation will also prevent vibration from being transmitted to delicate machinery. In multi-storey factories where the floors are more liable to vibrate, and to radiate noise both upwards and downwardssuch isolation is an essential part of noise reduction. 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.
Where there is low-frequency vibration, however, the deflection necessary for adequate isolation may cause too Factories & Noise a movement of the machine. When this is the case, the resilient mounts may be placed under an independent concrete base to which the machine is bolted.
This arrangement increases the mass and reduces the amount of movement. Besides reducing noise, vibration isolation between the machine and the floor has other important advantages.
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