Hewitt (2005) commented on the exhaust silencer industry as being describe as a ,grey art,where only those who work in the industry understood something of the product design.Customers have traditionally accepted the silencer manufacturer word that product would be correct with noise level required. Very few installation were actually measured and acceptance was by the ear methods.The silencer industry continued to manufacture ancient designs,due to lack of qualified design engineers and more importantly,,non - availability of facilities to test new designs and prove performance. Over the years price became the issue rather than performance and in recent years several installation have failed noise test and proved very costly to add attenuation and bring them up to specification.The traditionally types of exhaust silencer are reactive and absorptive. The reactive design is most effective at low very frequencies and comprises perforated or plain tube contained in empty chambers. The absorptive design on the other hand,suppress noise by absorbing the sound wave within a mineral fiber infill.The combination silencer as the name implies, combine both principle within a common body. As previously stated that the technology is archaic,because it was based on designs from the innovators of between 70 to 80 years ago (Hewith, 2005).
Meanwhile, a company in France designed and developed its range of exhaust silencer using ground braking computer modeled technology developed in their own software house.
Stopson (2005), allowed her engineers to think beyond the previous accepted silencer designs and actually test it on engines. They found that to attenuate the problem of exhaust noise, you must firstly develop that which suppresses the dominant frequency to protrusive tonnes .The new thinking has been particularly effective in the relative chamber of silencer, low frequency needs volume to suppresses the sound waves. but the problem is that less and less space is being provided for exhaust silencers therefore the priority for the design was to inverse low frequency performance without increasing size .The design lay in developing a unique twin volume chamber that work more effectively than traditional perforated tube designs after a rigorous testing procedure,the performance was known and a silencer was applied with absolute confidence that the specification could be met.This known performance often reduces the need for a secondary silencer,because the necessary attenuation could be achieved with a single unit.This one for two solution not only reduces the cost ,but also save space for the user for the future the priority is to keep pushing the boundaries to develop reactive chambers, that produces more attenuation at the vital 63 - 125 HZ frequency . As environmental noise level are driven lower and lower only those companies that invested in the engineers ,by providing facility for effective design will be able to meet, more stringent market requirement .It is unlikely that the demand for energy will diminish,while the demand for noise attenuation will increase , So it is assured that those companies invested on development of effective products are the one that will succeed .A palace,s electricity generating engine comprise four diesel powered engine typed Deutz Bu 16 m 628 - each generating approximately 200KVA .Acoustic confirmed pressure level from the engine exhaust to be 108dBA a totally unacceptable noise level for daily living was un -attenuated to LP - 45dBA at 10 meters .These was achieved through the utilization of primary silencer.The primary silencer used were based on the reactive principal in order to reduce the low frequency in sound emissions, while the secondary silencer were built on the absorptive principle to reduce minimum and high frequencies. All the equipment used were made of stainless steel.The primary were placed inside the plant room while the secondary silencer were positioned outside the plant room on the roof of the building.(Malcom,2005) .
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