2. An area for packaging cereals and dried prepared mixes occupies an entire floor of a large building. The area measure

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2 An Area For Packaging Cereals And Dried Prepared Mixes Occupies An Entire Floor Of A Large Building The Area Measure 1 (363.99 KiB) Viewed 41 times

2. An area for packaging cereals and dried prepared mixes occupies an entire floor of a large building. The area measures about 60 m by 40 m by 6m high. All surfaces are poured concrete. The major noise sources are a paper shear, a box former, and a wrapping and sealing machine all located at one end of the room. Some employees are stationed near the machine but most of the employees work on the other side of the room. A weighted sound pressure level in the area away from the machines was measured at about 91 dBA. At the same time the average reverberation time for the room was measured to be about 3 sec. It was desired to reduce the overall levels in the main employee area by about 6 dBA. (a) A consultant suggested the use of hanging baffles to reduce the noise level by increasing the absorption in the room. The baffles under consideration are shown below. The baffles are 0.75m by 1.5m by 0.1 m thick. When they are hung vertically with the spacing shown, the absorption is as = 10 m²-sablne. How many baffles are required to achieve the 6 dB reduction? Is there enough room to hang al 1 of the baffles with the proper spacing? Could you get a 10 dB using these baffles? (b) An intern suggested that the installation of absorptive materials on the room surfaces can also help reduce the sound level. If only ceiling can be used for installation, can this installation help reduce 6dBA? (use any available ceiling materials in the market for consideration) im Employee 40m Work Area [Hoo Machines 凸凸 60m 4. Design a loose-fitting enclosure for the pump motor assembly in problem 2) so that the desired sound pressure level can be achieved. Assume the enclosure to be about 1 m x 2m x 1 m high and completely sealed. Also assume that a diffuse field exists inside the enclosure. For the design, consider only the materials listed in the accompanying tables. Use a linear average of the values at the different frequencies to characterize the material behavior. Your design should be fairly simple to construct and you should try an minimize cost. How would you modify your design to provide for ventilation for the motor?