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Unformatted text preview: the walls and ceiling are ½ in Gypsum nailed to 2x4 studs. a. Calculate the room constant R To reduce sound the sound levels the ceiling is modified to include acoustic tiles. The tile has an absorption coefficient of .8 at 1000 Hz. b. What is the noise reduction, NR, after this modification? 4) An HVAC engineer needs to determine the sound reduction in a circular duct. The duct is 50 ft long and has a diameter of 36 in and is lined with 1” thick glass fiber material. At the inlet end is a fan that produces an SPL of 120 dB over all frequencies. Determine the noise reduction at the end of the duct for the 125 to 4000 Hz using Table 23-4. Plot your results in Excel. 5) An enclosure is made of 1/2-in thick gypsum board. Inside the enclosure is a noisy machine. Determine what reduction in noise will actually occur at 1000 Hz if. a) There is a 20% opening in the enclosure. b) There is a 5% opening in the enclosure....
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This note was uploaded on 02/19/2011 for the course IE 11 taught by Professor G during the Spring '11 term at Minnesota.
- Spring '11