THE SCIENCE AND APPLICATIONS OF ACOUSTICS - H. H. Arnold ...

408 14. Machinery Noise Control(a) the number of teeth needed for the output sprocket(b) the range of output speed if input speed remains constant(c) the probable frequencies of noise and vibration due to damage to one toothor imbalance in either shaft(d) the probable frequencies due to damage to one link(e) the probable frequencies due to chordal action.14. The input speed of a chain drive is to be reduced by one-half at the output. The24-tooth input sprocket rotates at 1200 rpm. The chain contains 160 links.(a) How many teeth are needed in the output sprocket?(b) For constant input speed, determine the range of output speed.(c) Determine the likely frequencies of noise and vibration due to imbalanceof either shaft or damage to one tooth.(d) Find the possible frequencies due to damage to one link(e) Determine the possible frequencies due to chordal action.15. In a Hooke-type universal joint, in which the cross-link plane is normal to theaxis of the driving shaft, the speed ratio is given by n 2 /n 1 = 1/(cos φ), whereφ is the shaft misalignment angle, with the result that the speed range due tomisalignment is given bycos φ ≤ n 2≤ 1n 1 cos φA misalignment of 10 ◦ occurs in this type of universal joint. The input shaftrotates with a constant speed of 1200 rpm.(a) Find the speed range of the output shaft.(b) Determine the frequency resulting from vibration or noise.16. A fairly simple 3/8-inch-diameter nozzle functions under an inlet pressure of100 psi (gauge). Determine the sound level at a distance of 5 ft for an ambientair temperature of 80 ◦ F.17. A simple 25 mm nozzle operates at an inlet pressure of 600 kPa. Determinethe sound pressure level at a distance of 1.0 m at an air temperature of 20 ◦ C.18. Fifty sound level readings are taken at 10-s intervals. Find the percent exceedednoise levels L 10 , L 50 , and L 90 for the following distribution:Level [dB(A) ± 0.05]Number of Readings87 286 885 1484 1583 582 481 2