5. Three small fans are located near each other at 1.5 m above the ground, and produce an annoying noise in the 250 Hz band. A local resident whose bedroom window is at the same height as the fans and is 80 m away complains about this noise. Measurements indicate that noise levels in the 250 Hz band at 2 m from each fan are 85 dB, 92 dB, and 91 dB respectively. a. Calculate the total level from the three fans at the window. (Note that you do not need to A-weight anything in this problem) b. A noise control barrier is to be located 3 m from the fans, and must reduce the 250 Hz fan noise to 55 dB outside the neighbor's window. Measured from ground level, how tall must the barrier be?

5. Three small fans are located near each other at 1.5 m above the ground, and produce an annoying noise in the 250 Hz band. A local resident whose bedroom window is at the same height as the fans and is 80 m away complains about this noise. Measurements indicate that noise levels in the 250 Hz band at 2 m from each fan are 85 dB, 92 dB, and 91 dB respectively. a. Calculate the total level from the three fans at the window. (Note that you do not need to A-weight anything in this problem) b. A noise control barrier is to be located 3 m from the fans, and must reduce the 250 Hz fan noise to 55 dB outside the neighbor's window. Measured from ground level, how tall must the barrier be?