Mapping Heavy Vehicle Noise Source Heights for Highway Noise Analysis (2017) / Chapter Skim
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7 C H A P T E R 2 Description of Measurements and Measurement Systems The acoustic measurements had three components: • Microphone array signals to be processed into noise source maps with beamforming methods, • Tire-pavement noise source levels to characterize the pavement at each measurement site, and • Statistical isolated pass-by measurements to relate to other databases. Acoustic Beamforming Measurements The beamforming measurements were made using one of the more recently developed arrays supplied by B&K, designated WL9x6D250 Foldable Wheel Array.
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Figure 2-1. B&K acoustic beamforming array setup at I-505 southbound site 505 SB2.
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Research Approach 9 Figure 2-4. Loudspeaker ~3.3ft (1m)
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10 Mapping Heavy Vehicle Noise Source Heights for Highway Noise Analysis The performance of the newer and older B&K arrays and processing for the 400 Hz band are shown in Figures 2-7 and 2-8, respectively. For the older array, the center of the spot (lightest yellow color)
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Research Approach 11 Figure 2-7. Loudspeaker ~3.3ft (1m)
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12 Mapping Heavy Vehicle Noise Source Heights for Highway Noise Analysis Figure 2-9. Loudspeaker ~3.3ft (1m)
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Research Approach 13 Figure 2-11. Photograph of data acquisition set up for acoustic beamforming measurement as installed on I-505 northbound site 505 NB1b.
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14 Mapping Heavy Vehicle Noise Source Heights for Highway Noise Analysis 25ft (7.6m) away from the centerline of the nearest lane of vehicle travel at a height of 5ft (1.5m)
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Research Approach 15 as well as subjective observations during post-processing. For the all tests, three operators were used: one to run the B&K Pulse and take notes, one to run the RTA and take photographs, and one to spot oncoming candidate vehicles for measurement and operate the radar gun and report vehicle speed.
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16 Mapping Heavy Vehicle Noise Source Heights for Highway Noise Analysis (I-505) , a four-lane interstate outside of Winters, California, with a wide median dividing the northbound and southbound traffic.
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