Measuring Tire-Pavement Noise at the Source (2009) / Chapter Skim
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Pages 11-16
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From page 11... ...
The site location, photographs of the pavement sections, and the average 1⁄3 octave band spectrum for each surface under baseline conditions are provided in Appendix C Measurement Protocol The baseline test condition for each test pavement and test tire followed the measurement protocol presented in Attachment 1 using "full-sized" rental vehicles along with a baseline load consisting of two people and the OBSI instrumentation.
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From page 12... ...
The microphones were calibrated using a Class I precision acoustic calibrator set for 94 dB at the beginning and end of the measurement period. OBSI quality metrics of coherence between the two microphones comprising each probe and the difference between sound pressure and sound intensity level were monitored during data acquisition.
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From page 13... ...
The Dunlop tire baseline measurements conducted prior to 8:30 am were not included because similar early morning measurements were not conducted with the SRTT. The Dunlop tire resulted in overall sound intensity levels that were 2.2 and 1.9 dB higher than the SRTT levels for the AC and PCC pavements, respectively, with an average difference of 2.0 dB.
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From page 14... ...
Over the day of testing at MnROAD, air temperature ranged from about 66.2°F to 74.3°F for the baseline configurations and pavement temperature varied from 79.9°F to 107.2°F for the AC pavement and from 78.1°F to 98.6°F for the PCC pavement. The temperature fluctuation throughout the day in Mesa was greater than that in Minnesota and, unlike the MnROADs testing, the baselines at the DPG were acquired over multiple days.
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From page 15... ...
As tire inflation pressure increases, 1⁄3 octave band levels below 1,000 Hz decrease and levels above 1,000 Hz increase, resulting in small overall changes to the sound intensity level (0 to 0.5 dB increase per 10 psi increase) as shown in Figure 11.
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From page 16... ...
Data Quality Criteria During the data acquisition, the coherence between the signals from the two microphones comprising each probe and the difference between sound pressure and sound intensity level (PI Index) were monitored and recorded for each 1⁄3 octave band.
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