Measuring Tire-Pavement Noise at the Source (2009) / Chapter Skim
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From page 17... ...
statistical passbys of both light- and heavy-duty vehicles on in-service payments. Using the SPB data, the relationship between OBSI tire-pavement noise and average vehicle noise emissions was examined for both light vehicles and heavy trucks.
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Three passes were made for each test speed, which were averaged together during post analysis. During the data acquisition, OBSI quality metrics of coherence between the two microphones comprising each probe and the difference between sound pressure and sound intensity level were monitored.
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Light Vehicles Heavy Trucks 25 ft Microphone Distance 50 ft Microphone Distance 25 ft Microphone Distance 50 ft Microphone Distance Site # # of Events Speed Range (mph) # of Events Speed Range (mph)
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. Normalized SPB and CPB Data versus OBSI In order to demonstrate the applicability of the OBSI data to in-service pavements, a series of cross-plots were considered in which the relationships between OBSI and the passby data could be quantified.
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From page 21... ...
In this plot, any site bias is effectively cancelled out leaving only the ability of the test tire to replicate the behavior of the SPB data that spans many different tires and other light vehicles. Figure 14.
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From page 22... ...
25 ft Microphone Distance 50 ft Microphone Distance SRTT Dunlop SRTT Dunlop Cross-Plot Metrics Raw Norm Raw Norm Raw Norm Raw Norm Slope 1.31 1.06 1.17 0.95 1.41 0.97 1.38 0.97 r 2 0.91 0.96 0.85 0.94 0.86 0.96 0.86 0.96 Offset, dB 24.3 24.2 24.8 24.7 31.4 31.0 31.7 31.3 Std Dev, dB 1.4 0.6 1.4 0.6 1.9 0.6 2.0 0.5 Avg Dev, dB 1.1 0.6 1.1 0.5 1.6 0.4 1.6 0.4 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 102 104 106 108 110 OBSI Level, dBA So un d Pr es su re L ev el , d BA US 30 BD US 30 TT US 30 UT US 30 AC US 30 LT LA138 S1 LA138 S2 LA138 S4 LA138 S5 Moj S1 Moj S2 Redding 1-to-1 Line Linear (21.9 dB offset) 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 102 104 106 108 110 OBSI Level, dBA So un d Pr es su re L ev el , d BA US 30 BD US 30 TT US 30 UT US 30 AC US 30 LT LA138 S1 LA138 S2 LA138 S4 LA138 S5 Moj S1 Moj S2 Reddin g 1-to-1 Fi t Linear (21.8 dB offset)
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From page 23... ...
However, as with the light vehicles, normalizing the SPB data produced a reduction in the deviations about the 1-to-1 line with minimal change in offset for each microphone distance and test tire. Cross-plots of the SPB versus OBSI data for the SRTT measured at 25 ft are shown in Figures 19 and 20 for the raw and normalized data, respectively.
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From page 24... ...
25 ft Microphone Distance 50 ft Microphone Distance Cross-Plot Metrics SRTT Dunlop SRTT Dunlop Slope 0.94 1.02 0.92 0.94 r2 0.93 0.96 0.94 0.96 Offset, dB 2.7 1.0 2.6 1.1 Std Dev, dB 0.9 0.7 1.0 0.8 Avg Dev, dB 0.7 0.6 0.7 0.7 80 82 84 86 88 90 92 94 96 98 10 0 96 98 100 102 104 10 6 1 08 11 0 1 12 114 116 OBSI Level, dBA So un d Pr es su re L ev el , d BA PCC 1 PCC 2 PCC 3 AC 4 PCC 5 AC 6 AC 7 AC 8 AC 9 PCC 10 PCC 11 AC 12 1-to-1 Line Linear (12.9 dB offset) 80 82 84 86 88 90 92 94 96 98 100 96 98 100 102 104 106 108 110 112 114 116 OBSI Level, dBA So un d Pr es su re L ev el , d BA PCC 1 PCC 2 PCC 3 AC 4 PCC 5 AC 6 AC 7 AC 8 AC 9 PCC 10 PCC 11 AC 12 1-to-1 Line Linear (12.9 dB offset)
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From page 25... ...
Depending on which offset is selected, the SPB levels for light vehicles or trucks at 25 ft or 50 ft can be predicted. Further, the predicted SPB levels can be compared to both the raw and normalized SPB levels.
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Figure 23. Predicted SPB based on SRTT and Dunlop tires and measured light vehicle SPB levels at 60 mph and 50 ft -- raw and normalized.
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From page 27... ...
In regard to truck SPB results, no evidence was found to suggest that the more aggressive tread of the Dunlop tire would better represent truck SPB variation with pavement than would the SRTT. Since the two tires performed equally well in producing predicted SPB levels for both light vehicles and heavy trucks, the decision on which test tire to be used in the OBSI procedure can be based on other, non-noise related issues (e.g., long-term availability)
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From page 28... ...
where engine/exhaust noise are expected to become more pronounced. However, the ability to predict SPB levels for heavy trucks from OBSI data alone was almost equal to that for light vehicles.
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