Variation in On-Board Sound Intensity Levels Created by Different ASTM Standard Reference Test Tires

Variation in tire-pavement noise levels produced by different ASTM Standard Reference Test Tires (SRTT) on ten different test track pavements was investigated using the on-board sound intensity method as a portion of the NCHRP 1-44 (1) Project, Measuring Tire-Pavement Noise at the Source: Precision and Bias. The measurements included eleven new SRTTs and six older, in-service tires. Ten different pavements were used in this evaluation including eight asphalt and two concrete test sections. The average of the ranges in level for the new tires as measured on the ten pavements was found to be 1.1 dB. In comparison, the average of ranges for a single tire tested multiple times was 0.7 dB. The six in-service tires produced a smaller average of ranges of 0.9 dB, however, when older and newer tires are considered together, the average increased to 1.6 dB. As groups, the older tires were found to produce levels 0.5 dB higher than the new tires on average. The older tires had higher tread rubber durometer hardness values than the new tires, however, within each group, consistent trends could not be identified. After nine months, the original new tires were retested. Some of the tires were subjected to mileage accumulation, accelerated aging, and wheel width changes. It was found that the effect of tire aging variables including hardness, tread depth, time since construction, and mileage, were not necessarily consistent from tire-to-tire. However, considering the extremes of durometer hardness, reduced tread depth, accumulated mileage, and in-service years, a proposed strategy for retiring test tires based on a combination of these factors is advanced.