| Popis: |
If new vehicle noise levels cannot be predicted accurately, manufacturers must overdesign for quietness in order to be sure of meeting noise standards. To determine factors affecting sound levels, nine truck–tractor configurations were tested according to SAE Standard J366b, Exterior Sound Level for Heavy Trucks and Buses during a variety of weather conditions at three, 2‐week intervals over a 6‐month period. Tests made according to the standard produce reasonably repeatable results when a vehicle is tested repeatedly at the same test site (σ≤0.83 dB). There was a statistically significant but weak effect of temperature on the A‐weighted sound level located 15 m from the center line of vehicle travel for three of nine truck test configurations, showing decreasing sound level with increasing temperature. The coefficient of this temperature effect averaged about −0.020 dB per degree Fahrenheit. Sound emission from truck–tractors was affected by temperature for eight of nine truck configurations. Humidity, b... |
