[F14. Interpretation of results U.K.
The measurement shall be invalid if an abnormal discrepancy between the maximum value and the other values is recorded.
4.1. Determination of test result U.K.
Reference speed V ref used to determine the final result will be:
80 km/h for Class C1 and Class C2 tyres;
70 km/h for Class C3 tyres.
4.2. Regression analysis of noise measurements U.K.
The (not temperature corrected) tyre-road noise level L R in dB(A) is determined by a regression analysis according to:
where:
is the mean value of the noise levels L i , measured in dB(A):
n is the measurement number (n ≥ 16),
With
a is the slope of the regression line in dB(A):
4.3. Temperature correction U.K.
For Class C2 tyres, the final result shall be normalised to a test surface reference temperature h ref by applying a temperature correction, according to the following:
where θ is the measured test surface temperature,
For Class C1 tyres, the coefficient K is – 0,03 dB(A)/ o C when θ > θ ref and K is – 0,06 dB(A)/ o C when θ < θ ref .
For Class C2 tyres, the coefficient K is – 0,02 dB(A)/ o C
If the measured test surface temperature does not change by more than 5 o C within all measurements necessary for the determination of the sound level of one set of tyres, the temperature correction may be made only on the final reported tyre-road sound level as indicated above, utilizing the arithmetic mean value of the measured temperatures. Otherwise each measured sound level L i shall be corrected, utilizing the temperature at the time of the sound recording.
There will be no temperature correction for Class C3 tyres.
