Part Ca: External noise grading The external rolling noise class must be determined on the basis of decibels (dB(A)) according to the scale specified below: External rolling noise classes (dB(A)) Colour code C1 C2 C3 Green ≤68 ≤69 ≤70 Yellow 68≤dB(A)≤70 69≤dB(A)≤72 70≤dB(A)≤73 Red ≥70 ≥72 ≥73