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Table 2 Rail roughness limits at different speeds

From: Rail Roughness Acceptance Criterion Based on Metro Interior Noise

Speed (km/h) Rail roughness limit (dB)
All-wavelength band: 5–315 mm Sensitive band: 20–63 mm Common band: 31.5–50 mm
40 ISO +14 dB ISO +16 dB /
50 ISO +10 dB ISO +12 dB ISO +19 dB
60 ISO +7 dB ISO +8 dB ISO +12 dB
70 ISO +5 dB ISO +6 dB ISO +10 dB
80 ISO +3 dB ISO +3 dB ISO +7 dB
90 ISO +1 dB ISO +1 dB ISO +4 dB
100 ISO ISO ISO
110 ISO −2 dB ISO −2 dB ISO −3 dB
120 ISO −3 dB ISO −3 dB ISO −  dB