例一 频率 10~500 Hz
Hz PSD
10 0.02
500 0.02
A = (f2-f1)×PSD
= (500-10)×0.02
= 9.8
Grms = √A
= √9.8
= 3.13 Grms
例二 频率 20~2000 Hz
Hz PSD SLOPE
20 3dB/Oct
80 0.04
350 0.04
2000 -3dB/Oct
A = [(3×S2)/(3+X)]×[f2-((f1/f2)×f1)] 备注︰（3为常数，X为斜率）
= [(3×0.04)/(3+3)]×[80-((20/80)×20)]
= [0.12/6]×[80-5]
= [0.02]×[75]
= 1.5
B = [f3-f2]×PSD
= [350-80]×[0.04]
= 10.8
C = [2.3×S3×f3]×[log f4/f3] 备注︰（2.3为常数）
= [2.3×0.04×350]×[log 2000/350]
= 32.2×0.7569
= 24.37
Grms = √(A+B+C)
= √(1.5+10.8+24.37)
= √36.67
= 6.055 Grms
