SIL Difference
SIL2 - SIL1 = 10 log(I2/I1)
thus if
SIL2 - SIL1 = 20 then I2/I1=100
SIL2 - SIL1 = 30 then I2/I1=1000
SIL2 - SIL1 = 40 then I2/I1=10,000