2.1 Properties of signal and Noise Decibel(db this is a base 10 logarithmic measure of a power ratios, for a circuit, O 10 lo average power out s10 out dB/10 dB=10logp average power in /R dB= 10 log rms out out 2 /R rns In -dB=20 log ms-ou +10log Rim or dB-20l0g ms-ou +10 log Rou rs-In Ims-In Rn In Engineering practice dB=20 logl rms-out rms-out 10 rs-ln rms-In10 2.1 Properties of signal and Noise • Decibel(dB) this is a base 10 logarithmic measure of power ratios, for a circuit,         =         = power in power out 10 log 10 log average average P P dB i n out         = rms i n i n rms out out V R V R dB / / 10 log 2 _ 2 _         +         =         +         = − − − − i n out rms i n rms out out i n rms i n rms out R R I I dB R R V V dB 20 log 10 log or 20 log 10 log /10 10dB in out P P  = • In Engineering Practice:         =         = − − − − rms i n rms out rms i n rms out I I V V dB 20 log 20 log