D=10 log (P1/P2) Where the values of P1 and P2 are expressed in the same units, such as watts (w). If P2 = 75 w, find the value of P1 at which D=0.7 Solution D = 10 log ( P1 / P2 ) P2 = 75 D = 0.7 0.7 = 10 log ( P1 / 75 ) dividing both sides by 10 0.7 / 10 = log ( P1 / 75 ) 0.07 = log ( P1 / 75 ) 10^0.07 = P1 /75 P1 = 10^0.07* 75 P1 = 88.12.