Suppose we have two source of disturbance to produce sound waves. The intensity of sound produced by the first source at P is I1, and the other intensity is I2. So what is the intensity at point P. I see many books saying that I=I1+I2. Can you explain why? net medium displacement vector s=vector s1+vector s2 we have I=(1/2).p.v.(w.Sm)^2 p is the density of medium, v is sound speed, Sm is displacement amplitude of s yet I1=(1/2).p.v.(w.S1m)^2, I2 =(1/2).p.v.(w.S2m)^2 obviously I doesn't equal to I1+I2 !!! Thank you.