So I have a question I am hoping someone can help me answer. I am trying to compute transfer functions for a hammer impact with an accelerometer response on a cylinder. Please see the attached photo. http://imgur.com/F8DGwl2 For some reason the picture did not attach but I have uploaded to Imgur: http://imgur.com/F8DGwl2 I have a transient impact of a hammer at F1 on a block protruding from the face of the cylinder. Then I can compute a transfer function from the hammer impact to the accelerometer response a1. I do the same then as a separate run for another hammer impact, this time of F2 at a different location. Because I am assuming it is a linear system, F3 can be defined as F1+F2 but I am unsure if this works for a transient case. I understand if both F1 and F2 were hit at the same time that F3=F1+F2 but I don't know if those holds true when they are hit at different times. Ultimately, I would like to know if there is a way that I can sum up the two transfer functions (f1 to a1 and f2 to a2) and result in the same transfer function as if I were to hit with F3 at a different location to a1.