“…Transfer path analysis (TPA) has been proposed to obtain the contribution quantitatively and several methods were developed until now (Plunt, 1998;Noumura, 2006;Brandl, 2008;Lohrmann, 2008;Klerk, D., 2010;Putner, 2012). Operational TPA (OTPA) is one of the methods recently developed and enable us to obtain the contribution of each part (reference point) to the response point with small man-hour because the method calculates the contribution using only the sound and vibration signals at the operational condition (Noumura, 2006;Lohrmann, 2008;Klerk, D., 2010;Putner, 2012;Yoshida, 2016;Yoshida, 2017;Hirao, 2019). For applying the method, all reference and response point signals are necessary to be measured simultaneously since the method calculates the contribution from the relationship between reference and the response signals along time.…”