Separate two acoustical waves

I did a measurement in the acoustical lab to detect a range of a target by using continues acoustical chirps

i used speaker as transmitter and two microphones to record the transmitted and reflected sound signals at the same time to achieve the sync between them.

to do the analysis i have to multiply tow signals to get the shifted frequency.

receiver's microphone had been received the reflected signal and an effection from transmitter(speaker)

how can i remove this effection?