A detection area of an ultrasonic wave depends on {HEAD ~ an area} of {TAIL ~ a transmission surface} and corresponding characteristic length of the transmission surface 
of
A detection area of an ultrasonic wave depends on { HEAD ~ an area } of { TAIL ~ a transmission surface } and corresponding characteristic length of the transmission surface
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH