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