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