The first directivity is different from {TAIL ~ a second directivity} of {HEAD ~ the ultrasonic wave} transmitted from single transmission element 
The first directivity is different from { TAIL ~ a second directivity } of { HEAD ~ the ultrasonic wave } transmitted from single transmission element
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH