The method includes: selecting a first combination of transmission elements from among {HEAD ~ multiple transmission elements}, wherein {TAIL ~ the first combination} of transmission elements includes at least two transmission elements adjacent to each other; and vibrating the transmission surfaces of the first combination of transmission elements in a substantially same phase to transmit the ultrasonic wave with a first directivity 
The method includes : selecting a first combination of transmission elements from among { HEAD ~ multiple transmission elements } , wherein { TAIL ~ the first combination } of transmission elements includes at least two transmission elements adjacent to each other ; and vibrating the transmission surfaces of the first combination of transmission elements in a substantially same phase to transmit the ultrasonic wave with a first directivity
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH