The method includes: selecting a first combination of transmission elements from among multiple transmission elements, wherein the first combination of {TAIL ~ 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 {HEAD ~ a first directivity} 
The method includes : selecting a first combination of transmission elements from among multiple transmission elements , wherein the first combination of { TAIL ~ 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 { HEAD ~ a first directivity }
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