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