A numerical investigation of the nearfield region of a vibrating piston was conducted. While existing literature is not exactly clear about how close to a transducer a regular beam pattern is formed, the results of this investigation show the limits of operation one can expect. From one interpretation of literature, a −3‐dB beam with a minimum spot size equal to the transducer diameter would be expected to form beyond an axial distancez= 3.89a2/λ. This investigation shows that such a beam forms atz= 0.75a2/λ and has a minimum spot size equal to one‐quarter the transducer radius. These results are verified for transducers witha/λ's ranging from 1 to 20 and can be extended with confidence to highera/λ's. Similar results are also obtained for −1.5‐, −4.5‐, −6.0‐, −7.5‐, −9.0‐, −10.5‐, and −12‐dB beams.