Sound source with direction-variable beam using annular transducer array

We present a method for generating a narrow beam such that the direction of radiation is variable using an annular array. A sound source using this method has a clearance between each neighboring element of the array. These clearances are applied to decentring the array elements and the direction of radiated ultrasonic beam becomes controllable. The validity of this method is confirmed with numerical calculations, and it is shown that the beam radiated at a direction of 15 degrees from the perpendicular of the source plane still keeps the sharp profile. The sound source fabricated by this method has small, simple and planar structure, and it suggests the capability of a sound source based on this method developing into various acoustic devices.