Generating amplitude acoustic patterns by mechanically shifting the emitters of an array

Acoustic patterns are employed for particle patterning, targeted therapeutic ultrasound, or 3D printing. Patterns are generated using phased-arrays that electronically control each emitter or using passive structures that modulate the wave-field. Phased-arrays can emit different patterns, but they require multi-channel electronics. Passive modulators can operate with just a single emitter but only produce one pattern and can have insertion losses. Here, we experimentally show that 2D acoustic patterns can be generated by mechanically shifting the axial displacement of individual emitters relative to the base plane in an array rather than by electronically adjusting the emission. This approach provides similar pattern quality as electronically controlling phased-arrays, it can be reconfigured and requires only a single channel. This technique is demonstrated for 40 kHz in air with a 16 × 16 array of 1 cm diameter emitters. It is an alternative to reduce the hardware complexity of phased-arrays while retaining the capability of generating different acoustic patterns.