Emitting Surface

The sources (and sensors) for the WaveLab were developed in close collaboration with external pageProf. Michael Haberman's groupcall_made at the Walker Department of Mechanical Engineering, University of Texas at Austin. 

The emitting surface of the WaveLab consists of piezoelectric transducers mounted inside aluminium plates. The main requirements for the emitting surface can be summarized as follows:

• wide bandwidth and a frequency-independent transmit voltage response,
• uniform transmission of energy in all directions,
• small size to approximate a point source,
• mechanical decoupling of the active piezoelectric element from its waterproof housing and the plate.

A bender mode X-spring (BMX) type of piezoelectric transducer was chosen because it is known for having a low resonance frequency with compact size and high output power. The goal was to design a transducer with a resonance frequency at the lower bound of the targeted WaveLab frequency bandwidth, such that the transducer can be operated above its resonance to maximize its output power. Note that the conventional way is to operate a transducer below its resonance.

When applying a voltage at the two piezoelectric elements that make up the so-called drive stack, because the elements are poled in opposite direction with an inactive material between them, they contract and expand out of phase. The X-spring translates the resulting flexural bending of the drive stack into a vertical motion of the piston head with a magnification ratio. By carefully choosing the geometry of the X-spring, a fundamental resonance in the X-spring can be excited that is at much lower frequency than that of the drive stack.