Acoustic detection is a promising technique for the detection of Ultra High Energy (UHE) neutrinos. It is based on the detection of the short bipolar pressure pulse with very directive pattern (pancake) generated after the neutrino interaction with a nucleus of the water. The acoustic sensors could be implemented in the optical-based deep-sea neutrino telescope under construction (KM3NeT telescope), working then as a complementary hybrid detector. Acoustic emitters able to imitate the signal are needed to calibrate the sensors and to study the viability of the technique. For this purpose, a compact calibrator composed of few piezo-ceramic transducers emitting in axial direction and structured in an array system has been designed. The array is operated at high-frequency (hundreds of kHz) and, by means of the parametric effect, the emission of the low-frequency (tens of kHz) acoustic bipolar pulse is generated permitting to mimic the UHE neutrino acoustic pulse. Electronics have been developed as well for the signal amplification to assure the power needed and for the control operation and monitoring of the emitter. In this paper, the design, development and characterization of the acoustic array emitter is presented, showing the results obtained in the involved processes, such as, parametric emission studies, ceramic design optimization through backing and heading, electronics design, multi-element array design and tests in the lab and for long distances in the sea.