Nowadays, the most advanced micromachined microphones on the market are represented with structures using a capacitive coupling principle. Structures and performances of these micro-devices resemble their millimetric counterparts, which are typically used as measuring microphones. In the past decade, thanks to technological progress of the microelectronics industry, microphones using a piezoelectric coupling principle have been proposed by several teams. Such novel microphones exploit the piezoelectric effect of a thin layer of aluminum nitride, which is incorporated in their diaphragm structure. In these microphones fabricated with micromachining technology, no fixed electrode is necessary, in contrast to the capacitive microphones. This specificity significantly simplifies both the design and the fabrication and opens the door for a new improvement of acoustic overload point as well as harsh environmental applications. In our contribution, we will present two most promising approaches to piezoelectric micromachined microphone design. The first approach is developed by using a flat, circular diaphragm fixed around its perimeter, having the piezoelectric layer with its upper electrode in the vicinity of the clamped region. The other approach involves a square diaphragm cut along its diagonals into four triangular beams. Such a structure enables a more compliant diaphragm compared to the first approach.