Although phonons are commonly said to be the "particles" of sound, they are not true particles but collective vibrations of atoms in a crystalline structure. And these vibrations, which are pressure waves, can be quantized as if they were particles.
Thus, it is easy to see that a sound laser is essentially a "mechanical laser", or a mechanical analogue of an optical laser. The most efficient technique for building them is based on microspheres kept in levitation, and then shaken without contact so that their movement generates sound waves.