A phonon is a collective excitation that shuttles heat around solids, and herds electrons into the coherence that affords superconductivity. Just as plasmons are quantized plasma oscillations, phonons are quanta of mechanical vibrations.
Phonons are not actually real. They are really just a way of simplifying a very complicated problem. ~ English physicist Jon Goff
As sound is a mechanical vibration, it quantizes as phonons. Sound waves have negative effective gravitational mass.
A sound wave not only is affected by gravity but also generates a tiny gravitational field. ~ Italian physicist Alberto Nicolis