According to Krichevsky when a person speaks, the sound that comes out will shoot out and eventually bend upward to the sky. Sound is known to move faster through a denser media than a less-dense media, therefore, speed of sound above a phonon will be lower than a slightly denser particle below it. If this is true, sound can be thought of a a negative gravity.
The paper also states that the effect is so small it cannot be measuring with technology. As scientists look deeper into this new theory of sound, a precise measurement tool could be made to detect the curvature of the phonons path. This paper has changed the perception of sound and how it interacts with the environment. As more data arises, we will know the true nature of sound. So now we wait to see if sound really is like negative gravity.