Most probably not possible to do this remotely, since this kind of RF needs to be transmitted through the face, and if you transmit them from too far away very few of them will actually take a path that goes through the face and comes back to your receiver.

They get modulated since your mouth is a complex dielectric environment. Tissue, water, and air have different dielectric constants (different permittivity to RF) and the motion of the muscles in this medium leads to interactions with the waves that fill it, changing their phase and amplitude as they propagate.