Vibrating sensation whilst Mediating.

[anagogy]

I think they might be a higher subdensity of 3D. I don't think we can feel 4D energies with a 3D body, unless you have a hybrid body (are 3D/4D soul).

Every body acts like a filter for the octave of energies. There is a certain amount of energy from every level of density that you can feel in any activated body, depending on your level of allowing. The subdensities of a given density are the portion of that true color density's energy that can be felt in one's current density. So you can feel 4D energy in 3D, however, you can feel more 4D energy in 4D, because the limitations on that activated body are more allowing of those energies. You can draw on the whole spectrum of energies, but they are filtered through the lens of your current reality/density.