[hatsunearu]

That guy might have tried to say that lower frequencies cause more displacement for the same SPL, which means they necessarily go through materials a lot better.

edit: in more detail, the pressure is basically analogous to force in a fluid, and particle displacement is analogous to well, displacement, and since F=ma or F=mx'', for a given amount of pressure, the acceleration of particles stay constant, so for sinusoidal displacements you end up needing more displacement to get the same SPL for lower frequencies. And the falling sensitivity of the human ear at lower frequencies make this even more pronounced.