If I may add the two cents accredited one of our more recently departed hero scientists, Prof. Persinger.
He was doing tests where two special helmets produced matching frequency "patterns" and one of the many things they found was a synchronized sharing of data between brains from a distance. Very quantum in that the results showed there was no conduit, no here or there, and many other very cool things. Add that we know how the brain reacts when you "deprive" it of sensation, thus the earplugs blocking sound. Think of the "Sensory Deprivation" tank therapy.
So, IF it was happening for similar reasons, then you are encouraging the mind to find stimuli by blocking it with ear plugs, and then synchronizing at the right frequency pattern with anything external and processing that data through your sensory system as sound. From my own experiences, I have found that the data is sometimes "off" in time, or wobbles through time. So you get this peaks and valleys of voices or music, or twirling repeats like pool eddys. I have found that time differences challenge the frontal lobes and the ego, so be careful trying to think about that for too long.
BTW I call this "listening". For me it is similar to listening for a faint noise among many other noises. Voices begin to sound like they are coming through a metal tube. Time echoes make things overlap.
So, if you have similar experiences, science is getting closer to seeing it, and trying to describe it, how it is possible, etc.
Brain Synchronization | Dr. Michael Persinger