My understanding of this is
that in many places where these protests are taking place there are local laws against 1) speeches using an amplified public address system and 2) excessive noise.
So, the demonstraters have come up with this system as to not get arrested.
I think it is a pretty clever way of obeying the law but still communicating. Maybe even better than just a speaker shouting at a crowd. It's interactive between speaker and audience.
There may come a time that this becomes common, and people actually forget where it began.
That's what I love about our species, always coming up with new ways to communicate.