I was recalling how when more than 20 people cahnting bhuddist sutras a pecukiar crackling noise fills the air. I have recorded this phenomenon a number of times since it is picked up by the microphone. When it is happening however the sound seems to come from inside your own ears.

Has anyone ever noticed this eithier in chanting, prayer or choral situations?
I suppose there is a scientific explanation but even a BS one would dl :)