In the last few minutes of today's meditation I started to hear/sense some sort of sound/vibration. It is a sound similar to a swishing tennis racket, with frequency of about 5 swishes/second, pretty fast, the frequency oscillates a little, the sound is deeper than the tennis racket swishing, it feels like it's heard under water. I could still hear the usual meditation background hum.
This went on for a few minutes. It was not the first time this has happened in meditation. It also happened to me on previous LSD trips.
It can be regulated at least in the way that I can "turn it off", which I didn't. It was accompannied by occasional strobo lights.
Do you know what this is? (Apart from the usual answer that it's a purification syndrome and nothing to worry about.) Anyone with the same experience?
Could it be related to some physiological process or a certain state of concentration or something like that?
