[carlbarrdahl]

I'm sure there are differences in their effectiveness.

Based on my limited knowledge the sound frequencies attempt to put the brain into theta or delta frequencies and does this by creating a ghost signal (left ear 100hz - right 106hz gives a 6hz theta wave).

Dreamachines work similarly (but mono) by creating a flickering light at set frequencies.

I'm sure tactile vibrations or pulses could have some effect also.

[numtel]

I made this a few years ago after getting into Hemi Sync tapes to test out what different tones feel like.

https://numtel.github.io/binaural-playground/