From a physics perspective, sound is waves of vibration moving through matter, whether through air, water or a solid. The “dreaming mind” may exist at higher vibrational levels, such as in the etheric body or “astral bodies.” There are undoubtedly higher frequency subtle vibrations that move through those levels.
“Pink noise”, however, may effect the brain at the physical level and the brainwaves of sleep. Lots of “subtle” distinctions here.
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