Forgive making up words up to express.
Q: "What was the significance of the symbols?"
My opinion:
The brain organizes information neuro-graphically. Pictographic-ally referencing connections between dendrites & other associative pathways interconnecting relevance between language, thought, association, time, and recall sorting based upon associative cognitive state.
This is encoded upon time of imprintation, interpolation, and significance placing neurological chemical marker for bridging other constructs fractally like a directory structure 3 dimensionally.
This is observed outside our brains ability to normally process visual data (In how we see in the real world opposed to in our head where data is more tightly dimensionally knotted).
This information visualized by the spatial visual cortex on your brains internal "chalkboard" (imagination) angles into glyph symbolic mathematical architecture congruent with relevancy towards the internal mental construct hierarchy.
This is relevant again to a "systems approach" mental marker "geometrical shape sorting system" where you see shapes showing construct; similar to brain "mind mapping" software helping us most efficiently evolve path of least resistance towards a the most efficient (process & concept) / (evolution/sorting) visualization we can utilize for conveying concepts more clearly person to person in real life.
This internal automatic model relates the relevancy of right brain hemisphere landscape, shape/information recall information into intuitive insight gleaned in normal awareness. I believe our brains intuited this neurological evolution thanks to the frontal lobe.
Genetic inheritance of this adaptation was due to homo-sapien's survival hinging upon our language, shape, time sorting, recall, + ability to predict immediate future.
Consider brain function not normally noticed in normal state of consciousness behind this veil as pure internal language evolved from how well each person's been able to grow in their own brain since birth their own sorting system. Children subjected to fractal zoom video, mind mapping concept based visualization, hierarchical sorting, logic classes in the future may have more intricate fractal visualizations partially from will and intent creating a co-creative synonymous link between the conscious and subconscious construct; the imaginative chalkboard with neuro-chemical architecture finally able to see internal processing of their own brains without the help of DMT like a chemical marker for observance of consciousness's synthesis processes.
This "glyph symbolic mathematical architecture" is relevant to recall assuring real-time automatic subconscious navigation of the brains internal access points.
Significance is your deal when you experienced the process of automatic sorting of ideas, novel concepts, and experiences at the time of experiencing them. Analogous to the "Meaning of life is what you make it/nothing" significance explanation however the right brain compartmentalizes paradoxes handed to it over a lifetime and then expounds upon them fractally subliminally into chopped up meaning and relevance gleaned from lucid mind-states or within contextual dream awareness (recall) states as one drifts back into conscious awareness finds pieces and meaning of dream data sometimes sorted outside of a progressive time frame function. Working the relevance or significance of what sees internally upon tryptamine consciousness, between paradox compartmentalization perspective .
Symbolic construct lends to directions inside ones own head. Write down the symbols, relax, release, and re-engage consciousness but before you come back to focus, imagine imprinting the symbol in the center of your peripheral view the symbol indirectly asking ones self; "what direction does this lead me towards?". Listen to the automatic direction flowing often subtle direction symbolic shape references as a feeling of meaning or interconnectedness. Notice the flashes of pictures in your head.
If you don't get anything, practice with well known iconographs like Crosses, Star of David, etc & let flow state bring you to where you can subtly notice your own internal pictorial associations. In context to internal structure, I see similarity associatively how archetypes and memes are made of several referenc(ing,ed,) (I'll invent word: "referencial"
associations collectively in how the brain sums up concepts in order to give them structural meaning and relevance we can understand consciously (How "god" illogically cannot be understood as a concept, but has arrows pointing towards it or a general direction, direction for approach) but throw all that un-referencable information into a trash can sum it up best approach we can at understanding self concept for higher mind in a word that helps us conceptualize "function orientation" / epitaph without getting too much information causing cortical overload, brain dump shutdown forgetting where we were going, what we were trying to remember, or what we were thinking about like a lofty excuse to sun surf / drift consciousness in order to linguistically harness the power of metaphor.
Thoughts Drifted into god : ->
.. to infer "god" into conceptual shape that can be conveyed with relative meaning to another persons internal visual conceptual understanding / motif representation to "god". With "god" being outside one's self concept, so loose a thing for interpritation the statistical chance of error when contextualizing "god" concept between two brains must be one of the most flawed illogical attempts at a "logical" underpinning of intrinsic concept to infer. No wonder we have so many misunderstandings trying to convey higher self concept through our "version" of what god means to us, variation there in multiplying by times squared the chance for being misunderstood, I can see how frustration arising from this would lead one to fight another out of frustration due to a gross failure to communicate binded by indifference arising from such deeply seeded differences in self concept arising into two completely different senses of "false self" / ego would be the spawning grounds for ego contention where two people with different concepts of god would seem to never be able to agree on anything.
Back on track: ->
If your brain's too tightly wired to access this due to being overly constipated in logic, analytical mind-state, too dismissive of ones own intuition, perhaps self hypnosis could help one.
It's a magic trick sometimes how irrespective how we never in normal awareness consciously imprinted meaning upon shapes our subconscious construct has already automatically over written our own ability to have desire or inclination to logically use symbolic morphology for recall, but our brains do it automatically like a "dirty secret" to keep the mind from gleaning insight into how our brain's right hemisphere really works.
Q: "What was that noise, and why do so many people experience it?"
My Opinion so far:
There are four basic categories of brain waves: Beta, Alpha, Theta and Delta each changing states of conscious function and recall having octaves 7 tones embedded inside of 7 sub-octave tones spirally flowing scoping down into each other fractally visually sorting sound and sight from most relevant sense (aside awareness itself) externally into internal sorting of this data visually/acoustically where this "noise" (DMT carrier wave) can be a tool used to remember how to zoom down to and recall virtually anything you've experiences associatively from the time of your birth to the here and now (visually seen during dissociative trips / NDE / as what I call the "dissociative spiral". Try zooming down into it and you see pictures of memories. In NDE can be television sets recounting memories over surface of orbs as you cruise over top of them recanting lifetimes experience.
Tinnitus ringing's the disconnection of the mirror neurons for sound disconnecting from loci of "what you're hearing out loud in the room while tripping" acoustically amplifying feedback (like mic feedback) from consciousness's normal inaudible background hum into an overwhelming internal "sound in one's head" pulling you into all directions automatically into a non-associative state seeing outside of any single brain-state (like being "in" alpha mind-state for example). This infers all (Beta, Alpha, Theta and Delta) states are going on all the time. We can't normally hear the brains natural acoustic spatial multiplexing.
Pre-cursive to "liberation from normal consciousness" experienced earlier on in the process of a higher dosage range DMT trip.
Perhaps so many people experience this due to similarities in how what evolved for interacting with the outside world necessitates sorting systems where what you hear and see are interconnected by awareness states to signal sleep, dream, awareness, loose awareness, and heightened awareness, and survival related information from past events would have to be sorted by mind state experienced during said experience of the organism were to continue to survive multiple life endangering experiences. Evolution-ally sleep cycle brain state normalized into healing the body for survival. Relaxed states allowed lowering metabolism, etc.
Sparing how all inherited via what worked translated into how we got to what we are, I can see that irrespective one's gross lifetime experiences environment, DNA, biology, and similarities there in should be self explanatory as to why so many experience this "noise"; hence dreams being the wasteland of unsorted novel information of importance metaphorical contextually how "god" is a dream referenced "wake from the dream of religion to see reality for what it is", DMT wakes one from consciousness and dream (God) into the sum totality of being outside of space and time (expansion of consciousness to void, time dilation to infinity, and evolution of self concept responsible for the trend where i see the gradual evolution of highly intellectual / knowledgeable spiritual "theist" apologists turning atheist after a godhead / unitive experience brought on due to a high dose freebase DMT experience.
I believe flickering of symbol and shape is due to DMT's constant activation of serotonin receptor sites opposed to what we see in scientific observation of serotonin neurotransmission. Cutting off parts of the brain from each other, cutting off sensory input, and disrupting electrical activity in the brain can all cause flashing of light. Perhaps disruption of the occipital alpha rhythm or interrupting normal pulses from the front to rear of the brain cause similar disruption. Perhaps it's purely related to a physiological bio-electrical capacitance of energy, and then a release of that energy resulting in the perception of the flashing in & fading out effect. I don't know.
I= SWIM = Not Me. The I AM I Does Not Exist, and is Referenced to SWIM Who Is Not A Friend I Never Met, Nor Hallucinated While Imagining The Is-ness of Suchness That Is SWIM Who Is Not Me, Myself, Nor I As The Expression Of Non Dual Aspect of Non-Dual Reality Subjectively Denied By Swim, or accompanying Me-Anti-ness'es. =) All Credit Goes To The ANTI-SWIM'ness of SWIM's cousin's room-mate's uncle's deceased cat's in-law's second removed nephew's aunt WHOM authored SWIM's 2000 Year Old Desert Scribblings from a drunk rabbit in the Serengeti desert found in an insane asylum under water, on Easter eggs, crucified by the on fire pagan music listening christian maniac from India running around believing he was Jesus repenting this bush he called the Acacia tree; So I Heard from a bum who claims to be SWIM, But I Forgot... And Again, "I" Refers To Someone Who Is Not Me.