>>1946583This is a side-effect of white noise.
Radio/TV static, busy distant streets, rushing water, etc. are called "white noise", because it's like all the colors of light combined, but with sounds.
When you're hearing a constantly-randomizing range of noises over a sustained time, the part of your brain that is constantly looking for patterns starts to "find" some and tries to distinguish/memorize them, making us "notice" the sounds of certain words in the mish-mash. It's like how when you stare at stucco ceilings for a while, you start to notice "faces" in the random bumps and divets.
>>1946555Now this is a little spoooky, but it could be due to sensory deprivation.
The "voices in white noise" and "faces in stucco" effects happen because your brain basically tunes out information overload. With lack of any real pattern to find, it starts to create the pattern of either "nothing" (the noise) and "something" (the "patterns" you half-notice and half-imagine). The "nothing" parts of the information are mostly tuned out and instantly forgotten, while the "something" parts get distinguished/memorized.
Now, in the complete absence of sound/visuals, the "tuning out" job has already been done by your surroundings. With no sounds and/or complete darkness around you, there's nothing to tune out, so it becomes very easy for your brain to tell when there's "nothing" in the something-nothing pattern. However, after enough time with absolutely no information coming in for your brain to process, it becomes insanely difficult for your brain to tell when there's "something", and suddenly the sights/sounds you imagine are the closest thing your brain can call "something". You eventually have a random, distinct memory of the sound of your name, or your neighbor's face or something, and your brain goes "OH! THAT! THAT'S SOMETHING!" and it distinguishes/memorizes it, making it the only "real" thing to your brain at the time, so no matter what, you "swear you heard/saw it".
