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Lumifer comments on Stupid Questions, December 2015 - Less Wrong Discussion
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Why can I hear noise (white noise / pink noise / brown noise), but not hear temperatures?
EDIT FOR CLARIFICATION Air temperature is caused by air molecules moving randomly at high speed, white noise is caused by air molecules moving randomly at high speed, what's the difference? Why does white noise fill the room with sound instead of just raising the temperature slightly?
My hand-wavy-sounds-like-science-technobable guess is that temperature does fill the air with sound, but most of the energy of that sound is at far too high frequencies for my eardrums to detect (in part because my eardrums are emitting noise at a those frequencies). Maybe the average wavelength of thermal noise is roughly the mean free path length of the air molecules, so the average frequency of the noise is roughly 5 GHz. But I just making stuff up and really don't know.
This is wrong. What you hear is sound waves, that is, rarefaction/compression zones in the air, pressure differentials. They are a phenomenon at a different scale than molecules. In particular, the energy involved is different. "White noise" means the frequencies are uniformly distributed.
Essentially, an air molecule doesn't have enough energy to register at your hearing sensors, that is, to move your eardrum (or cochlear hairs).
Though, now that I'm thinking about it, if the white noise generator I bought to help me sleep is really good at producing white noise with uniform power at high enough frequencies, an air molecule would have enough energy to move my eardrums. I would also be on fire.
And if my white noise generator is really really good at producing white noise with power uniform across all frequencies, the noise's mass-energy will cause my bedroom to collapse into a black hole and I will be unable to leave a 5 star review on Amazon.
Yes white noise is an ideal that can never be realized in reality, like a perfectly rigid object, or a frictionless wheel, or an absolute zero freezer. White noise would carry infinite power.