Because of its narcotic effect at high pressure, nitrogen shouldn’t be breathed by humans at depths below about 60 meters. So, at 200 meters, the breathing mix in the habitat will be 2 percent oxygen and 98 percent helium. But because of its very high thermal conductivity, “we need to heat helium to 31–32 °C to get a normal 21–22 °C internal temperature environment,”
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So everyone is gonna sound like mice when they get crushed under the weight of the ocean?
Hmm… maybe not? The low density of helium at 1 atm is what causes the amplification of higher frequencies in the voicebox, but in a pressurized container the gas would be higher density so it might offset the effect… I think?
If the original SeaLab tests in the 60s were any indication, YES. Check out Scott Carpenter’s voice on this recording with LBJ. https://www.dailymotion.com/video/x3wkh6s
Apparently when doing saturation diving like that you can’t even understand what the other person says, between the helium and the pressure the voice is too distorted to be intelligible.
You can communicate with a computer that transforms your voice to be intelligible but it is really not a pleasant conversation so you can stay there for weeks without having a conversation except for the bare minimum.
