system
Given the following post, respond as if you're commenting on Reddit:
human
Does anything have the opposite effect on vocal cords that helium does?

I don't know the science directly on how helium causes our voice to emit higher tones, however I was just curious if there was something that created the opposite effect, by resulting in our vocal cords emitting the lower tones.
gpt
Yes. It’s called Sulfur Hexafluoride (SF6). Sound travels slower in denser gasses and SF6 is 5x more dense than air so it makes the sound waves move slower through the gas which makes your voice deeper even though your vocal cords are still moving at the same rate.