1. The problem statement, all variables and given/known data I thought that only the length that the sound travels affects the pitch. However, in low pressures/breathing helium the distance traveled by the gas is the same so how is pitch affected? 2. Relevant equations none 3. The attempt at a solution this is what i found from another post "That's true, but the atmospheric pressure has as much to do with propagation of the sound as the pitch. The frequency is primarily determined by the length of the vocal chords; the longer they are, the lower the frequency. Thinner air, though, absorbs the energy of the sound before it can go very far. That's the reason that people sound so 'duckish' after inhaling helium. The change of ambient gas density effectively (but not physically) shortens the chords. That is because the initial vibrations are attenuated according to the density of the medium that they are propogating through." I don't understand how thin air can absorb more energy than normal air and how does decreasing the energy decreases the pitch shouldn't it only decrease the loudness since there is less energy? Thanks for the help!