Answer:
Helium gas, symbol He
Explanation:
The gas that causes voice to change upon inhalation is helium which belongs to the inert gas/noble gas series in the periodic table. The chemical symbol is He.
When He gas is inhaled it fills up the vocal tract and replaces some of the air present in the cavity. Now, the density of He is much lower than that of air as a result the speed of sound as it passes through the vocal cavity increases which leads to a change in voice.
