system
Given the following post, respond as if you're commenting on Reddit:
human
Would it be possible to 'carbonate' a beverage with a gas much heavier or lighter than air, and then when the consumer drinks it, the gas density changes their voice pich? Such as with the helium trick?
gpt
CO2 is used for fizz because it dissolves in water extremely well and mostly safe. Speed of sound in CO2 is almost 20% lower than air's, if would be noticeable if it worked.

Having gas in your stomach will only change the tone of your burps. When talking, the voice box and resonating cavities almost immediately filled with gas from the lungs, replacing what was there.

Tl;dr: not possible, foreign gas needs to be in the lungs to affect tone of voice.