Does ablution become void when one expels gas, even if it has no sound or smell, if the person intended to expel it?

If you are certain that wind has been emitted, then your ablution is invalidated, and you must repeat it. It is not a condition to hear a sound or to smell an odor; rather, certainty of its emission is the condition. As for mere doubt about the emission of wind, it does not invalidate ablution according to the majority of scholars.