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Is it... No. 1 - propellant load No. 2 - turbo-pump No. 3 - lift off as heard from ground
N°3 is right. As for N°1 and N°2... You need a bit more time guessing. 
Is No. 2 a vacuum pump to remove air from the payload area in the nose cone?
No. We can safely answer that it is not. But good try. 
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The sound is unforgettable, according to people who have experienced an Ariane 5 lifting off. But this week’s question should be really easy for experts like you! 