One of the witnesses did not hear the acceptance (qabul) clearly because it was noisy. Does the contract need to be repeated?

Yes; if a witness did not hear the offer or acceptance clearly, the marriage officiant will usually ask for the words to be repeated in a quieter setting. There is nothing shameful in this. Repeating shows care, not a failure on the couple's part. Avoid this problem by asking guests to be quiet when the contract begins, turning down the music and providing a microphone if the space is large. Witnesses should also have the courage to speak up if they are unsure, not just nod. If doubt arises after the ceremony is over, consult the marriage officer at the religious office and do not draw your own conclusions. See a qabul that falters.