You are following perhaps half the conversation. Music, nearby voices and the room's general noise keep covering the ends of sentences. You nod because asking for the third repetition feels more awkward than missing the point.
Name the practical problem. “I am having trouble hearing in here. Could we move somewhere quieter?” gives the other person information and a possible solution. It does not require an explanation of your hearing, attention or personal history.
Look for an appropriate alternative that works for everyone. A quieter table, a different part of the venue or another time may be possible. Do not assume that stepping outside is accessible, comfortable or private for the other person; ask rather than simply leading them away.
If the discussion is sensitive, consider privacy as well as noise. A quiet corridor is not necessarily a confidential place. It may be better to arrange a separate conversation rather than trying to solve the setting while an important subject is already unfolding.
You can ask for a sentence to be repeated or rephrased while you work out the arrangement. Guessing can create misunderstandings that are much more awkward to repair later, particularly when plans or responsibilities are being discussed.
If moving is not possible, acknowledge the limitation and decide whether to continue. You do not have to keep pretending the conversation is working merely because everybody else seems comfortable with the room.
Name the practical difficulty without blaming the people around you. “I am missing some of what you are saying; could we move over there?” directs attention toward a solution. Check that the proposed spot is accessible and comfortable for the other person too. A quieter corner is not automatically suitable if it is cramped, isolated or inconvenient in a different way.
Sometimes moving is not possible. You can suggest continuing later or using another suitable way to exchange the important detail. If the conversation is private, avoid raising your voice simply to compete with the room. It is reasonable to protect both understanding and discretion. Making that choice early may save you from spending an entire meeting nodding along while hoping nothing crucial has been lost in the background noise.
The request can benefit the other person too. They may also be straining to hear, or may have assumed your quieter participation reflected a lack of interest. A change of setting makes the actual problem visible. Sometimes being more present in a conversation begins with asking for a place where the words can reach you properly, rather than making another effort to appear effortlessly sociable in unsuitable conditions.
A little more room to be yourself.