MFL wrote:
OP does not give any info, age, brand of AC, trailer make, but not much sound proofing to be done.
Since the OP hasn't provided any information about A/C make / model nor trailer make / model that also raises the question as to whether this is a direct blow A/C or a ducted system. Having owned both I'd suggest that a ducted system is inherently going to be somewhat quieter in operation than a direct blow and because direct blow are most often found in smaller trailers it's not surprising one would assess a direct blow as being noisier as you're never that far away from it. My current Dometic Brisk II is direct blow and there's no question it's noisier than the ducted system I had in our previous KZ Spree.