Not tried the 78 or A350 but the A 380 is extremely quiet
Back in the day tho rear engine jets were quiet on the inside but on the outside whoa.... A VC10 sounded like a whole squadron of Phantoms and made everything around you that could vibrate vibrate. And Caravelles could still be heard while they were miles away in the climb out
The 707 320C was quiet at flight idle in the descent but outside with gear and flaps down it emitted a piercing scream for the last few miles down the LHR glidepaths one of which passed right over a Cinema in Hounslow I used to frequent as a kid and seemed just as loud as standing in the street outside.
The MD80 series were the best balance of in and out noise for the rear engine generation although at the end off their careers the oddly nicknamed Mad Dogs were the noisiest when mixed in with the Minibuses and later 737s. Fantastic to fly in up front though with no engine noise at all and absolutely one of my favourites to fly on.
I never flew on a recip prop but living close to LHR back when the SW/NE runways in use there was a big variation in engine noise, I would say the powerful turbo compound engines on DC7Cs were quiet , DC6s didnt seem to be working their engines all that hard ( probably why they outlived all the others) Noisiest were Argonauts and Yorks with their snarling Merlins , the US radials were definitely much quieter.
A lot safer, faster, smoother and quieter today but back then spotting or just a keen interest saw a wonderful variety of types pass through LHR.