Excessive meowing after new upstairs neighbours moved in?
We have an 8-month ragdoll. He's always been "chatty" and likes to meow at us to initiate play, but the past two weeks something's changed and the meowing has gotten out of control. He still sleeps through the night just fine with us, and takes his usual long naps during the day, but when he's up and has some energy, the meowing is non-stop -- literally for half-hour or 45-minute periods without end, bordering on howling. He's perfectly healthy (vet checkup last week), litter/eating habits all the same -- the meowing is definitely directed at us, and seems to be some sort of anxious attention-seeking behaviour. He's only quiet when playing or cuddling. We're doing everything we can to ignore him when he's howling and reward him with play when he's silent, but this hasn't seemed to curb the habit.
We were trying to think of what it could be that started this behaviour, and the only thing we could come up with was environmental factors. At the beginning of December, we decorated our apartment for Christmas (a few small changes, but nothing major -- fake tree, so no scent), and also got new upstairs neighbours, who have 2 cats. These people actually used to live across the hallway from us, so I'm sure our cat "knows" their cats' scents, but I'm wondering if having two cats living above us now in our apartment might have been enough to trigger all of this new meowing? Has anybody had experience with something like this before?
Also, we're thinking about getting a feliway diffuser to see if that calms him down a bit.
Any advice would be great!