It'll probably be better than a road junction most of the time, I used to live near a fairly big road junction in the capital and I nicknamed it "Cairo Junction" due to the number of times road drivers would sound their horn. I suspect much of it stemmed from either people being in the wrong lane and thereby cutting someone up, or people not merging properly since the main road through the junction had two lanes into one on both sides.
The only time there will be a lot of railway noise is if there are permanent way/engineering staff about. If the line stays open, there will be plenty of train horn noise (we are required to sound the train horn when we see staff on track), or if the line is closed there could be heavy machinery operating. If the place is right next to the station, expect to hear the somewhat quieter whine of traction motors.
At most places in London there's quite a lot of ambient noise, if the OP is looking for somewhere quieter, Kent/Sussex/Surrey might be a better choice, there's quite a few fast trains into Victoria/Blackfriars which won't take much longer than a Kent House stopper.