I don't always hear it though, which means I wouldn't have thought it's the wheels.
Two notable occasions were when I was off to Imola to watch a Grand Prix in Italy and it was a RyanAir 737. We were landing in some pot-shed airport somewhere and had to weave between the hills.
Another occasion was when flying to the Dominican Republic in an Airbus. On the down leg we were so close to the runway I thought that perhaps there was another airport in front of us, but no, the captain banked sharply, turned tight, and then landed it.
The bang happens just before hard turning, almost like a hydraulic rudder is being activated for rear-steer because the bank was particularly hard. From my experience, typical 737/757 landing gear can be felt through the floor and then there's a thump as it locks in place. I'm sure it's not the same thing as the sound is different.
Last time I heard it I asked the attractive cabin lady what that noise was and she said softly "nothing to worry about, its normal" which I didn't want to hear. I'm a very technical person and want to know mechanically whats going on out of interest.
When the speed breaks kick in you can feel the plane shimmy and as I sit in the middle I tend to look for these so I'm not sure it's that either.
What a puzzle!