okay, couple of things here...the sound is from the flaps. You will hear it from different ac, depending on the flap location/size on the wing. The A320 has more of the outboard flaps, which run to almost the full length to the wing tips with a smaller inboard flap, while the B738, has large inboard flaps, and the flaps do not run as far out on the wing.
This has significant effect on the noise generated. (I have not observed any sound from speed brakes, unless its a FOQUA bust!)
In regards to wake vortex, the same principles apply. (while the vortex is generated near the wingtips, the wing tips do not generate the vortex)
AC that have outboard flaps, tend to generate a large core vortex. If you are standing under the flightpath, (best is about 1000m from threshold) this will sound like a deep, low roar...This is the larger volume, slower moving mass of air. For comparison, a 737-400 will make only a large core.
AC that have inboard flaps tend to generate a large core and small a core vortex. The small core is very high velocity, but dont last very long. These sound like tearing a piece of paper on breakup. In comparison, a 738 will make a large and small core vortex.
As misd-again pointed out, you can hear the differences between ac.
When you sit and study this, and observe 10 737-800's in a row, you can tell the difference in flap settings.
A380's are a kick to listen to...