Oh, that's probably either the sound has either been EQ'd or they're two sounds layered on top of each other. Chances are, they're probably entirely synthesized, because you can make something that sounds almost exactly like that in SubTractor by 1st taking a Sine Wave, applying a Negative LFO Envelope, mapping the LFO to pitch, then turning on Noise. From there, you'd simply mess with the filters a bit, then apply reverb.
Because it's an active synthesizer, the Noise generated would likely sound different on each hit, creating a sense of natural variation, though you could probably expand upon that by taking certain measures.