[MilCom] Aircraft Question

[Collins]

I've noticed some aircraft (which I believe may be C-21) doing touch & goes
at the airport, here.  The jet makes a noticeable "whistling" noise when it
goes overhead, a few miles from the airport (not quite as much as an A-10,
of course) but anyway, could this be JOSA flights ?  Just curious.  I've not
always heard them on the radio so I'm guessing they may be using VHF freqs.
Typically I lockout VHF approach & tower to filter commercial & private
planes.  Should I listen to these freqs also ?  

Thanks-

Collins
Fort Smith, AR