Listening to them give C-MED entry notifications, I would guess that it is the noise canceling microphones they use to block out the helicopter noise as opposed to being narrow band (which 11K2F3E is). This is from years (well before narrow band) of monitoring from the C-MED console. The audio is always crisp, but the level has always been a bit lacking.
I don't have an audio problem listening to them on my Radio [using a Vertex mobile as a UHF Scanner].
Medflight, LifeFlight, DART, Lifestar and Albany LifeFlight all loud and clear, routinely
Remember, many of the newer scanners can also do an Audio Boost on a Channel by Channel basis, give it a try.
10-04 on those noise cancelling Mic's. USCG Helo's are the same problem
ECPS, what frequencies do you use to listen to medflight etc?