Most, if not all of the consumer level camcorders have AGC circuitry enabled (Auto Gain) with NO way to disable it. Pretty pitiful S/N as well.
Not sure what your input options are, I'm not familiar with the camera....but as others have mentioned, an external mic will help, albeit still a bit crippled by AGC. Not being familiar with the camera, there may be a way to shut it down. You'd have to check....
To have total control of your sound, capture it on an external recorder, IE Zoom H4n, Tascam DR-1/100, Marantz, Sony, etc all make SD handheld audio recorders....some with very high quality sound. Also, XLR jacks and 4 channel recording makes them extremely flexible and discreet.
Unfortunately, audio can make or break your film...as I'm sure is obvious to you. As well...one must spend over $3-4k* at this time to bypass AGC and have manual, in-camera control of his/her audio. Secondary system recording is definitely essential for decent audio control with your current rig....this is definitely not a BAD thing...in fact, it's common place in real world filmmaking. Gives you a chance to learn alot as well!
J
*Price for a camera with XLR and in camera audio control, EG...EX-1, HVX/HPX, XH-A, etc.