Why does the audio in my Mazda 3 randomly diminish?

I recently got a 2008 Mazda3, 5 speed manual transmission, and I've noticed that once in a while, like when I take a hard turn, or sometimes put the clutch in, or downshift, or accelerate quickly, or other random occurrences, the music I'm playing, whether it be from a CD, or Media like my iPhone, randomly diminishes to just the treble end of the music. Like the bottom half of the sound has just disappeared. It's not just music with heavy bass, just any music at all! All of the sudden, you I just lose half of the sound. I'm not complaining that my bass is too low, there's a setting to adjust that. I mean it is literally as if the sound is cut in half. It is not until I hit volume up or down does the fullness return, only to be diminished again shortly after, randomly, without my doing. Does anyone know why it does this? Do I need a new radio center unit thing? That would really stink because they're expensive and I just don't want to deal with that, or is there something in the car's manual I don't know of with some setting that random reduces what the output of the music is? I've tried the ALC feature or whatever it is, level 1, 2, and 3, and off, and it makes no difference. The audio still does this. Has anyone ever had this problem before? Any fixes?

Maybe it's too much stress on your battery? Do any cabin lights go dim when you do those things? Or is it just the head unit? (Radio center thingy)

Check all ground's for sure on any external amplifiers that may be in your ride, you don't even say if it's aftermarket or factory set up?