Welcome to the world of the "Good Guys"! Unless of course you're playing with Op Monsun, in which case I contradict myself and say "U-boats forever!"
I've never had that problem with the voices, so I'm not sure what's causing it but I am sure it's not normal. One thing you can do is use a free program like
www.goldwave.com to adjust all the voice levels. The program and others like it usually have "batch" adjustments so you can raise them all at once. That shouldn't be needed, though.
SH4 is great in its own way and a couple of the complaints about SH3 were addressed, mainly the crew now automatically rotates so you don't have to do it, and when General Quarters is called everyone goes on duty and the most qualified man for each post is put in charge. I find that very cool. On the other hand I wish there was something like SH3 Commander for SH4, mostly for the huge variety of crew names and for the ship names.
I also like your "Brag Page".