When I play BZ II version 1.2 I have no issues, but this 1.3 patch ( yes I applied it over a fresh install ) I get repeating / echoing sound bytes. Why?
Try the /slowaudio command line switch.
another thing I noticed is that no matter how far away something is, the volume still is the same, wheather a chain gun bullet hits the ground 250 meters away or 2 meters away, it still sounds as if it thits the same distance away (always sounds really close). Same applies for all sounds I believe.
You have 3D Sound turned on? Also try adjusting the sound settings in Gameprefs.ini.
3d sound is turned on, everything is turned on, looking at gameprefs.
If you haven't already, make sure that you have the latest sound card drivers installed. The v1.3 patch redid all the audio code using DX8. Unfortunately, this may leave a lot of sound cards behind, if they are older and their drivers are not fully supportive of DX8.
If you've updated and you're still having trouble, you may have to try comparing software to hardware acceleration via the game's audio options. If software seems to solve some of the problems (though it may introduce others because of its emulation), my guess is that your sound card and/or it's drivers are just not delivering full compatibility.
My own experience has been that the WinXP drivers for Sound Blaster Live and Turtle Beach Santa Cruz did not handle all the sounds well. In particular, they had trouble with the hardware accelerated 2D sounds. I had better luck with my onboard sound chip and with an Audigy 2 ZS running WinXP. I think this is because the drivers for these last two sound solutions are more up to date.
Win98 drivers is another matter. To some extent, I have less trouble with Win98 drivers and older sound cards, but I'm not sure this means they are really fully supporting the DX8 sound features. They may just be faking it better. ;)