Connection / volume-level change sounds

WIN XP Home : my audio device is listed as "RealTek HD Audio output" -

My WIN XP sounds is "No Sounds"

I use VZAccess (Verizon air card) to access the www; when it connects, my system blasts out some kind of electronic sound -- can't call it a musical tone or beep or any such; talked at length with Verizon tech and there's nothing on their end of options/preferences that affects this; also, when I unloaded the RealTek drivers, the sound disappeared, so concluded it's a RealTek issue.

Similar (not same) loud tone/sound happens when I adjust the RealTek master volume slider.

QUITE annoying ... and very unwelcome.

Haven't been able to find any kind of options/preferences/etc. associated with RealTek, so am at a loss about how to get rid of this racket.

Any suggestions? Many thanks.