I was having the same sound problem for the first week or so as well as having fps rates vary from 10-60. I would sometimes lose sounds while in explorable zones but most often it was after loading a new zone and pretty consistent in Lion’s Arch. This past weekend I upgraded my old Phenom II X2 550 to a (slightly newer) Phenom II X4 965. The older dual core was always running at or near 100% utilization when I was having sound or fps issues but since I’ve had the quad core cpu in I haven’t had either problem (even in WvW large fights). I also haven’t played since last night 9pm PST so I don’t know if I’d have the problem today.
This is pretty unscientific for sure and I wouldn’t suggest everyone upgrade their cpus (seeing how the X4 is still a fairly old processor) but could this be due to client optimization overall and not necessarily sound cards/drivers?